Scoliosis and Kyphosis - Clinical Tree

Scoliosis

The word scoliosis is derived from the Greek word meaning “crooked.” Scoliosis is defined as a lateral deviation of the normal vertical line of the spine. The lateral curvature of the spine also is associated with rotation of the vertebrae. This produces a three-dimensional deformity of the spine that occurs in the sagittal, frontal, and coronal planes.

The Scoliosis Research Society (SRS) recommends that idiopathic scoliosis be classified according to the age of the patient when the diagnosis is made. Infantile scoliosis occurs from birth to 3 years of age; juvenile idiopathic scoliosis, between the ages of 4 and 10 years; and adolescent idiopathic scoliosis, between 10 years of age and skeletal maturity. This traditional chronologic definition of scoliosis is important because major differences exist between the subtypes ( Table 44.1 ).

TABLE 44.1

Classification of Idiopathic Scoliosis by Age

Modified from Mardjetko SM: Infantile and juvenile scoliosis. In Bridwell KH, DeWald RL, editors: The textbook of spinal surgery , ed 2, Philadelphia, 1997, Lippincott-Raven.

Parameter	Infantile	Juvenile	Adolescent
Age at presentation	Birth to 3 yr	4-9 yr	10-20 yr
Male:female	1:1 to 2:1	<6 yr: 1:3 >6 yr: 1:6	1:6
Incidence	United States: 2%-3% Great Britain: 30%	United States: 12%-15% Great Britain: 12%-15%	United States: 85% Great Britain: 55%
Curve types	Left thoracic L:R (2:1) Left thoracic/right lumbar	Right thoracic R:L (6:1)	Right thoracic R:L (8:1)
Associated findings	Mental deficiency, congenital hip dysplasia, plagiocephaly, congenital heart defects	None	None
Risk of cardiopulmonary compromise	High	Intermediate	Low
Risk of curve progression	<6 mo: low >1 yr: high	67%	23%
Rate of curve progression	Gradual progression: 2-3 degrees/yr Malignant progression: 10 degrees/yr	Progression at puberty: 6 degrees/yr Malignant progression: 10 degrees/yr	1-2 degrees/mo during puberty
Curve resolution	<1 yr: 90% >1 yr: 20%	20%	Rare
Curve magnitude and maturity	Gradual progression: 70-90 degrees Malignant progression: >90 degrees	Progression at puberty: 50-90 degrees Malignant progression: >90 degrees	Curves >90 degrees are rare
Orthotic management	Effective at delaying and slowing rate of progression Ultimate progression: 100%	Decreases rate of progression until puberty (failure rate: 30%-80%)	Effectively controls curves <40 degrees (success rate: 75%-80%)
Surgical treatment	Instrumentation without fusion <8 yr After 8 yr: ASF-PSF After 11 yr: PSF	Instrumentation without fusion <8 yr After 8 yr: ASF-PSF After 1 yr: PSF	PSF with instrumentation ASF if younger than 11 yr with open triradiate cartilage
Risk of crankshaft	High	High	Low

ASF, Anterior spinal fusion; PSF, posterior spinal fusion.

Scoliosis also can be classified based on the cause and associated conditions. Idiopathic scoliosis is the most common type, but the exact cause of this type of scoliosis is not known. Congenital scoliosis is caused by a failure in vertebral formation or segmentation of the involved vertebrae. Scoliosis also can be classified based on associated conditions, such as neuromuscular disorders (cerebral palsy, muscular dystrophy, or other neuromuscular disorders), associated syndromes, or generalized disease (neurofibromatosis, Marfan syndrome, bone dysplasia, tumors, or as a result of irradiation).

A distinction should be made between early-onset and late-onset scoliosis because the deformity may affect cardiopulmonary development. During childhood, not only do the lungs grow in size, but also the alveoli and arteries multiply and the pattern of vascularity changes. The alveoli in the pulmonary tree increase by about 10-fold between infancy and 4 years of age and are not completely developed until 8 years of age. Scoliotic deformity limits the space available for lung growth, and children who develop significant scoliosis before the age of 5 years generally have disabling dyspnea or cardiorespiratory failure. Currently, according to the classification as it relates to treatment, some infantile and early juvenile curves are being identified as early-onset scoliosis.

Infantile Idiopathic Scoliosis

Infantile idiopathic scoliosis is a structural, lateral curvature of the spine occurring in patients younger than age 3 years. James, who first used the term infantile idiopathic scoliosis, noted that these curves occurred before 3 years of age, were more frequent in boys than in girls, and were primarily thoracic and convex to the left.

Wynne-Davies noted plagiocephaly in 97 children in whom curves developed in the first 6 months of life; the flat side of the head was on the convex side of the curve. Other associated conditions that she found were intellectual impairment in 13%, inguinal hernias in 7.4% of boys with progressive scoliosis, developmental dislocation of the hip in 3.5%, and congenital heart disease in 2.5% of all patients. This led her to believe that the etiologic factors of infantile idiopathic scoliosis are multiple, with a genetic tendency that is either “triggered” or prevented by external factors.

Infantile idiopathic scoliosis is more common in Europe than in North America. In the early 1970s, infantile scoliosis was seen in 41% of patients with idiopathic scoliosis in Great Britain compared with less than 1% in the United States. This difference was believed to be from infant positioning ( Fig. 44.1 ). Supine positioning was recommended in Europe, and prone positioning was recommended in the United States. Since the change to prone positioning, the incidence of infantile idiopathic scoliosis has declined in Great Britain from 41% to 4%.

FIGURE 44.1, Diagram illustrates postural molding of thorax when infant is laid supine and partly turned toward the side.

Most curves in infantile idiopathic scoliosis are self-limiting and spontaneously resolve (70% to 90%); however, some curves may be progressive, usually increasing rapidly, are often difficult to manage, and may result in significant deformity and pulmonary impairment. Unfortunately, when a curve is mild, no absolute criteria are available for differentiating the two types and predicting progression. James et al. found that those with resolving scoliosis generally had a deformity that was noted before 1 year of age; most had smaller curves at presentation, and none had compensatory curves. Lloyd-Roberts and Pilcher found that curves associated with plagiocephaly or other molding abnormalities were more likely to be resolving, indicating an intrauterine positioning cause of this scoliosis. According to James, when compensatory or secondary curves develop or when the curve measures more than 37 degrees by the Cobb method when first seen, the scoliosis probably will be progressive.

Mehta developed a method to differentiate resolving from progressive curves in infantile idiopathic scoliosis based on measurement of the rib-vertebral angle (RVA). She evaluated the relationship of the convex rib head and vertebral body of the apical vertebra by drawing one line perpendicular to the apical vertebral endplate and another from the midneck to the midhead of the corresponding rib; the angle formed by the intersection of these lines is the RVA ( Fig. 44.2 ). The RVA difference (RVAD) is the difference between the values of the RVAs on the concave and convex sides of the curve. Mehta reported that 83% of the curves resolved if the RVAD measured less than 20 degrees and that 84% of the curves progressed if the RVAD was greater than 20 degrees. She described a two-phase radiographic appearance based on the relationship of the apical ribs with the apical vertebra. In phase 1, the rib head on each side of the apical vertebra does not overlap the vertebral body. In phase 2, the rib head overlaps the convex side of the vertebral body. Phase 2 curves are progressive, and therefore the measurement of RVAD is unnecessary. These measurements are helpful in predicting curve progression, but the curves must be monitored closely to prevent severe progression with the resultant risk of restricted pulmonary disease. These measurements are helpful in predicting curve progression, but Corona et al. noted that these measurements should be used with care because of some variability of more than 10 degrees in 18% of paired observations. This highlights the necessity of closely monitoring curves both clinically and radiographically to prevent severe progression with the resultant risk of restricted pulmonary disease ( Fig. 44.3 ).

FIGURE 44.2, Construction of rib-vertebral angle (RVA) and rib–vertebral angle difference (RVAD). (1) Draw line parallel to bottom of apical vertebra (apical vertebral endplate). (2) Draw line perpendicular to line drawn in Step 1. (3) Find midpoint of head of rib. Find midpoint of neck of rib. These landmarks are estimated and mental note is taken. (4) Draw line from midpoint of head of rib to midpoint of neck of rib to line from Step 2. (5) Resulting angle is RVA for one side. (6) To calculate RVAD, calculate RVA for other side. Use lines created in Steps 1 and 2, and repeat Steps 3-5 for other side.

FIGURE 44.3, Two phases in progression of infantile scoliosis as seen on posteroanterior radiographs. Phase 1 : rib head on convex side does not overlap vertebral body. Phase 2 : rib head on convex side overlaps vertebral body.

An increased incidence of neural axis abnormalities (Chiari malformation, syrinx, low-lying conus, and brainstem tumor) has been noted on magnetic resonance imaging (MRI) in patients with infantile idiopathic scoliosis (21.7%). MRI evaluation is now recommended for infantile scoliosis for curves measuring more than 20 degrees. These patients usually require sedation for MRI. Pahys found a smaller percentage (13%) of patients with infantile scoliosis and intraspinal anomalies. Because of the need for sedation to obtain the MRI, close observation may be a reasonable alternative.

Treatment

Because of the favorable natural history in 70% to 90% of patients with infantile idiopathic scoliosis, active treatment often is not required. If the initial curve is less than 25 degrees and the RVAD is less than 20 degrees, observation with radiographic follow-up every 6 months is recommended. Most resolving curves correct by 3 years of age ( Fig. 44.4 ); however, follow-up should continue even after resolution because scoliosis may recur in adolescence.

FIGURE 44.4, A, Infantile scoliosis in 3-year-old child. B, At 4 years of age. C, At 6 years of age, curve has greatly improved and by 10 years of age (D) has resolved. E, At follow-up at age 16, there is no curve progression.

Casting

Treatment options for children with progressive infantile idiopathic scoliosis curves include serial casting, bracing, and later fusion; preoperative traction to correct the curve followed by fusion; and growing rod or vertical expandable prosthetic titanium rib (VEPTR) instrumentation without fusion (Synthes, West Chester, PA). Once the diagnosis of a progressive curve is made based on either a progressive Cobb angle or an RVAD of more than 20 degrees, rib phase 2, or a double curve, treatment is recommended. An orthotist can make a satisfactory thoracolumbosacral orthosis (TLSO) or cervicothoracolumbosacral orthosis (CTLSO) for curves that are not too large. Progression of many infantile curves can be prevented and significant improvement can be obtained with the use of a well-fitting orthosis during the early period of skeletal growth. In a very young child, serial casting with general anesthesia may be required until the child is large enough for a satisfactory orthosis. The interval between cast changes is determined by the rate of the child’s growth, but a cast change usually is required every 2 to 3 months. Brace wear is continued full time until the curve stability has been maintained for at least 2 years. At that point, brace wear can be gradually reduced. McMaster reported control of the curves in 22 children with infantile scoliosis with an average brace time of more than 6 years.

Sanders et al. reported good results with early casting for progressive infantile idiopathic scoliosis using the technique of Cotrel and Morel (extension, derotation, flexion) cast correction. Best results were achieved if casting was started before 20 months of age and in curves less than 60 degrees. Cast correction in older patients with curves of more than 60 degrees frequently resulted in curve improvement ( Fig. 44.5 ). Casts were changed every 2 to 4 months based on age and growth of the child. Once curves were corrected to less than 10 degrees, a custom-molded brace was used.

FIGURE 44.5, A and B, Mehta cast. C, Before cast wear. D, After 9 months of cast wear.

Casting for Idiopathic Scoliosis

A proper casting table is crucial for this procedure. Although a standard Risser frame will suffice, it is quite large for small children. Sanders et al. have designed a table that leaves the head, arms, and legs supported but the body free for cast application.

Technique 44.1

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Intubate the patient; thoracic pressure during cast molding can make ventilation temporarily difficult.
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Use a silver-impregnated shirt as the innermost layer. Head halter and pelvic traction also are used to assist in stabilizing the patient and in narrowing the body ( Fig. 44.6A ).
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A mirror slanted under the table is useful for viewing rib prominence, the posterior cast, and molds.
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Apply a thin layer of Webril with occasional felt on bony prominences.
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If there is a lumbar curve, flex the hips slightly to decrease lumbar lordosis and facilitate curve correction.
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Plaster is usually preferred over fiberglass because it is more moldable. The pelvic portion is the foundation of the cast and should be well molded.
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Apply pressure to the posteriorly rotated ribs with an attempt to anteriorly rotate these ribs to create a more normal chest configuration with counterrotation applied through the pelvic mold and upper torso. This is a derotation maneuver and should not push the ribs toward the spine in an attempt to correct the curve ( Fig. 44.6B ).
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If the apex is T9 or below, an underarm cast can be used, but the original technique used an over-the-shoulder cast.
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Create an anterior window to relieve the chest and abdomen while preventing the lower ribs from rotating. Create a posterior window on the concave side to allow the depressed concave ribs and spine to move posteriorly ( Fig. 44.6C ).

Operative treatment

If a curve is severe or increases despite the use of an orthosis or casting, surgical stabilization is needed. Ideally, surgery should not only stop progression of the curve but also allow continued growth of the thorax and development of the pulmonary tree. Growing rods can be used to control curve progression and still allow for growth of the spine ( ). This usually requires surgery every 6 months to lengthen the rods (see Technique 44.2 and ). The use of magnetically controlled growing rods (MCGR), such as the MAGEC Spinal Bracing and Distraction System (NuVasive, Aliso Viejo, CA), may help avoid a return for surgical lengthening every 6 months; however, these should be used in carefully selected patients because of the size and stiffness of the magnetic implants. Rib-based instrumentation, such as VEPTR, has been reported as another alternative to correct the curve and allow for continued growth of the spine, potentially decreasing the rate of autofusion seen with standard growing rods (see Technique 44.45). Schulz et al. reported this to be a safe and effective treatment of progressive curves in this patient population. When surgical fusion is necessary, a relatively short anterior and posterior arthrodesis should be considered, including only the structural or primary curve. Combined anterior and posterior arthrodesis is necessary to prevent the “crankshaft” phenomenon. The problem with this approach is that it leaves the child with a straight, shortened spine rather than a deformed spine of near-normal length. Karol reported that, despite early fusion surgery, revision surgery was required in 24% to 39% of patients. Restrictive pulmonary disease, defined as forced vital capacity less than 50% of normal, occurs in 43% to 64% of patients who have early fusion surgery. Thoracic growth after early surgery is an average of 50% of that seen in children with scoliosis who did not have early surgery. Because of the deleterious effect on the developing thoracic cage and lung function, fusionless instrumentation techniques are preferred.

Juvenile Idiopathic Scoliosis

Juvenile idiopathic scoliosis appears between the ages of 4 and 10 years. Multiple patterns can occur, but the convexity of the thoracic curve usually is to the right. Juvenile idiopathic scoliosis accounts for 12% to 21% of idiopathic scoliosis cases. The female-to-male ratio is 1:1 in children between 3 and 6 years of age. This ratio increases with age, with the ratio of 4:1 from 6 to 10 years of age, and reaches a female-to-male ratio of 8:1 by the time the children are 10 years of age. The natural history of juvenile idiopathic scoliosis is usually slow to moderate progression until the pubertal growth spurt. Lonstein found that 67% of patients younger than age 10 years showed curve progression and that the risk of progression was 100% in patients younger than 10 years who had curves of more than 20 degrees. Robinson and McMaster reported curve progression in 95% of children with juvenile idiopathic scoliosis. Of those patients followed to maturity, 86% required spinal fusion. Most juvenile curves are convex right thoracic curve or double thoracic curve patterns and closely resemble those of adolescent idiopathic scoliosis. Few patients with juvenile idiopathic scoliosis have thoracolumbar or lumbar curves. Dobbs et al. modified the adolescent idiopathic scoliosis classification system of Lenke for juvenile idiopathic scoliosis (see Fig. 44.33 ). (There are the same six curve types, but instead of using side-bending radiographs to distinguish structural from nonstructural minor curves the authors used the deviation from the midline of the apex of the curve from the C7 plumb line for thoracic curves and the center sacral vertical line (CSVL) for thoracolumbar and lumbar curves. If the apex of the curve is completely off the line, a structural minor curve is present; if the apex is not off the line, a nonstructural minor curve is present.)

As in infantile idiopathic scoliosis, a high incidence of neural axis abnormalities has been found on MRI in children younger than 11 years with scoliosis (26.7%). Some may argue about the need for MRI in a routine preoperative workup, but most would agree that specific factors indicating a need for further MRI evaluation include pain, rapid progression, left thoracic deformity, neurologic abnormalities (alterations in the superficial abdominal reflex), and other neurologic findings, such as loss of bowel or bladder control. If operative intervention is planned, then preoperative MRI evaluation is recommended.

Treatment

Although it is likely to progress and often requires surgery, juvenile idiopathic scoliosis is treated according to guidelines similar to those for adolescent idiopathic scoliosis. For curves of less than 20 degrees, observation is indicated, with examination and standing posteroanterior radiographs every 4 to 6 months. Evidence of progression on the radiographs as indicated by a change of at least 5 to 7 degrees warrants brace treatment. If the curve is not progressing, observation is continued until skeletal maturity.

Although much of the earlier literature concerning orthotic treatment of juvenile idiopathic scoliosis had emphasized the Milwaukee brace, a TLSO is used for thoracic curves with the apex at T8 or below. Initially, the brace is worn full time (22 of 24 hours). If the curve improves after at least 1 year of full-time bracing, the hours per day of brace wear can be decreased gradually to a nighttime-only bracing program, which is much more tolerable, especially when the child reaches puberty. However, the patient is carefully observed for any sign of curve progression during this weaning process. If curve progression is noted, a full-time bracing program is resumed.

The success of nonoperative treatment is variable; 27% to 56% require spinal fusion for progressive curves. It often is not possible to predict which curves will increase from the curve pattern, the degree of curvature, or the patient’s age at the time of diagnosis. Serial RVAD measurements have been useful to evaluate brace treatment; several guidelines can be formulated for evaluating brace treatment ( Box 44.1 ).

BOX 44.1

Evaluation of Brace Treatment of Juvenile Idiopathic Scoliosis by the Rib–Vertebral Angle Difference

RVAD , Rib–vertebral angle difference.

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If the RVAD values progress above 10 degrees during brace wear, progression can be expected.
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If the RVAD values decline as treatment continues, part-time brace wear should be adequate.
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Those patients with curves with RVAD values near or below 0 degrees at the time of diagnosis generally will require only a short period of full-time brace wear before part-time brace wear is begun.

Evidence of progression should be obtained before a brace is applied, unless the curve is greater than 30 degrees when the juvenile patient is first seen. Some curves, even in the range of 20 to 30 degrees, did not progress during a period of several months in one study; Mannherz et al. found progressive RVAD of more than 10 degrees over time to be associated with curve progression, and more frequent curve progression was noted in patients with less than 20 degrees of thoracic kyphosis. Double major curves tended to progress most often. Charles et al. reported that juvenile curves of more than 30 degrees had a 100% risk of progression to a surgical range, underscoring the importance of beginning treatment in curves of more than 30 degrees.

Kahanovitz, Levine, and Lardone found that patients who wore a Milwaukee brace part time (after school and at night) had good outcomes with curves of less than 35 degrees and RVADs of less than 20 degrees. Patients with curvatures of greater than 45 degrees at the onset of bracing and whose RVADs exceeded 20 degrees all eventually underwent spinal fusion. Patients with curvatures from 35 to 45 degrees at the onset of bracing had much less predictable prognoses. The part-time brace program consisted of wearing the brace after school and all night for approximately a year. The patients were then kept in the brace at night only for another 2.5 years. The brace was at that point worn every other night for an average of 1.2 years. Bracing generally was discontinued completely at an average of about 14 years of age. Individually, however, the number of hours spent wearing the brace depended on the amount of improvement and stability of the curvature. Part-time brace treatment may afford these children the social and psychologic benefits not provided by a full-time brace program. Jarvis et al. reported the successful management (prevention of surgery) with part-time bracing in patients with juvenile idiopathic scoliosis. The Milwaukee brace may be preferred because it does not cause chest wall compression in these young patients. A total-contact TLSO often is prescribed, but rib cage distortion is possible because of the lengthy time the child must wear the brace. Robinson and McMaster found that the level of the most rotated vertebra at the apex of the primary curve was the most useful factor in determining the prognosis of patients with juvenile idiopathic scoliosis. Patients who had a curve apex at T8, T9, or T10 had an 80% chance of requiring spinal arthrodesis by 15 years of age. Khoshbin et al. reported that 50% of their patients progressed to surgery despite brace treatment. The operative rate was higher for patients with curves of more than 30 degrees at the start of brace treatment.

Even if the curve progresses, bracing may slow progression and delay surgery until the child is older, which may avoid a short trunk and lessen the possibility of a crankshaft phenomenon. If orthotic treatment fails, operative management of the curve should be considered. Important considerations in the operative treatment of patients with juvenile idiopathic scoliosis are the expected loss of spinal height and the limited chest wall growth and lung development after spinal fusion. Another important consideration is the crankshaft phenomenon. With a solid posterior fusion, continued anterior growth of the vertebral bodies causes the vertebral body and discs to bulge laterally toward the convexity and to pivot on the posterior fusion, causing loss of correction, increase in vertebral rotation, and recurrence of the rib hump. Dimeglio found that during the first 5 years of life the spine from T1 to S1 grows more than 2 cm a year. Between the ages of 5 and 10 years, it grows 0.9 cm per year, and then it grows 1.8 cm per year during puberty ( Fig. 44.7 ). A solid spinal fusion stops the longitudinal growth in the posterior elements, but the vertebral bodies continue to grow anteriorly.

FIGURE 44.7, Growth velocity of T1-L5 segment, thoracic segment T1-12, and lumbar segment L1-L5.

There is no full agreement about the exact parameters for which a child requires anterior and posterior fusions to prevent crankshaft deformity ( Figs. 44.8 and 44.9 ). Shufflebarger and Clark recommended that patients with a Risser sign of grade 0 or 1, a Tanner grade of less than 2, and a significant three-dimensional deformity have a preliminary anterior periapical fusion before posterior instrumentation and fusion. Sanders et al. noted that 10 of 43 patients with triradiate cartilage developed a crankshaft deformity after posterior-only fusion. An open triradiate physis in the pelvis indicates the need for supplementary anterior fusion. With superior correction and rotational control available with pedicle screw instrumentation, perhaps the need for anterior fusions could be lessened.

FIGURE 44.8, Crankshaft phenomenon. A, Spine with scoliosis. B, Despite solid posterior fusion, continued anterior growth causes increase in deformity.

FIGURE 44.9, Fifty-seven-degree curve (A) was corrected to 39 degrees with posterior fusion and instrumentation (B) . C, Three years after surgery, deformity has recurred because of crankshaft phenomenon.

If the child is younger than 8 years, is small, and has a curve that cannot be controlled by nonoperative means, the ideal treatment is a growing rod system without fusion or growth modulation techniques. If the child is 9 or 10 years of age or large, growing rods or growth modulation may still be used but instrumentation and fusion may be appropriate. A combined anterior and posterior spinal fusion to avoid the crankshaft phenomenon may be needed, but with the use of pedicle screws to allow better correction and derotation of the spine, an anterior fusion may not be necessary.

Growing rod instrumentation

Growing rod instrumentation is a technique of posterior instrumentation that is sequentially lengthened to allow longitudinal growth while still attempting to control progressive spinal deformity.

Currently, growing rod techniques include the use of (1) a single growing rod, (2) dual growing rods, (3) VEPTR rods, (4) Luque trolley, and (5) Shilla technique. MCGR can help decrease the rate of surgical lengthening and can be used in a single- or dual-rod configuration, although a higher rate of rod failure occurs with single-rod instrumentation.

The growing rod techniques should be considered in a patient with significant growth remaining and a reliable family that will follow-up during treatment. This procedure usually is considered for patients younger than 10 years of age who have a curve of 60 degrees or more. Surgery typically is required every 6 months to lengthen the construct. A TLSO often is necessary for at least the first 3 to 6 months to protect the upper and lower levels of the instrumentation. Dual growing rods have been found to be effective in controlling severe spinal deformities and allowing spinal growth. With the use of dual rods, an apical fusion does not appear to be necessary during the course of treatment. Dual-rod techniques have been associated with a lower rate of complications than single-rod techniques, most commonly rod breakage and anchor failure.

Dual Growing Rod Instrumentation Without Fusion

A spinal instrumentation system that is appropriate for the child’s size is used and should include both pedicle screws and hooks for fixation. If the child weighs less than 30 lb, an infant spinal set may be necessary. If the infant set is used, the rod is quite flexible, and therefore some additional protection in the form of external immobilization is necessary until the system can be converted to a pediatric rod system of a larger diameter.

Technique 44.2

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Place the patient prone on the operating table or frame; prepare and drape the back in the routine sterile fashion.
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Take care to select the stable vertebrae at both ends of the curve and make a single, long, straight incision into the subcutaneous tissue from the upper to the lower neutral vertebrae. Alternatively, cranial and caudal incisions can be made over the end vertebrae and the rods can be tunneled between them. Dede et al. described preservation of motion segments by using the “stable-to-be vertebra” on bending or traction films as the lowest instrumented vertebra. The stable-to-be vertebra is the vertebra that is transected by the center sacral line on traction or bending films ( Fig. 44.10 ).
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Confirm appropriate levels with a radiograph.
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Carry the dissection down to the lamina and spinous process of the end vertebrae.
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Strip the periosteum from the concave and convex lamina out to the facet joint of the two vertebrae selected for instrumentation at each end of the curve.
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The upper and lower foundations for the growth rods can be done with either pedicle screws or hooks. If pedicle screws are used, especially in the upper thoracic spine, the use of a sublaminar wire or tape at the same level can be helpful in preventing axial pullout of the screws. If hooks are used to form the upper claw, insert a pedicle hook onto the lower of the two upper vertebrae and another superior transverse process hook on the upper of the two vertebrae on both the concave and convex sides.
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Form the lower claw by placing a supralaminar hook on the upper vertebra and the infralaminar hook on the lower vertebra. If it is anatomically feasible, pedicle screw fixation can be used in both the upper and lower foundations.
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Use two rods on the concave side and two rods on the convex side.
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Contour the rods to the natural contours of thoracic kyphosis and lordosis.
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Insert the rods under direct vision and use the appropriate set screws to hold the rods in the hooks or pedicle screws. Alternatively, tunnel the rods between the two incisions using a chest tube for guidance and to prevent intrathoracic penetration of the rod.
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Join the rods together with a low-profile growth rod connector ( Fig. 44.11 ).
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Use local autograft and allograft bone to pack around the upper and lower foundation sites.
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Do not attempt subperiosteal dissection between the hook sites to minimize the risk of autofusion.

Postoperative Care

The child is placed in an orthosis for the first 6 months depending on the quality of the anchor fixation. At that time, the orthosis can be discontinued if the anchor sites are solidly fused. The rods routinely are lengthened every 6 months depending on the growth rate of the child. Lengthening is performed by exposing the connector and loosening the set screws. Distraction is applied, and the set screws are retightened. Lengthenings are stopped when no further distraction can be achieved. Sankar et al. found that with successive lengthenings, there is a law of diminishing returns: repeated lengthenings had decreased gains in length with each subsequent lengthening over time. When no further distraction can be achieved, patients have typically undergone “final arthrodesis.” This usually necessitates removal of the rods, and in our experience, if the proximal and distal anchors are still solidly fixed and well fused, they can be used as part of the final construct ( Figs. 44.12 and 44.13 ). “Final arthrodesis” in this setting has been associated with very little curve correction and a high complication rate. For this reason, patients with good deformity correction, sagittal and coronal balance, and well-fixed implants may be able to be observed with implants in place.

FIGURE 44.12, A, Posteroanterior radiograph of child with infantile scoliosis treated with dual growing rods (B).

FIGURE 44.13, Growing rods. SEE TECHNIQUE 44.2.

Other growing rod constructs include the Luque trolley and the Shilla technique. These techniques allow apical control while guiding the growth of the spine along the rod system. The Luque trolley consists of sublaminar wires and rods without fusion. The Shilla technique consists of a nonlocking pedicle screw implant. The apex of the deformity is fixed and fused with pedicle screws while the ends of the construct are instrumented with screws that are not locked to the rod. This theoretically allows for apical control of the deformity and continued axial lengthening of the spine with growth. While techniques such as that of Shilla have been shown to decrease the number of surgical episodes for patients, concerns exist about wear debris and implant prominence.

Shilla Guided Growth System

Technique 44.3

(MCCARTHY ET AL.)

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Careful assessment of upright coronal and sagittal films, along with analysis of the flexibility of the curve by bending or traction films, is necessary to determine the location of the apical vertebral segments ( Fig. 44.14 ). The apical three or four vertebral segments that are least corrected through flexibility testing are the apical levels for fusion and maximal correction.
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Place small needle markers in the spinous processes and obtain a radiograph to identify spinal levels.
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Make a single midline incision and perform subperiosteal dissection to only the apical levels.
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Incise the fascia 1 cm off the midline on both sides of the spinous processes from cephalad to caudad, merging with the subperiosteal dissection at the apex.
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Place bilateral fixed-head pedicle screws throughout the apical levels.
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Perform Ponte osteotomies (see Technique 44.24) between the apical segments if needed to enhance correction in all planes. Apical decortication is necessary for fusion of these levels.
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Place the growth guidance screws through the muscular layer with fluoroscopic visualization of bone. Use a cannulated polyaxial screw of sufficient diameter to fill the pedicle. A Jamshidi trocar system is helpful in placing the screw in the center of the pedicle.
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The location of the guidance screws depends on the curve; the screw should extend far enough into the lumbar spine to maintain the lordosis and coronal correction. Avoid stopping the caudal instrumentation at the thoracolumbar junction because this may lead to prominence with flexion.
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Place the guidance screws at bilateral locations or staggered, making sure that they are separated by enough distance on the rod to allow for easy sliding.
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Because the guidance screws at the top of the construct are subjected to pull-out forces from kyphosis, place a sublaminar or transverse process cable or FiberWire (3 mm) one level above the upper screws to protect them.
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Choose a rod of the appropriate diameter for the size of the child, generally 4.5 mm, and contour it into normal sagittal curves, leaving the rod one vertebral level long at each length for growth.
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Before placement of the permanent rods, place a temporary (provisional) rod on the convex side and attach it loosely at the apex and one growing screw above and below the apex.
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Roll the provisional rod into a neutral position in the coronal and sagittal positions, translate it toward the concavity of the curve with coronal benders, and hold it there by tightening the apical plugs.
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Attach the permanent concave rod to the screws and remove the provisional rod.
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Derotate the apical levels with tube derotation devices or a vertebral column derotation device while holding the rods in place with vise grips to prevent rod rotation.
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The fixed-head screws lock the rods at the apical screws through the locking set screws that fix to the rods. The guidance screw caps capture the rods in the guidance screw head, leaving room for movement of the rod within the screw head.
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If needed to help maintain rod rotation, use a crosslink just below the apical fixation. If the child is younger than 5 years old, use a sliding type of crosslink to allow for growth in the canal diameter.
▪
Use the torque/countertorque device to snap off the caps at a preset torque pressure.
▪
Place bone graft at the apex only.
▪
Close the wound in routine fashion, using a small drain if necessary.

Postoperative Care

The child is immobilized for 3 months. A bivalved form-fitting turtle-shell brace is used during daytime until the apical fusion is solid. A protective brace is not necessary after this period of immobilization unless excessively vigorous activities are expected.

Growing rods do have potential complications, and complications are common. Bess et al. found at least one complication in 58% of patients with early-onset scoliosis who were treated with growing rods; submuscular placement of the rod resulted in fewer complications than subfascial placement. The most common complications are (1) rod breakage, (2) hook displacement or failure of proximal or distal fixation points, (3) infection, (4) skin breakdown over prominent rods, and (5) autofusion of the spine. Cahill et al. reported autofusion in 89% of children treated with growing rods. Arthrodesis after growing rod treatment has been associated with minimal curve correction in the coronal and sagittal planes, minimal gain in thoracic height, and a complication rate approaching 30% due primarily to spine stiffness, osteopenia from stress shielding, and infection from multiple previous surgical lengthenings. For these reasons, it may be reasonable for patients with well-balanced curves to be observed long term with their implants left in place, avoiding the risks of arthrodesis. A follow-up study of 100 patients treated with growing rods found that at 4-year follow-up, there was a 20% rate of unplanned return to the operating room, primarily for infection, device problems, and curve progression, highlighting the fact that “final arthrodesis” may not be final.

Rib-based instrumentation systems such as VEPTR can be used as a growing rod system (see Technique 44.45). The constructs can be rib-to-rib, rib-to-spine, or rib-to-pelvis. This has the advantage of minimal exposure of the spine and a theoretical decreased risk of spontaneous fusion of the spine. Another technique is to use a claw construct around ribs to act as the proximal attachment for dual growing rods. The advantage to using ribs as anchors instead of the spine is the preservation of motion between vertebrae, thereby preventing or delaying spontaneous fusion. The procedure is contraindicated in patients with kyphosis (upper thoracic kyphosis is poorly controlled with rib anchors) and patients who cannot tolerate repeated surgical procedures. This technique uses traditional spine implants with hooks that fit around the ribs. It is important to place the hook as close as possible to the transverse process to prevent the hook from sliding laterally ( Fig. 44.15A,B ). The rate of proximal (rib) anchor failure is inversely related to the number of rib anchor points, and ideally six to eight rib anchors (three or four on each side) should be used. Outriggers often can be used to increase the number of anchor points as well ( Fig. 44.16 ).

FIGURE 44.15, A, Model of thoracic spine with ribs. Correct placement of rib anchors (white arrows) lateral to tips of transverse processes (black arrows). B, Dissection of soft tissue anterior to rib. SEE TECHNIQUE 44.4.

FIGURE 44.16, Anterior-posterior and lateral radiographs of 8-year-old girl with neuromuscular scoliosis and rib-based fixation with outriggers. A, Note that outriggers allow increased number of rib anchor points. B, Use of specialized rib cradles allows fixation of multiple ribs in same cradle, increasing strength of anchor.

Growing Rod Attachment Using Rib Anchors

Technique 44.4

(SANKAR AND SKAGGS)

▪
Position the patient prone, taking care to pad all bony prominences. Neuromonitoring is essential when performing this procedure and should include both the upper and lower extremities because of the proximity of the upper instrumentation to the brachial plexus when the second and third ribs are used. Fixation to the first rib should be avoided.
▪
Make a midline skin incision or two separate incisions at the top and bottom of the construct, depending on the surgery.
▪
Dissect through the subcutaneous tissues and elevate a flap superficial to the paraspinal muscles laterally past the transverse processes. Confirm the location fluoroscopically.
▪
Alternatively, if the patient has multiple fused ribs and an open thoracostomy is planned, place the patient in the lateral decubitus position. Make a curvilinear J-shaped incision, starting halfway between the medial edge of the scapula and the posterior spinous process of T1-T2. Carry the incision distally and laterally across the 10th rib. Transect the muscle layers in line with the skin incision down to the level of the ribs and elevate an anterior flap to the costochondral junction. The paraspinal muscles are elevated from lateral to medial to the tips of the transverse process. In patients with multiple rib fusions and stiff chest walls, an opening wedge thoracostomy is indicated.
▪
For most patients, a thoracostomy usually is not necessary and has been shown to disrupt pulmonary function. The use of distraction-based rib implants is effective in opening up the rib spaces. Standard spine hooks can be used. Make a 5-mm transverse incision just distal to the neurovascular bundle using cautery (lateral to the transverse process). Make sure that the dissection on the top of the rib is immediately adjacent to the transverse process only (see Fig. 44.15A ). If the soft tissues are dissected too far laterally, hooks tend to slide down. Use a Freer elevator to dissect the soft tissue anterior to the rib (see Fig. 44.15B ). Preserve the periosteum around the rib to allow the rib to hypertrophy in response to stress.
▪
If a specialized device cradle is necessary, use a similar insertion technique, except stay subperiosteal with the rib dissection. Use a Freer elevator in both a superior and inferior direction around the rib to create a channel. Insert the rib cradle cap into the superior end of the channel and the rib cradle into the inferior end of the channel. Align the two devices and connect them with the cradle cap lock.
▪
Place a conventional upgoing spinal hook into the interval between the periosteum and pleura using a standard hook inserter or partial rod. Usually a second upgoing hook is placed around an adjacent rib to share the load.
▪
After proximal fixation, attention is turned to placement of the distal anchor. Through the same incision, subperiosteally dissect the lamina of the intended vertebrae. Either single-level fixation with a downgoing supralaminar hook or, more commonly, two-level fixation with pedicle screws can be used. If single-level fixation is used, preserve the interspinous ligament to avoid progressive kyphosis of the distal segment with distraction. If pedicle screws are used, place them at two adjacent levels because plowing of the implants could injure nerve roots.
▪
If two-level distal anchoring is chosen, use a narrow rongeur to destroy the facet joint and place cancellous crushed allograft into the joint. Decorticate the exposed bone and place bone graft before the rod to maximize bony contact.
▪
If one incision was used and if separate upper and lower rods were used, they can be connected with a longitudinal growing rod connector or side-to-side connector with the rods overlapping. It is prudent to use more than one connector. If two separate incisions were used for exposure, a soft-tissue tunnel should be made between the two anchor sites for passage of the rods using a chest tube to facilitate safe passage of the rod.
▪
Although unilateral rods are less invasive, there are fewer anchor points to share the load, and balancing the curve can be problematic. Dual rods are more stable and less prone to breakage and loss of fixation and make balancing the spine easier. When dual rods are used, a crosslink should be avoided because, although biomechanically more stable, use of a crosslink has been associated with catastrophic spinal cord injury when screw pull-out occurs. Screw pull-out with a crosslink typically occurs posteriorly along the axis of the pedicle, avoiding the spinal cord. The crosslink will not allow the screw to pull out along the trajectory of the pedicle and can pull out directly into the spinal cord.
▪
If an opening wedge thoracostomy was performed, a second rib-to-rib device can be used laterally to assist in correction and to reduce the load on the medial rib-to-spine device. Place the superior cradle around the same ribs that have the medial hybrid device and place the inferior cradle on a stable rib no lower than the 10th rib.
▪
Before wound closure, fill the upper anchor site with warm saline and perform a Valsalva maneuver to look for a pleural leak. If bubbles are present, place a Hemovac (Zimmer, Inc., Warsaw, IN) or chest tube into the pleural space for a few days.
▪
Close the wound in layers using 1-0 braided absorbable suture for the musculocutaneous flap, a 2-0 suture for the dermis, and a running 3-0 monofilament absorbable suture for the final subcuticular layer.

Postoperative Care

Physical therapy is started on the first day after surgery. A TLSO should be used for 3 months if the arthrodesis was at a distal anchor site. Patients may return to sports at 3 months. Lengthenings are planned for every 6 months after the initial surgery.

Guided growth and physeal stapling

Growth modulation is an attempt to apply the principles of guided growth in the lower extremities with physeal stapling. Intervertebral stapling is used to produce a tethering effect on the convex side of the spine. This tether theoretically will allow for continued growth on the concave side of the spine deformity and gradual correction of the deformity with growth. Devices that have been used for this growth modulation are a flexible titanium clip, a nitinol staple, and, more recently, an anterior spinal tether using anterior vertebral body screws and a polypropylene cord.

Anterior Vertebral Tethering

With the development and FDA approval of anterior vertebral tethering, the use of vertebral body stapling has dropped dramatically. Purported advantages of anterior vertebral tethering over posterior spinal fusion include that it allows the spine to grow and remain flexible, it is one-time surgery, and a later fusion can be done if needed. The indications for this technique have not been well established, but it is most likely beneficial for patients with enough growth remaining to substantially alter the shape of the spine and is most suited for primary thoracic curves with typical hypokyphotic apices ( Fig. 44.17 ). Suggested contraindications include patients with no remaining growth, patients younger than 8 years of age, patients with curves of less than 40 degrees or more than 65 degrees, and patients with left-sided curves, pulmonary disease limiting single-lung ventilation, previous ipsilateral chest surgery, or poor bone quality.

Technique 44.5

▪
With the use of single-lung ventilation and the patient in the lateral decubitus position, make a thoracoscopic approach.
▪
With fluoroscopy, mark the screw trajectories in the coronal plane, planning for three posterior axillary line 15-mm portals for screw placement. Use an 11-mm anterior axillary line portal for endoscopic placement.
▪
Open the pleura longitudinally 1 cm anterior to the rib heads.
▪
Coagulate and divide the segmental vessels and retract them anteriorly with sponges placed between the spine and the great vessels.
▪
Place bicortical transverse vertebral body screws through pronged washers using fluoroscopy to guide the screw trajectory.
▪
Introduce the tethering cord through a portal and capture it with a set screw into the proximal vertebral body screw. Adjust the portals to the appropriate interspace used to place the adjacent screws, and remove the long end of the tether from the chest through that portal, allowing a tensioning device to take slack out of the tether as the next set screw is tightened.
▪
Repeat this sequence for each screw, with more or less compression applied as indicated based on the deformity (generally more compression at the apex and less to none at the ends).
▪
Cut the tether distally and close the pleura over the device with the endoscopic suturing technique. Place a chest tube and reinflate the lungs.

Postoperative Care

The patient recovers in the hospital for 4 to 5 days. A thoracolumbosacral orthosis is recommended for 3 months after surgery. Noncontact activities can be resumed after 3 months.

FIGURE 44.17, A, Anterior vertebral body tethering. B, Before tethering. C, After tethering. SEE TECHNIQUE 44.5.

Instrumentation with fusion

If a child is older than 9 or 10 years or is unable to cooperate with the demands of growth rods, instrumentation and spinal fusion should be considered. A combined anterior and posterior procedure should be considered if the patient is deemed at risk for the crankshaft phenomenon (see Figs. 44.7 and 44.8 ). However, with the use of pedicle screw fixation and the ability to get better correction of vertebral body rotation and the Cobb angle, an anterior fusion rarely is used.

Preferably, if an anterior procedure is performed, the anterior release and fusion are done without sacrificing the segmental vessels. Anterior instrumentation is not used if posterior instrumentation is scheduled as a second procedure. Posteriorly, a multiple-hook or pedicle screw segmental system is most commonly used. Many of these systems have a variety of different size hooks, pedicle screws, and rods, depending on the size of the child. Karol et al., however, found that patients with proximal thoracic deformity who required fusion of more than four segments, especially the upper thoracic, were at higher risk for the development of restrictive pulmonary disease. There was a significant correlation between poor pulmonary function and the proximal level of the thoracic fusion and the percentage of thoracic vertebrae fused.

Adolescent Idiopathic Scoliosis

Adolescent idiopathic scoliosis is present when the spinal deformity is recognized after the child is 10 years of age but before skeletal maturity. This is the most common type of idiopathic scoliosis. The characteristics of adolescent idiopathic scoliosis include a three-dimensional deformity of the spine with lateral curvature plus rotation of the vertebral bodies. Most idiopathic curves are lordotic or hypokyphotic in the thoracic region, and this may represent an important factor in the etiology of idiopathic scoliosis.

Etiology

The exact cause of idiopathic scoliosis remains unknown. The consensus is that there is a hereditary predisposition and its actual cause is multifactorial. There are many proposed etiologic factors, but these can be divided into six general categories: (1) genetic factors, (2) neurologic disorders, (3) hormonal and metabolic dysfunctions, (4) skeletal growth, (5) biomechanical factors, and (6) environmental and lifestyle factors. The role of a genetic component in the cause of scoliosis is supported by several studies demonstrating an increased incidence of scoliosis in family members. Riseborough and Wynne-Davies found scoliosis in 11% of first-degree relatives of 207 patients with scoliosis. Genetic studies of families in which multiple members are affected have suggested several sites within the genome that appear to be linked to scoliosis. Currently genetic testing is being evaluated as a prognostic test for the risk of curve progression. Abnormalities in the central nervous system also have been thought to play a role in causing scoliosis. These neurologic factors can be divided into two major groups: neuroanatomic and neurophysiologic dysfunction. Studies have reported anatomic abnormalities in the midbrain, pons, and medulla and the vestibular system in scoliosis patients. Hindbrain abnormalities with cervicothoracic syrinx and low-lying cerebellar tonsils, with or without an abnormal cerebrospinal fluid dynamic, have been reported in patients with adolescent idiopathic scoliosis. Abnormalities of equilibrium and vestibular function have been noted as a possible cause. Differential growth between the right and left sides of the spine and a relative overgrowth of the anterior spinal column compared with the posterior column, resulting in a relative thoracic lordosis, have been postulated to cause scoliosis. Hormone abnormalities that have been proposed as causes are abnormalities in growth hormone, estrogen, melatonin, calmodulin, and leptin. Biomechanical causes are thought to be a result of asymmetric loading of the immature spine, which in turn causes asymmetric growth, resulting in a progressive deformity. Possible environmental or lifestyle factors include nutrition, diet, calcium and vitamin D intake, and exercise level. In summary, the exact cause of scoliosis remains unknown and may be multifactorial. Current research continues to try to better define these proposed causes.

Natural history

A knowledge of the natural history and prevalence of idiopathic scoliosis is essential to determine if treatment is necessary. Three important questions need to be answered:

What is the prevalence of idiopathic scoliosis in the general population?
What is the likelihood of curve progression necessitating treatment in a child with scoliosis?
What problems may occur in adult life if scoliosis is left untreated and the curve progresses?

Idiopathic scoliotic curves of more than 10 degrees are estimated to occur in 2% to 3% of children younger than 16 years of age. Larger curves of more than 30 degrees are estimated to occur in 0.15% to 0.3% of children. Weinstein created a table of calculations that show decreasing prevalence with increasing curve magnitude ( Table 44.2 ). The importance of these prevalence studies is that small degrees of scoliosis are common but larger curves occur much less frequently. Fewer than 10% of children with curves of 10 degrees or more require treatment.

TABLE 44.2

Adolescent Idiopathic Scoliosis Prevalence

From Weinstein SL: Adolescent idiopathic scoliosis: prevalence and natural history. In Weinstein SL, editor: The pediatric spine: principles and practice , New York, 2001, Raven.

Cobb Angle (Degrees)	Female:Male	Prevalence (%)
>10	1.4-2:1	2-3
>20	5.4:1	0.3-0.5
>30	10:1	0.1-0.3
>40		<0.1

Once scoliosis has been discovered in a child, the curve must be evaluated for the probability of progression, defined as an increase of 5 degrees or more measured by the Cobb measurement over two or more visits. What is unknown is whether this progression will continue and what the final curve will be. Spontaneous improvement is rare, occurring in 3% of adolescents with idiopathic scoliosis, most of whom have curves of less than 11 degrees. Certain factors have been found to be related to curve progression ( Box 44.2 ). Progression is more likely in girls than in boys. The time of curve progression in adolescent idiopathic scoliosis generally is during the rapid adolescent growth known as the peak height velocity (PHV), which usually occurs before menses in females and is about 8 cm per year for girls and 9.5 cm per year for boys. The incidence of progression decreases as the child gets older and approaches skeletal maturity. The incidence of progression also has been found to be related to curve patterns. In general, double curves are more likely to progress than single curves and single thoracic curves tend to be more progressive than single lumbar curves. The incidence of progression also increases with the curve magnitude. Bunnell estimated that the risk of progression for a 20-degree curve is approximately 20% and the risk for a 50-degree curve is 90%, and Sanders developed a chart to predict progression of a curve when a patient is first seen ( Fig. 44.18 ). Historically, the Risser staging based on the ossification of the iliac crest was used to assess skeletal maturity and subsequent risk of curve progression. While simple and readily available on routine spine radiographs, its reliability has been questioned because of the variability of ossification of the iliac crest apophysis and the fact that Risser staging correlates poorly to predicting PHV. Sanders et al. developed a simplified classification of skeletal maturity based on hand radiographs that has been shown to correlate highly with curve behavior ( Fig. 44.19 ). The natural history of adolescent idiopathic scoliosis in adulthood is difficult to study because of the challenges in obtaining long-term follow-up data. In general, patients with smaller curves, less than 30 degrees, will do well in adulthood with little or no associated morbidity.

BOX 44.2

Factors Related to Progression of Adolescent Idiopathic Scoliosis

▪
Girls > boys
▪
Premenarchal
▪
Risser sign of 0
▪
Double curves > single curves
▪
Thoracic curves > lumbar curves
▪
More severe curves

FIGURE 44.18, Logistic projection of probability of Lenke type I and type 3 curves progressing to surgery assuming greater than 50-degree threshold.

FIGURE 44.19, Sanders classification of skeletal maturity.

The incidence of back pain in the general population is between 60% and 80%, and the incidence in patients with idiopathic scoliosis is comparable. Patients with lumbar or thoracolumbar curves, especially those with translatory shifts at the lower end of the curves, have a slightly greater incidence of backache than patients with other curve patterns, but this is rarely disabling and is unrelated to the presence of osteoarthritic changes on radiographic examination.

In a 50-year follow-up study, the incidence of back pain in scoliosis patients was 77% compared with 37% in control subjects. Chronic back pain was reported by 61% of the scoliosis group and 35% of the control subjects. However, the ability of scoliosis patients to perform activities of daily living and work was similar to that of the control subjects. The location of pain has been variable in studies and generally unrelated to the location or magnitude of the curve. In contrast, lumbar and thoracolumbar curves may arise in adult life and cause severe pain and discomfort. This degenerative type of scoliosis should not be confused with the natural history of untreated adolescent idiopathic scoliosis. Ultimately, it is important to determine whether the pain is related to scoliosis before treatment determinations are made.

A direct correlation has been noted between decreasing vital capacity and increasing curve severity due to restrictive lung disease and is seen in large thoracic curves, greater than 100 degrees. One study found significant respiratory impairment (pulmonary function <65% predicted) in 19% of their preoperative patients with adolescent idiopathic scoliosis. The decrease in pulmonary function correlated with the severity of the main thoracic curve and sagittal plane hypokyphosis and was seen in patients with curves of 70 to 80 degrees. Death in patients with adult idiopathic scoliosis also seems to be related to thoracic curves greater than 100 degrees, with resultant cor pulmonale. With modern surgical techniques, death from cor pulmonale from adolescent idiopathic scoliosis is extremely rare.

The psychologic effect of scoliosis has been studied by numerous authors. Unhappiness with the appearance often is correlated with the size of the rib prominence. Middle-aged patients tolerate the psychologic effects of scoliosis better than teenagers; however, many adult patients seeking treatment for untreated adolescent idiopathic scoliosis are most concerned with the cosmetic aspects of the disorder.

Curves may continue to progress throughout adult life. Weinstein et al. identified multiple factors that predict the likelihood of curve progression after maturity ( Table 44.3 ). In general, curves in any area of less than 30 degrees at skeletal maturity did not tend to progress in adult life. Larger curves were more likely to progress throughout adult life, especially thoracic curves between 50 and 75 degrees. Lumbar curves also tend to progress in adulthood in curves less than 50 degrees if they are accompanied by a transitory shift between the lower vertebrae.

TABLE 44.3

Progression Factors in Curves More Than 30 Degrees at Skeletal Maturity

From Weinstein SL: Natural history, Spine 24:2592, 1999.

Thoracic	Lumbar	Thoracolumbar
Cobb >50 degrees	Cobb >30 degrees	Cobb >30 degrees
Apical vertical rotation >30 degrees	Apical vertical rotation >30 degrees	Apical vertical rotation >30%
Mehta angle >30 degrees	Curve direction Relation L5 to intercrest line Translatory shifts	Translatory shifts

Patient evaluation

The initial evaluation of the patient should include a thorough history, physical and neurologic examinations, and spine radiographs.

Most patients with scoliosis present for evaluation because of the appearance of their spine deformity. The prevalence of back pain for most adolescent idiopathic scoliosis patients is similar to that in the general population. Further workup may be needed if the patient’s back pain is persistent, interferes with daily activities, occurs at night, or is associated with any abnormal neurologic findings. Menarchal status, patient and parental height, and family history of scoliosis should be determined. Scoliosis occurs three times more frequently in children whose parents are affected and seven times more frequently if a sibling is affected. Also, if the parents or siblings have been treated for scoliosis, this may suggest a greater likelihood of curve progression in the patient. Surgical history is important in identifying scoliosis associated with congenital heart disease or with a prior thoracotomy.

On physical examination, the height of the patient should be measured. Serial measurement of height will detect when PHV is occurring associated with an increase in progression of the curve. The best clinical test for evaluating spinal curvature is the Adams forward bending test ( Fig. 44.20 ). As the patient bends forward at the waist until the spine is horizontal, the trunk is observed for rotation from behind (to assess midthoracic and lumbar rotation) and from the front (to assess upper thoracic rotation). The knees should be straight, the feet together, the arms dependent, and the palms in opposition. Because of vertebral rotation, this will produce a rib prominence in the thoracic region or a paraspinal fullness in the lumbar region. An angle of more than 7 degrees is considered abnormal and usually correlates with a curve of 15 to 20 degrees. The sagittal plane should also be examined for excessive kyphosis or lordosis. Limb lengths should be evaluated because a discrepancy may cause a pelvic tilt and a compensatory scoliosis.

FIGURE 44.20, Adams forward bending test. Note right thoracic rib prominence and left lumbar prominence in patient with thoracolumbar curve.

On inspection of the spine, the examiner should look for any dimpling ( Fig. 44.21 ), hair patches, or skin abnormalities, such as hemangiomas or café au lait spots. Asymmetry of the shoulder, scapula, ribs, and waistline should be noted. Spinal balance can be determined by the alignment of the head over the pelvis. The head should be positioned directly above the gluteal crease. This can be assessed by dropping a plumb line from the base of the skull or from the spinous process of C7. The plumb line should not deviate from the center of the gluteal crease by more than 1 to 2 cm. In the sagittal plane, the spine is usually hypokyphotic. If hypokyphosis is absent clinically and radiographically, then a syrinx should be ruled out by MRI. A thorough neurologic examination should be done to determine if an intraspinal neoplasm or a neurologic disorder is the cause of scoliosis. Particular attention should be given to the abdominal reflexes because often they are the only neurologic abnormality found with some intraspinal disorders.

FIGURE 44.21, Sacral dimple may be sign of congenital scoliosis.

Radiographic evaluation

Posteroanterior and lateral radiographs of the spine, including the iliac crest distally and most of the cervical spine proximally, should be made with the patient standing. Inclusion of the iliac crest and the cervical spine generally requires 14 × 36-inch cassettes or digital equipment that allows accurate splicing of images. Patients should stand with their knees locked, with feet shoulder width apart, and looking straight ahead. The patient’s shoulders are flexed forward, the elbows are fully flexed, and the fists should rest on the clavicles. The organs most at risk from radiation are the maturing breasts, and radiation is decreased by a factor of 5 to 11 by use of the posteroanterior view. Faster radiographic film and rare-earth screens also reduce the patient’s exposure to radiation. New low-dose, digital slot-scanning techniques require approximately one eighth the radiation of standard radiographs and allow the creation of three-dimensional models to aid with surgical planning when necessary.

Although no absolutely accurate method is available for determining skeletal maturity as an adolescent progresses through puberty, various radiographic parameters can be used to assess maturity. The most common method is assessment of bone age at the hand and wrist and development of the iliac apophysis (Risser sign), triradiate cartilage, olecranon apophysis ossification, and digital ossification.

The Risser sign is a measurement based on the ossification of the iliac apophysis, which is divided into four quadrants. The Risser sign proceeds from grade 0, no ossification, to grade 4, in which all four quadrants of the apophysis have ossification. Risser grade 5 is when the apophysis has fused completely to the ilium when the patient is skeletally mature. The Risser sign may not be as useful for predicting curve progression because of variations in the normal ossification patterns and because grade 1 has been found to begin after the period of rapid adolescent growth or PHV.

The PHV has been reported by several authors to be a better maturity indicator than the Risser sign, chronologic age, or menarchal age. PHV is calculated from serial height measurements and is expressed as centimeters of growth per year. Average values of PHV are 8 cm per year in girls and 9.5 cm per year in boys. Little et al., in a study of 120 girls with scoliosis, found that PHV reliably predicted cessation of growth (3.6 years after PHV in 90%) and likelihood of curve progression. Of 60 patients with curves of more than 30 degrees at PHV, 50 (83%) had curve progression to 45 degrees or more; of 28 with curves of 30 degrees or less at PHV, only one (4%) progressed to 45 degrees or more. Little et al. found similar results in boys with scoliosis and reported a 91% accuracy rate for predicting progression to 45 degrees or more. In both girls and boys, they found the PHV to be superior to the Risser sign, chronologic age, and menarchal age as a maturity indicator.

The triradiate cartilage begins to ossify in the early stages of puberty. In girls it is completely ossified after the period of PHV and before Risser grade 1 and menarche. In boys it is in the early stages of ossification when puberty begins. Sanders et al. found a higher rate of crankshaft phenomenon after posterior spinal fusion in patients at or before PHV as indicated by an open triradiate cartilage. These findings, however, may not be as common with modern pedicle screw fixation, which is more rigid and provides three-column fixation that may be more resistant to crankshaft than posterior hooks, which control only the posterior column of the spine ( Fig. 44.22 ).

FIGURE 44.22, Height velocity. Triradiate cartilage (TRC) closure occurs after period of peak height velocity (PHV) and before Risser grade 1 and menarche.

Other methods for evaluating maturity and the risk of curve progression are based on hand and wrist or elbow radiographs. The Sauvegrain method determines skeletal age from anteroposterior and lateral radiographs of the left elbow. It is a 27-point system based on four anatomic structures about the elbow: lateral condyle, trochlea, olecranon apophysis, and the proximal radial epiphysis. Skeletal age is determined from this score. Charles et al. reported a simple but reliable method to assess maturity based on the olecranon apophysis and allowed skeletal age to be determined at regular 6-month intervals from the age of 11 to 13 years in girls and from 13 to 15 years in boys. They found that this information complemented the Risser grade 0 and triradiate cartilage closure information ( Figs. 44.23 and 44.24 ).

FIGURE 44.23, Pubertal diagram divided into four zones. Zone 1, ascending side, triradiate cartilage open, bone age between 11 and 13 years in girls and boys (Risser 0). Zone 2, ascending side, triradiate cartilage closed, bone age between 11 and 13 years in girls and between 13 and 15 years in boys (Risser 0). Zone 3, descending side, elbow closed but greater trochanter not fused, bone age between 13 and 16 years in girls and between 15 and 18 years in boys (Risser 1 to 2). Zone 4, descending side, elbow closed and greater trochanter fused, bone age between 13 and 16 years in girls and between 15 and 18 years in boys (Risser 3 to 4).

FIGURE 44.24, Simplified skeletal age assessment with olecranon method during accelerating pubertal growth phase of peak height velocity and Risser grade 0 from ages of 11 to 13 years in girls and from 13 to 15 years in boys, with a decelerating growth phase after elbow fusion. Y-cartilage closure = triradiate cartilage closure.

Both the Tanner-Whitehouse-III Radius-Ulna-Short Bones (RUS) score, based on the radiographic appearance of the epiphyses of the distal radius, ulna, and small bones of the hands, and the digital skeletal age maturity scoring system, based on the metacarpals and phalanges, highly correlate with PHV and curve progression. However, these systems are cumbersome and not very practical to use in a busy clinical setting. Because of this, Sanders et al. reported a simplified classification based on the epiphyses of the phalanx, metacarpal, and distal radius. They were able to demonstrate that this method reliably predicted maturity and probability of progression to surgery (see Fig. 44.19 and Table 44.4 ).

TABLE 44.4

Logistic Projection of the Probability of Lenke Type 1 and Type 3 Curves Progressing to Surgery Assuming a Threshold of More Than 50 Degrees ^∗ ^, ^†

Reproduced from Sanders JO, Khoury JG, Kishan S, et al: Predicting scoliosis progression from skeletal maturity: a simplified classification during adolescence, J Bone Joint Surg 90A:540, 2008.

Curve (Degrees)	Stage 1	Stage 2	Stage 3	Stage 4	Stage 5	Stage 6	Stages 7 and 8
10	2% (0%-40%)	0% (0%-15%)	0% (0%-0%)	0% (0%-0%)	0% (0%-0%)	0% (0%-0%)	0% (0%-1%)
15	23% (4%-69%)	11% (1%-58%)	0% (0%-2%)	0% (0%-0%)	0% (0%-0%)	0% (0%-0%)	0% (0%-7%)
20	84% (40%-98%)	92% (56%-99%)	0% (0%-14%)	0% (0%-1%)	0% (0%-1%)	0% (0%-1%)	0% (0%-26%)
25	99% (68%-100%)	100% (92%-100%)	29% (3%-84%)	0% (0%-5%)	0% (0%-5%)	0% (0%-2%)	0% (0%-64%)
30	100% (83%-100%)	100% (98%-100%)	100% (47%-100%)	0% (0%-27%)	0% (0%-22%)	0% (0%-11%)	0% (0%-91%)
35	100% (91%-100%)	100% (100%-100%)	100% (89%-100%)	0% (0%-79%)	0% (0%-65%)	0% (0%-41%)	0% (0%-98%)
40	100% (95%-100%)	100% (100%-100%)	100% (98%-100%)	15% (0%-99%)	0% (0%-94%)	0% (0%-83%)	0% (0%-100%)
45	100% (98%-100%)	100% (100%-100%)	100% (100%-100%)	88% (2%-100%)	1% (0%-99%)	0% (0%-98%)	0% (0%-100%)

∗ Unshaded cells correspond with combinations of curve size and maturity stage for which surgery would be a plausible treatment if more than 50 degrees at maturity is accepted as the threshold for surgical treatment. Shaded cells correspond with combinations for which surgery would not be a plausible treatment.

† Cells with wide 95% confidence intervals (shown in parentheses) correspond with groups that had too few patients for accurate estimates (or groups that had no patients) and should be interpreted with caution.

Approximately 10% of patients with presumed adolescent idiopathic scoliosis have a neurologic abnormality. An MRI should be used when there is a concern for a neurologic etiology, such as a Chiari malformation, syringomyelia, or intraspinal tumor, for the scoliosis and is most commonly used when curves are left thoracic, rapidly progressing, or painful, or the physical examination is unreliable or concerning. Another valuable sign is lack of thoracic apical lordosis or hyperkyphosis.

Measurement of curves

The Cobb method of measurement recommended by the Terminology Committee of the SRS ( Fig. 44.25 ) consists of three steps: (1) locating the superior end vertebra, (2) locating the inferior end vertebra, and (3) drawing intersecting perpendicular lines from the superior surface of the superior end vertebra and from the inferior surface of the inferior end vertebra. The angle of deviation of these perpendicular lines from a straight line is the angle of the curve. If the endplates are obscured, the pedicles can be used instead. The end vertebra of the curve is the one that tilts the most into the concavity of the curve being measured. In general, on moving away from the apex of the curve, the next intervertebral space below the inferior end vertebra or above the superior end vertebra is wider on the concave side of the curve. Within the curve, the intervertebral spaces usually are wider on the convex side and narrower on the concave side. When significantly wedged, the vertebrae themselves, rather than the intervertebral disc spaces, may be wider on the convex side of the curve and narrower on the concave side. The reported interobserver and intraobserver variations in Cobb measurements average 5 to 7 degrees. The same levels should be measured between visits and variability should be taken into account in determining whether a curve is truly progressing.

FIGURE 44.25, Diagram of Cobb method (see text).

Vertebral rotation

Because of the three-dimensional nature of adolescent idiopathic scoliosis, accurate assessment of vertebral rotation both preoperatively and postoperatively is important. The two most commonly used methods of determining vertebral rotation from plain radiographs are those of Nash and Moe and of Perdriolle and Vidal. In the method of Nash and Moe, if the pedicles are equidistant from the sides of the vertebral bodies, no vertebral rotation is present (0 rotation). The grades progress to grade IV rotation, in which the pedicle is past the center of the vertebral body ( Fig. 44.26 ). It may be difficult to assess postoperative rotation because of the instrumentation obscuring the measurement landmarks. Kuklo et al. evaluated the utility of alternative radiographic measures of vertebral rotation. They found that the rib hump as measured on the lateral radiograph ( Fig. 44.27A ) and the apical vertebral body-rib ratio ( Fig. 44.27B ) showed a strong correlation with vertebral rotation and can be used when CT is not feasible or when instrumentation obscures the landmarks necessary for rotation to be evaluated by the other techniques. New slot digital scanning imaging techniques (EOS Imaging, Paris, France) provide fast and accurate three-dimensional reconstructions of the spine that can better determine vertebral body rotation without the radiation exposure from a CT scan.

FIGURE 44.27, A, Diagram of measurement technique for assessing rib hump (RH) deformity. RH is linear distance between left and right posterior rib prominences at apex of rib deformity on lateral radiograph. B, Diagram of measurement technique for apical vertebral body/rib ratio (AVB-R). AVB-R is ratio of linear measurements from lateral borders of apical thoracic vertebrae to chest wall on anteroposterior radiographs.

Sagittal balance

The importance of normal sagittal alignment has become recognized in the management of patients with spinal deformity. Sagittal alignment can be considered on a segmental (two vertebral bodies and intervening disc), regional (cervical, thoracic, thoracolumbar junction, lumbar, lumbosacral), or global basis. Global spinal alignment generally is considered to be an indication of overall sagittal balance.

Overall spinal sagittal balance is determined by a plumb line dropped from the dens, which should fall anterior to the thoracic spine, posterior to the lumbar spine, and through the posterior superior corner of S1 ( Fig. 44.28 ). Because the dens is difficult to evaluate on long scoliosis films, the plumb line usually is dropped from the middle of the C7 vertebral body. This plumb line is called the sagittal vertebral axis. A positive sagittal vertebral axis is considered present when the plumb line is anterior to the anterior aspect of S1. A negative sagittal vertebral axis occurs when this plumb line passes posterior to the anterior body of S1 ( Fig. 44.29 ). The overall sagittal balance is probably a more important measurement than regional and segmental measurements. In general, for sagittal balance to be maintained, lumbar lordosis should measure 20 to 30 degrees more than the kyphosis. If overall sagittal balance is not considered, correction to the normal range of lordosis without similar correction of the kyphotic thoracic spine can lead to significant sagittal imbalance ( Fig. 44.30 ).

FIGURE 44.28, C7 sagittal plumb line is useful measurement of sagittal balance. Plumb line dropped from middle of C7 vertebral body falls close to posterosuperior corner of S1 vertebral body.

FIGURE 44.29, Method of measurement of various parameters of sagittal spinal alignment. Sagittal vertical axis (SVA) is horizontal distance from C7 plumb line to front corner of sacrum. Positive values indicate position anterior to sacrum; negative values are through or behind sacrum. β, Angle of sacral inclination, is angle subtended by tangent to posterior border of S1 and vertical axis. δ, Cobb angle between two vertebrae.

FIGURE 44.30, A, Preoperative standing lateral radiograph in patient with neuromuscular scoliosis. B, Standing lateral view 1 month later indicates imbalance between kyphosis and lordosis correction with signs of early increasing thoracic kyphosis. C, Further follow-up of same patient shows increasing falling off of thoracic kyphosis above instrumentation.

In the thoracic spine, the normal sagittal curvature is kyphotic and typically is 30 to 40 degrees in adolescents. The kyphosis begins at the first thoracic vertebra and reaches its maximal segmental kyphosis at T6 or T7. Ranges of thoracic kyphosis in normal patients, both adults and children, have been reported. Although the kyphosis begins at T1, this vertebra often cannot be seen on standing long-cassette lateral films. The T4 or T5 vertebra is more easily seen and measured. Gelb et al. found that the upper thoracic kyphosis from T1 to T5 in 100 adults averaged 14 ± 8 degrees. Adding this number to the kyphosis measured from T5 to T12 provides a reasonable estimate of overall regional kyphosis.

The normal regional lumbar sagittal alignment is lordotic. The normal apex of this lordosis is at the vertebral body of L3 or L4 or the disc space itself. The segments at L4-L5 and L5-S1 account for 60% of the overall lumbar lordosis. It is important to remember that the lumbar discs account for 47 degrees of the lordosis (78%); the vertebral bodies themselves account for only12 degrees. This emphasizes the importance of preserving disc height during anterior procedures for the treatment of spinal deformities. Because 40% of the total lumbar lordosis is in the L5-S1 segment, it is important to be able to measure to the top of the sacrum, although this can be difficult on standing lateral images. The lumbar lordosis is a dependent variable based on the amount of kyphosis. For sagittal balance to be maintained, lordosis generally is 20 to 30 degrees larger than thoracic kyphosis.

The orientation of the sacrum, the sacral slope, and the pelvic incidence are closely associated with the characteristics of lumbar lordosis and location of the apex of lumbar lordosis ( Fig. 44.31 ). A sacral slope of less than 35 degrees and a low pelvic incidence are associated with a relatively flat, short lumbar lordosis. A sacral slope of more than 45 degrees and a high pelvic incidence are associated with a long, curved lumbar lordosis.

FIGURE 44.31, Sacral slope (SS) is angle subtended by horizontal reference line (HRL) and sacral endplate line (bc). SS shares common reference line (bc) with pelvic incidence (PI) and pelvic tilt (PT). PI is measured from static anatomic structures. PT and SS depend on angular position of sacrum/pelvis in relation to femoral heads, which changes with standing, sitting, and lying down. Relationship of PT and SS is affected by lumbosacropelvic flexion and extension. VRL , Vertical reference line.

The thoracolumbar junction is the transition area from a relatively rigid kyphotic thoracic spine to a relatively mobile lordotic lumbar spine. Bernhardt and Bridwell showed that the thoracolumbar junction is nearly straight. This relationship must be maintained during reconstructive procedures to prevent a junctional kyphosis.

Curve patterns

Idiopathic scoliosis curves were first descriptively classified by Ponseti and Friedman and later by King. These classification systems have been replaced by the Lenke classification, which uses the coronal and sagittal planes to help guide treatment decisions including fusion levels.

Lenke Classification

Measurements are obtained from standard posteroanterior, lateral, and right and left bending radiographs. The three steps in this classification system are (1) identification of the primary curve, (2) assignment of the lumbar modifier, and (3) assignment of the thoracic sagittal modifier. The first step is to identify the primary curve. These curves should be divided by region: proximal thoracic, main thoracic, and thoracolumbar or lumbar. Curves are considered to be structural curves if they are more than 25 degrees on posteroanterior radiographs and do not bend to less than 25 degrees on side-bending radiographs. Based on these measurements the curve can be classified into six types ( Fig. 44.32 ). The second step is to determine the lumbar spine modifier. This is determined by drawing a vertical line upward from the center of the sacrum (CSVL). The lumbar spine modifier is then determined by the relationship of the CSVL to the concave pedicle of the apical lumbar vertebra and can be assigned into A, B, or C. In type A, the CSVL is between the pedicles; in type B, it is between the medial pedicle wall and the lateral vertebra; and in type C, it is medial to the entire vertebra. The third step is to determine the thoracic sagittal modifier. The sagittal modifier is hypokyphotic (<10 degrees), normal (10 to 40 degrees), or hyperkyphotic (>40 degrees). Using this technique, fusion levels can be chosen so that the major and structural minor curves are included in the instrumentation and the nonstructural curves excluded. In addition, this classification allows better organization of similar curve patterns and provides comparisons of various treatment methods.

FIGURE 44.32, Curve types and criteria for structural curves and location of apex.

Nonoperative treatment

Various methods have been used to treat adolescent idiopathic scoliosis over the years, including physical therapy, manipulation, and electrical stimulation, but there is no scientific evidence supporting their effectiveness. The two most widely accepted nonoperative techniques for idiopathic scoliosis are observation and bracing, often in conjunction with Schroth-based physical therapy.

Observation

Because mild scoliosis is frequent in the general population and few individuals have curves that require treatment, no method is reliable for accurately predicting at the initial evaluation which curves will progress. For these reasons, observation, except in patients with large curves, should be the initial form of treatment. Attempts have been made to monitor external contours with measurement of the rib hump, measurement of the trunk rotation angle with a “scoliometer,” and use of contour devices such as surface topography scanning; however, these techniques have very limited, if any, clinical application. For this reason, radiographic evaluation remains the mainstay of observation. Because of intraobserver and interobserver variability in radiographic measurement, an increase of 5 or more degrees is considered progression. In general, the frequency of radiographic follow-up is driven by where the patient is in their development relative to their PHV ( Table 44.5 ).

Table 44.5

Suggested Follow-up Frequency for Adolescent Idiopathic Scoliosis

Age	Peak Height Velocity	Curve Magnitude	Frequency
Young	Before	<20 degrees	6 mo
Young	Before	>20 degrees	4 mo
Mid	In	All	4 mo
Older	After	<20 degrees	None
Older	After	>30 degrees	Annually to maturity ∗

∗ Should be followed every 5 years after skeletal maturity.

Curves of 30 to 40 degrees in skeletally mature patients generally do not require treatment, but because studies indicate a potential for progression in adult life, these patients should be observed with yearly standing posteroanterior radiographs for 2 to 3 years after skeletal maturity and then every 5 years.

Orthotic treatment

The goal of brace treatment is to limit further curve progression and avoid surgery. A small amount of correction may occur while in the brace, but the curve will generally settle to its pretreatment degree of curvature once the brace is discontinued. Brace correction of spinal curves is thought to occur through molding of the spine, trunk, and rib cage during growth, specifically through transverse loading of the spine through the use of corrective pads. The efficacy of brace treatment for patients with adolescent idiopathic scoliosis remains controversial. Numerous studies in the literature support the effectiveness of an orthosis in preventing curve progression and the need for surgical intervention. However, there are other studies that suggest bracing may not be effective. A large bracing study showed successful treatment in 72% of braced patients compared with 48% success with observation and concluded that bracing significantly decreased progression of high-risk curves to the threshold of surgery and that the benefit of bracing increased with longer hours of brace wear.

The SRS Committee on Bracing and Nonoperative Management has recommended standardization of criteria for adolescent idiopathic scoliosis brace studies so that valid and reliable comparisons can be made. The optimal inclusion criteria consist of age 10 years or older when a brace is prescribed, Risser grades 0 to 2, primary curve angles of 25 to 40 degrees, no prior treatment, and, if female, either premenarchal or less than 1 year postmenarchal. Bracing is recommended for a flexible curve of 25 degrees or more in a growing child with documented progression. Although surgery usually is indicated for curves in the 40- to 50-degree range in growing children, orthotic treatment may be considered for some curves in an effort to delay surgery to allow further maturation and spinal growth. Orthotic treatment is not used in patients with curves of more than 50 degrees.

Underarm braces (Boston, Wilmington, and Miami) have replaced the Milwaukee brace in most centers. However, these low-profile braces work best in patients whose curve apex is at T7 or lower. The Charleston and Providence nighttime bending braces hold the patient in maximal side-bending correction and are worn only at night for 8 to 10 hours. These braces are best suited for single thoracolumbar or lumbar curves.

The orthoses were originally intended to be worn 23 hours a day, but concern about compliance has led to part-time bracing regimens. Most part-time bracing protocols call for approximately 16 hours or less of brace wear each day. A meta-analysis of the literature found a relationship between the duration of brace wear per day and prevention of curve progression, suggesting that the more time that is spent in a brace, the less likely it will be for the curve to pro-gress. Another study found that the total number of hours of brace wear correlated with the lack of curve progression and inversely correlated with the need for surgical treatment. This effect was most significant in patients who were at Risser grade 0 or 1 or with an open triradiate cartilage at the beginning of treatment. Curves did not progress in 82% of patients who wore the brace more than 12 hours per day compared with only 31% of those who wore the brace less than 7 hours per day.

The SpineCor brace (Biorthex Inc., Boucherville, Quebec, Canada) is an adjustable, flexible, dynamic brace with the cited advantages of simplicity of use, comfort, increased mobility, high patient compliance, and effectiveness. Outcomes of clinical studies indicate that prevention of curve progression is better with the brace than with no treatment, but comparative studies have shown it to be less effective than rigid orthoses in preventing curve progression. It appears to provide the greatest benefit for children between the juvenile and early adolescent stages, generally between the ages of 6 and 11 years, with Cobb angles of less than 30 degrees in whom other forms of bracing have failed.

Operative treatment

Operative treatment is considered if the curve is likely to reach a magnitude that can be expected to become troublesome in adulthood. Although most authors recommend surgery when the curve reaches 50 degrees, other factors need to be considered. Smaller lumbar and thoracolumbar curves may cause significant trunk shift, coronal decompensation, and cosmetic deformity. Double 50-degree curves are not as cosmetically unacceptable as single curves, and if progression occurs in skeletally mature patients, it is likely to be gradual. In an immature patient, surgery may be considered for curves between 40 and 50 degrees, because of the high likelihood of growth-dependent progression. Surgery is more likely to be required in a patient with a curve that progresses despite brace treatment. Patients with significant back pain should have further evaluation before surgery for neurologic abnormalities. Thoracic lordosis also should be considered because it has a detrimental effect on pulmonary function, and bracing worsens thoracic lordosis. The general indications for operative treatment are summarized in Box 44.3 .

BOX 44.3

Indications for Operative Treatment of Idiopathic Scoliosis

▪
Increasing curve in growing child
▪
Severe deformity (>50 degrees) with asymmetry of trunk in adolescent
▪
Pain uncontrolled by nonoperative treatment
▪
Thoracic lordosis
▪
Significant cosmetic deformity

Preoperative preparation

Preoperative preparation is essential for an optimal surgical outcome. Aspirin-containing products or nonsteroidal antiinflammatory agents should be discontinued before surgery because these medications may increase surgical blood loss and oral contraceptives should be discontinued because of the risk of deep venous thrombosis postoperatively. Preoperative radiographic evaluation with posteroanterior, lateral, and side-bending films of the thoracic and lumbar spine are necessary to determine fusion levels. Advanced imaging, most commonly MRI but also CT and myelography, occasionally are needed to rule out conditions such as syringomyelia, diastematomyelia, and tethered cord.

Patients with adolescent idiopathic scoliosis should have preoperative pulmonary function studies if they have a history of poor exercise tolerance, a curve of more than 60 degrees associated with a history of reactive airway disease, or a curve of more than 80 degrees. Patients with larger thoracic curves, thoracic lordosis, and coronal imbalance may be at higher risk of pulmonary impairment, but some patients with smaller curves may have clinically relevant pulmonary impairment. In fact, in some patients the pulmonary impairment may be out of proportion to the severity of the scoliosis. In rare cases with very large curves, a tracheostomy should be considered with a vital capacity of less than 30% of predicted normal. Ideally this should be done preoperatively to allow healing and pulmonary optimization.

With advances in perioperative anesthetic techniques, such as the use of hypotensive anesthesia during surgical exposure and the use of antifibrinolytic agents, most commonly tranexamic acid, the need for transfusion following surgical treatment for scoliosis has decreased dramatically. The use of tranexamic acid has been shown in large multicenter studies, as well as randomized studies, to correlate with decreased blood loss, decreased cell-saver volume, and need for postoperative transfusion. In rare cases, preoperative autologous blood donations and/or preoperative erythropoietin can be used in patients who qualify to decrease the risk of homologous blood transfusions.

Intraoperative considerations

Because spinal surgery has the potential for significant blood loss, two large-bore intravenous lines are needed, and an arterial line is necessary for continuous blood pressure monitoring. An indwelling urinary catheter is used to monitor urinary output. Electrocardiographic leads, blood pressure cuff, and a pulse oximeter also are necessary.

Spinal cord monitoring using both spinal somatosensory-evoked potentials and motor-evoked potentials has become the standard of care during scoliosis surgery because it facilitates timely diagnosis of neurologic injury, allowing the surgeon time to correct the etiology before permanent neurologic harm occurs. A large series of surgically treated scoliosis patients found that the use of electrophysiology had a sensitivity of 100% and specificity of 87% and all events had an identifiable episode that led to the change.

Cervical and cortical leads to the surgical area can record stimulation of the distal sensory nerves and can alert the surgeon to possible alteration of spinal cord transmission. Preoperative monitoring for a “baseline” is helpful for comparison during the operative procedure. When somatosensory-evoked potentials are used, multiple recording sites must be used, including cortical, subcortical, and peripheral sites, and certain inhalation agents, such as halothane and isoflurane, should be avoided, as should diazepam and droperidol. The somatosensory-evoked potential is a useful adjunct for monitoring spinal cord function, but it is not infallible, and false-positive and false-negative results have been reported. An important limitation of the somatosensory-evoked potential is that it measures only the integrity of the sensory system.

The use of motor-evoked potentials will monitor the spinal cord motor tracts. The combination of motor-evoked potentials and somatosensory-evoked potentials can significantly decrease the chance of unrecognized injury to the spinal cord. Transcranial electrical stimulation of the motor cortex generates an electrical impulse that descends the corticospinal tract and enters the peripheral muscle, where this electrical impulse can be recorded. This allows monitoring of the ventral spinal cord, which is vulnerable to cord ischemia. For this reason, motor-evoked potentials are more sensitive to mean arterial pressure and hypotensive anesthesia, and changes in motor-evoked potentials occur more rapidly than in somatosensory-evoked potentials after a neurologic injury.

Triggered electromyographic monitoring is useful to detect a possible breach in the pedicle wall by a pedicle screw. A threshold of less than 6 mA should alert the surgeon to a possible breach.

The first available spinal cord monitoring technique was the Stagnara wake-up test, described by Vauzelle, Stagnara, and Jouvinroux in 1973. In this test, the anesthesia is decreased or reversed after correction of the spinal deformity. The patient is brought to a conscious level and asked to move both lower extremities. Once voluntary movement is noted, anesthesia is returned to the appropriate level and the surgical procedure is completed. With the widespread use of somatosensory and motor-evoked potentials, this technique is rarely used because of the risk of awaking a prone, intubated patient but is useful if concerns about the quality of the motor and somatosensory-evoked potentials exists or a spinal cord injury is suspected. The ankle clonus test has been reported as an alternative to the wake-up test. Clonus should be present for a brief period on emergence from anesthesia. The absence of clonus during this time is abnormal.

Hypotensive anesthesia, in which mean arterial blood pressure is kept at 65 mm Hg, is an effective way to decrease intraoperative blood loss. An arterial line is essential during this type of anesthesia. Care also must be taken in reducing blood pressure so that it does not lead to ischemia of the spinal cord. Hypotensive anesthesia should not be considered in patients with a heart condition or in patients with spinal cord compression in whom a decrease in arterial blood supply might restrict an already compromised spinal cord blood flow. Antifibrinolytics have been shown to reduce intraoperative blood loss, percent blood loss, and the need for postoperative transfusion, with the most commonly used being tranexamic acid. They are typically used in conjunction with other techniques such as hypotensive anesthesia, judicious use of crystalloids, and a cell saver to decrease surgical blood loss and rate of transfusion.

The cell saver is used in most institutions and has been shown to save approximately 50% of the red cell mass, thereby reducing the need for intraoperative blood transfusions. The cell saver is contraindicated in patients with malignant disease or infection. Care must be taken when using microfibrillar products such as Gelfoam and topical clotting agents such as thrombin to avoid direct aspiration of these, which can lead to microclot embolization. Thorough irrigation of the wound after the use of these products is recommended before resuming cell saver use. Certain substances such as antibiotics including bacitracin, as well as betadine and hydrogen peroxide, can cause red cell lysis. The surgeon should try to estimate preoperatively if enough blood will be salvaged to make the cell saver cost-effective.

Surgical goals

The goals of surgery for spinal deformity are to correct or improve the deformity, to maintain sagittal balance, to preserve or improve pulmonary function, to minimize morbidity or pain, to maximize postoperative function, and to improve or at least not to harm the function of the lumbar spine. To accomplish these goals in patients with idiopathic scoliosis, surgical techniques may include anterior, posterior, or combined anterior and posterior procedures. The surgical indications, techniques, and procedures are divided into anterior and posterior sections.

Posterior Surgeries for Idiopathic Scoliosis

The posterior approach to the spinal column is the most commonly used. It is familiar to all orthopaedic surgeons and offers a safe and extensile approach that exposes the entire vertebral column.

Technique 44.6

▪
Position the patient prone on a Jackson table (Mizuho OSI, Union City, CA) with the arms carefully supported and the elbows padded. The Jackson table eliminates intraabdominal pressure and helps reduce blood loss ( Fig. 44.33 ).
▪
Do not abduct the shoulders more than 90 degrees to prevent pressure or stretch on the brachial plexus.
▪
The Jackson table maintains the hips in extension, which will maintain the lumbar lordosis, which is extremely important in obtaining proper sagittal alignment of the spine with instrumentation. The knees are well padded and slightly flexed to relieve some pressure from the hamstring muscles.
▪
Carefully pad the pressure points. The upper pads of the frame should rest on the chest and not in the axilla to avoid pressure on any nerves from the brachial plexus.
▪
When the patient is positioned on the frame with the hips flexed, lumbar lordosis is partially eliminated. If the fusion is to be extended into the lower lumbar spine, elevate the knees and thighs so that the patient lies with the hip joints extended to maintain normal lumbar lordosis.
▪
Scrub the patient’s back with a surgical soap solution for 5 to 10 minutes and prepare the skin with an antiseptic solution. Drape the area of the operative site and use a plastic Steri-Drape (3M, St. Paul, MN) to seal off the skin.
▪
Make the skin incision in a straight line from one vertebra superior to the proposed fusion area to one vertebra inferior to it. A straight scar improves the postoperative appearance of the back ( Fig. 44.34A ). Make the initial incision through the dermal layer only. Infiltrate the intradermal and subcutaneous areas with an epinephrine solution (1:500,000).
▪
Deepen the incision to the level of the spinous processes and use self-retaining Weitlaner retractors to retract the skin margins. Control bleeding with an electrocautery. Identify the interspinous ligament between the spinous processes; this often appears as a white line. As the incision is deepened, keep the Weitlaner retractors tight to help with exposure and to minimize bleeding. Now incise the cartilaginous cap overlying the spinous processes as close to the midline as possible ( Fig. 44.34B ). This midline may vary because of rotation of the spinous processes.
▪
With use of a Cobb elevator and electrocautery, expose the spinous processes subperiosteally after the cartilaginous caps have been moved to either side.
▪
After several of the spinous processes have been exposed, move the Weitlaner retractors to a deeper level and maintain tension for retraction and hemostasis.
▪
After exposure of all spinous processes, a localizing radiograph can be obtained ( Fig. 44.35 ). Alternatively, the T12 rib and the L1 transverse process can be used to localize the levels. Continue the subperiosteal exposure of the entire area to be fused, keeping the retractors tight at all times ( Fig. 44.34C ). It is easier to dissect from caudad to cephalad because of the oblique attachments of the short rotator muscles and ligaments of the spine.
▪
Extend the subperiosteal dissection first to the facet joints on one side and then the other side, deepening the retractors as necessary. Continue the dissection laterally to the ends of the transverse processes on both sides.
▪
Coagulate the branch of the segmental vessel just lateral to each facet.
▪
Place the self-retaining retractors deeper to hold the entire incision open and exposed.
▪
Sponges soaked in the 1:500,000 epinephrine solution can be used to maintain hemostasis.
▪
Use a curet and pituitary rongeur to completely clean the interspinous ligaments and the facets of all ligamentous attachments and capsule, proceeding from the midline laterally ( Fig. 44.36 ) to decrease the possibility of the curet’s slipping and penetrating the spinal canal.
▪
The entire spine is now exposed from one transverse process to another, all soft tissue has been removed, and the spine is ready for instrumentation and arthrodesis as indicated by the procedure chosen.

Posterior arthrodesis

The long-term success of any operative procedure for scoliosis depends on a solid arthrodesis. The classic extraarticular Hibbs technique has been replaced by intraarticular fusion techniques that include the facet joints. The success of spinal arthrodesis depends on surgical preparation of the fusion site, systemic and local factors, ability of the graft material to stimulate a healing process, and biomechanical features of the graft positioning. To obtain the best field for the fusion, soft-tissue trauma should be minimal and avascular tissue should be removed from the graft bed. The surface of the bone and the facets should be decorticated to provide a large, maximally exposed surface area for vascular ingrowth and to allow delivery of more osteoprogenitor cells. The patient’s condition should be optimized through nutrition and control of associated medical problems. Smoking has been found to inhibit fusion significantly and should be discontinued before surgery.

While autogenous bone graft from the iliac crest remains the “gold standard” for graft material, combining osteogenic, osteoconductive, and osteoinductive properties, it rarely is used in routine adolescent idiopathic scoliosis surgery because of concerns about donor-site morbidity. Another excellent source of autogenous bone is rib obtained from a thoracoplasty. Allografts, which avoid donor site morbidity, are most commonly used, provide osteoconductive properties, and have been shown to produce results equal to those of autogenous iliac crest graft in young patients. Several alternative graft materials include tricalcium phosphate, hydroxyapatite, and demineralized bone matrix. Bone morphogenetic protein can supply osteoinductive properties but has not been routinely used in multilevel fusions required in adolescent patients.

With improvements in surgical techniques and the inclusion of intraarticular fusion, together with meticulous dissection around the transverse processes, the pseudarthrosis rate has been decreased to 2% or less in adolescents with idiopathic scoliosis.

Facet Fusion

Technique 44.7

(MOE)

▪
Expose the spine to the tips of the transverse processes as previously described (see Technique 44.6).
▪
Begin a cut over the cephalad articular processes at the base of the lamina and carry it along the transverse process almost to its tip. Bend this fragment laterally to lie between the transverse processes, leaving it hinged if possible.
▪
Thoroughly remove the cartilage from the superior articular process.
▪
Make another cut in the area of the superior articular facet with the Cobb gouge, beginning medially and working laterally to produce another hinged fragment. Alternatively, an ultrasonic bone scalpel (Misonix, Farmingdale, NY) can be used to decrease blood loss and the risk of spinal cord injury.
▪
Place cancellous bone graft in the defect created ( Fig. 44.37 ).
▪
In the lumbar spine, the facet joints are oriented in a more sagittal direction and a facet fusion is best accomplished by removal of the adjoining joint surface with a small osteotome or a needle-nose rongeur. This creates a defect that is packed with cancellous bone ( Fig. 44.38 ).
▪
Decorticate the entire exposed spine with Cobb gouges from the midline, progressing laterally so that if the gouge were to slip it would be moving away from the spinal canal. Alternatively, a high-speed burr can be used to decorticate the spine, decreasing the risk of spinal cord penetration.

Facet Fusion

Technique 44.8

(HALL)

▪
First, sharply cut the inferior facet with a gouge, remove this bone fragment to expose the superior facet cartilage, and remove this cartilage with a sharp curet. Alternatively, an ultrasonic bone scalpel (Misonix, Farmingdale, NY) can be used to decrease blood loss and the risk of spinal cord injury.
▪
Create a trough by removing the outer cortex of the superior facet and add cancellous bone grafts ( Fig. 44.39 ).
▪
Proceed with decortication as described in the Moe technique.

Bone grafting

Autogenous iliac crest bone graft has been considered the gold standard. The harvest of autogenous bone graft from the ilium adds to surgical time and can introduce the potential for intraoperative and postoperative morbidity associated with the procedure. With the use of modern-day rigid segmental instrumentation, the rate of pseudarthrosis with allograft is extremely low and equal to that with the use of autogenous graft. For these reasons, autogenous iliac crest bone graft is rarely if ever used in routine adolescent idiopathic scoliosis surgery. The time saved by using allograft in many cases offsets the additional cost. In rare revision settings or poor healing environments, the use of iliac crest autogenous graft can be helpful.

Autogenous Iliac Crest Bone Graft

Technique 44.9

▪
Make an incision over the iliac crest to be used ( Fig. 44.40A ). If the original incision extends far enough distally into the lumbar spine, the iliac crest can be exposed through the same incision by subcutaneous dissection.
▪
Infiltrate the intradermal and subcutaneous areas with 1:500,000 epinephrine solution.
▪
Expose the cartilaginous apophysis overlying the posterior iliac crest and split it in the middle.
▪
With a Cobb elevator, expose the ilium subperiosteally.
▪
The superior gluteal artery emerges from the area of the sciatic notch (see Fig. 44.40A ) and should be carefully avoided during the bone grafting procedure.
▪
If bicortical grafts are desired, expose the posterior crest of the ilium on the inner side and obtain two or three strips of bicortical graft with a large gouge. Otherwise, take cortical and cancellous strips from the outer table of the ilium ( Fig. 44.40B ).
▪
Place these bone grafts in a kidney basin and cover them with a sponge soaked in saline or blood.
▪
Control bleeding from the iliac crest with bone wax or Gelfoam.
▪
Approximate the cartilaginous cap of the posterior iliac crest with an absorbable stitch.
▪
Place a suction drain at the donor site and connect it to a separate reservoir to monitor postoperative bleeding here separately from the spinal fusion site.

Complications of bone grafting

The most common complication associated with bone graft harvesting from the posterior iliac crest is transient or permanent numbness over the skin of the buttock caused by injury of the superior cluneal nerves ( Fig. 44.41A ). The superior cluneal nerves supply sensation to a large area of the buttocks and pierce the lumbodorsal fascia and cross the posterior iliac crest beginning 8 cm lateral to the posterior superior iliac spine. A limited incision, staying within 8 cm of the posterior superior iliac spine, which will avoid the superior cluneal nerves, is recommended.

FIGURE 44.41, A, Superior cluneal nerve may be injured during harvest of bone graft from iliac crest. Limited incision (green line), staying within 8 cm of posterior superior iliac spine, avoids nerve. B, Posterior ligament complex provides most of stability of sacroiliac joint.

The superior gluteal artery exits the pelvis, enters the gluteal region through the superiormost portion of the sciatic notch, and sends extensive branches to the gluteal muscles. Care should be taken when a retractor is inserted into the sciatic notch. Injury to the superior gluteal artery will cause massive hemorrhage, and the artery generally retracts proximally into the pelvis. Control of the bleeding frequently requires bone removal from the sciatic notch to obtain sufficient exposure. It may be necessary to pack the wound, turn the patient, and have a general surgeon locate and ligate the hypogastric artery. Ureteral injury also can occur in the sciatic notch from the sharp tip of a retractor.

Most of the stability of the sacroiliac joint is provided by the posterior ligamentous complex ( Fig. 44.41B ). Injury to the sacroiliac joint from removal of these ligaments can range from clinical symptoms of instability to dislocation. Dislocation of the sacroiliac joint as a complication of full-thickness graft removal from the posterior ilium has been reported. If a full-thickness graft is obtained, it should not be obtained too close to the sacroiliac joint ( Fig. 44.42 ).

FIGURE 44.42, Axial view of sacroiliac joint. Full-thickness graft should not be obtained too close to sacroiliac joint to avoid damage to posterior ligamentous complex.

Posterior spinal instrumentation

The goals of instrumentation in scoliosis surgery are to correct the deformity as much as possible and to stabilize the spine in the corrected position while the fusion mass becomes solid. The fusion mass in a well-corrected spine is subjected to much lower bending moments and tensile forces than is the fusion mass in an uncorrected spine.

In 1962, Harrington introduced the first effective instrumentation system for scoliosis. For more than 30 years, use of the Harrington distraction rod, combined with a thorough posterior arthrodesis and immobilization in a cast or brace for 6 to 9 months, was the standard surgical treatment of adolescent idiopathic scoliosis. Despite its success, the Harrington instrumentation system had several disadvantages. Correction with this system is achieved with distraction, leading to loss of normal sagittal balance and creating a flatback deformity ( Fig. 44.43 ). Because this rod was anchored only at the ends of the construct, minimal rotational correction was obtained and anchor failure due to lamina failure was common. While transformative at its time, Harrington instrumentation has been replaced by more modern segmental instrumentation systems using multiple anchors, most commonly pedicle screws and hooks, which allow more powerful correction, rotational control, and better correction of sagittal plane deformity.

FIGURE 44.43, Effects of distraction rod in lumbar spine. If contouring for lordosis is inadequate, lumbar spine can be flattened by distracting force. Also note kyphotic deformity just superior to distraction rod.

Posterior segmental spinal instrumentation systems provide multiple points of fixation to the spine and apply compression, distraction, and rotation forces through the same rod. These systems generally do not require any postoperative immobilization. They provide better coronal plane correction and better control in the sagittal plane. Hypokyphosis in the thoracic spine can be reduced and lumbar lordosis preserved when the instrumentation extends to the lower lumbar spine. With the use of pedicle screws there appears to be better transverse plane correction (vertebral rotation). These systems generally have implant failure and pseudarthrosis rates lower than those of Harrington instrumentation ( ).

Three kinds of devices are available for fixation of posterior segmental instrumentation: pedicle screws, sublaminar wires/tapes, and hooks.

Correction maneuvers

A variety of techniques and maneuvers can be used to achieve correction of spinal deformity, and the specific technique used should be customized to each patient and his or her curve characteristics, making a thorough knowledge of each of these techniques essential. Correction of a scoliotic curve also can be obtained by translating the apex of the curve into a more normal position. Translation can be achieved by a rod derotation maneuver described by Cotrel and Dubousset; this is accomplished by connecting the precontoured concave rod to each fixation site and then rotating the rod approximately 90 degrees into the sagittal plane. This essentially converts the pre-existing scoliosis to kyphosis. This en bloc derotation maneuver results in a lateral translation of the apical vertebrae or an in situ relocation of the apex of the treated curve.

Pure translation is another method for correcting curves. This can be achieved with sublaminar wires or a reduction screw on the concave side. The rod is contoured into the desired amount of coronal and sagittal plane correction and placed into the proximal and distal fixation sites. The spine is then slowly and sequentially pulled to the precontoured rods using sublaminar wires or reduction screws.

In situ contouring is another correction technique. With the use of appropriate bending tools, in situ contouring in both the coronal and sagittal planes can improve spinal alignment in scoliosis. A cantilever technique can be used to reduce spinal deformity. With this technique the precontoured rod is inserted and fixed either proximally or distally and then sequentially reduced into each fixation site with a cantilever maneuver. This is usually followed by appropriate compression and distraction to finalize the correction. With the use of monoaxial and uniplanar pedicle screws, correction can be obtained by en bloc vertebral derotation over three or four apical vertebral segments or by direct segmental vertebral rotation in which the derotation maneuver is applied to individual vertebral segments.

Finally, distraction on the concave side of a thoracic curve will decrease scoliosis and thoracic kyphosis. Compression applied on the convex side of a lumbar curve will correct scoliosis and allow for restoration or maintenance of lumbar lordosis. Distraction and compression are the primary modes of correction when hooks are used due to their limited ability to rotate or translate the spine.

Segmental instrumentation: pedicle screws

Pedicle fixation

Pedicle screw fixation from the posterior approach into the vertebral body has become the most popular form of spinal fixation because of the ability to facilitate greater three-dimensional curve correction ( Fig. 44.44 ). While commonly used, there is still no evidence on the optimal number and placement of screws. Larson observed that early adopters of pedicle screw placement recommended higher screw densities, with two screws at every level. A recent expert consensus panel recommended an intermediate density (1.6 screws/level) with higher densities at the ends of the construct and at the apex. Several studies have shown no significant difference in curve correction between high- and low-density screw constructs. Because screw density correlates with intraoperative blood loss and surgical time, the screw density and the purpose of each screw in the construct should be carefully considered. In addition, implants make up 30% to 50% of the total surgical cost, so small changes in screw density can lead to cost savings that equal or exceed those of accelerated discharge pathways.

FIGURE 44.44, A and B, Preoperative anteroposterior and lateral radiographs of patient with idiopathic scoliosis treated with lumbar and thoracic pedicle screws. C and D, Postoperative posteroanterior and lateral radiographs.

In studies comparing hook fixation with thoracic pedicle screw fixation, thoracic posterior-only pedicle screw constructs were found to provide better correction than hook constructs. For each screw used there also is a risk of screw malposition. With a freehand technique, the rate of screw malposition is between 5% and 15%, which is experience dependent. The highest risk for malplacement is in the upper thoracic spine because of the smaller pedicle diameter at these levels. A recent meta-analysis comparing freehand to navigation-assisted pedicle screw techniques found the overall breach rate to be lower using navigation (7.9% vs. 9% to 17%); there were no screw-related complications in the navigation group, but there were 0 to 1.7% in the non-navigation group. The disadvantages of CT-based navigation are the cost, time, and radiation exposure. Newer techniques, such as the use of three-dimensional models, robotic-assisted drill hole placement, and patient-specific custom drill jigs, are under investigation. There is no consensus on the optimal treatment of a malplaced screw because most are asymptomatic; however, because of the potential for severe complications including aortic or esophageal erosion ( Fig. 44.45 ) and the relatively low risk of screw removal, a low threshold should exist for removal of malplaced screws.

FIGURE 44.45, A, Axial CT showing far lateral penetration and aortic impingement of thoracic pedicle screw. B, Sagittal reconstruction. Note aortic arch and heart.

A thorough knowledge of the pedicle anatomy is necessary for the use of pedicle fixation. The pedicle connects the posterior elements to the vertebral body. Medial to the pedicle are the epidural space, nerve root, and dural sac. The exiting nerve root at the level of the pedicle is close to the medial and caudal cortex of the pedicle ( Fig. 44.46 ). Close to the lateral and superior aspects of the pedicle cortex is the nerve root from the level above. At the L3 and L4 vertebral bodies, the common iliac artery and veins lie directly anterior to the pedicles ( Fig. 44.47 ). In the sacral region, the great vessels and their branches lie laterally along the sacral ala. In the midline of the sacrum, a variable middle sacral artery can lie directly anterior to the S1 vertebral body. Anterior penetration of a vertebral body can occur without being apparent on the radiograph unless a “near-approach” view is obtained ( Fig. 44.48 ).

FIGURE 44.46, A, and B, Pedicle screw placed too caudally causing nerve root impingement.

FIGURE 44.47, Vascular damage by insertion of screw beyond anterior cortex.

FIGURE 44.48, Near-approach radiographic view to decrease likelihood of anterior screw penetration. When drill (or screw or probe) tip is actually at anterior cortex, lateral view (0 degrees) misleadingly shows tip still to be some distance ( A ) away from cortex. When angle of view is too oblique (60 degrees), tip appears to be some distance ( B ) from cortex. Only when view is tangent to point of penetration (30 degrees in this illustration) does tip appear most nearly to approach actual breakthrough.

In a study of the size of pedicles in mature and immature spines, the transverse pedicle width at the L5 and L4 levels reached 8 mm or more in children 6 to 8 years of age, but transverse width at L3 approaching 8 mm was not seen until 9 to 11 years of age ( Fig. 44.49 ). The distance to the anterior cortex increased dramatically from the youngest age group until adulthood at all levels ( Fig. 44.50 ). In patients with spinal deformities, the pedicles, especially the concave pedicles, often are deformed, and care must be taken in insertion of any pedicle fixation.

FIGURE 44.49, Transverse pedicle isthmus widths.

FIGURE 44.50, Distance to anterior cortex through pedicle angle axis versus through line parallel to midline axis of vertebra.

Four anatomic types of pedicles exist ( Fig. 44.51 ): type A has a large cancellous channel in which the pedicle probe can be smoothly inserted without difficulty; type B has a small cancellous channel in which the probe fits snugly; type C is a cortical channel in which the probe must be tapped with a mallet to enter the body; and type D is an absent pedicle channel that requires a juxtapedicular screw position. Type A and B pedicles do not require special techniques for probe insertion, whereas type C and especially type D pedicles do require special methods. Pedicles located on the concave (compression) side of the curves were found to be significantly smaller than those on the convex side, regardless of whether they were cancellous or cortical. Of 1021 pedicles in which pedicle screws were placed, 61% were type A, 29.2% were type B, 6.8% were type C, and 3% were type D. CT validated the morphologic evaluation and description of the four pedicle types.

FIGURE 44.51, Pedicle channel classification (see text).

Various methods have been described for identifying the pedicle and placing the pedicle screw, but basic steps include (1) clearing the soft tissue, (2) exposing the cancellous bone of the pedicle canal by decortication at the intersection of the base of the facet and the middle of the transverse process, (3) probing the pedicle, (4) verifying the four walls of the pedicle canal by probing or obtaining radiographic confirmation, (5) tapping the pedicle, and (6) placing the screw.

In the lumbar spine, pedicle screws are commonly inserted with use of anatomic landmarks, and confirmatory radiographs are obtained. Because of the deformed pedicles associated with scoliosis, many surgeons use fluoroscopic guidance. Freehand pedicle screw placement in the thoracic spine, which reduces patient and surgeon radiographic exposure, may be safe in experienced hands and evidence suggests that lower medial breach rates are associated with surgeon experience. The technique significantly reduces exposure of both the surgeon and the patient to radiation. Because of the tight confines of the pedicle in the thoracic spine and the frequently altered normal anatomy, we still use fluoroscopy to identify the entry site into the thoracic pedicle and to confirm screw placement ( Figs 44.52 and 44.53 ). Frameless stereotactic technology allows three-dimensional navigation and is more commonly being used to guide and confirm pedicle screw placement. It has been shown to have a greater accuracy rate than other techniques but is associated with higher radiation exposure. It is important to have knowledge of and proficiency with multiple techniques to optimize the technique used based on the patient’s diagnosis and anatomy, as well as resources available.

FIGURE 44.52, Pedicle screw starting point shown on bone model. Note starting point is at lateral pedicle wall and centered in cranio-caudal axis.

FIGURE 44.53, Pedicle screw starting point using fluoroscopic assistance.

Insertion of lumbar pedicle screws

Zindrick described a “pedicle approach zone” ( Fig. 44.54 ) that is decorticated before the pedicle is cannulated with either a probe or pedicle awl. The awl is carefully advanced until resistance is felt. An intraoperative radiograph or C-arm image can be used to verify correct position. The pedicle awl should pass relatively easily and should not be forced into the pedicle. In addition to radiographs or image intensification, laminotomy and medial pedicle wall exposure can be done to help confirm the intrapedicular passage of the instrument. Once satisfactory entry into the pedicle has been achieved and palpation from within the pedicle finds solid bone margins along the pedicle wall throughout 360 degrees, the screw can be inserted. If the screws are self-tapping, the screw itself is inserted. If the screws require tapping, the tap is inserted first and then the screw. The common entry points in the lumbar spine are shown in Figure 44.55 . The position of the pedicle in the sacrum is shown in Figure 44.56 . In the lumbar spine, a medially directed screw allows the use of a longer screw and spares the facet joint, with less chance of injury to the common iliac vessels. Similarly, a medially directed sacral screw reduces the possibility of injury to anterior structures if the screw penetrates the anterior cortex.

FIGURE 44.54, A, Funnel-shaped pedicle approach zone in upper lumbar region (L1). B, Funnel-shaped pedicle approach zone in lower lumbar region (L5). With increased pedicle size, pedicle approach zone funnel increases, especially in lower lumbar spine, allowing more latitude in pedicle screw insertion than in smaller upper lumbar and thoracic pedicles.

FIGURE 44.55, Entrance points for pedicle screw placement in lumbar spine as described by Roy-Camille (X) and Weinstein (•). A, Lateral view. B, Posterior view. Weinstein approach reduces interference with upper uninvolved lumbar motion segment.

FIGURE 44.56, Coronal posterior view of contribution of sacrum and posterior element to pedicle approach zone.

When pedicle screws are used in the lumbar spine, screws usually are placed at every level on both the convex and concave sides. Each individual vertebra can be better derotated if it is instrumented on both sides (see deformity correction by direct vertebral rotation in Technique 44.10). In choosing the lowest instrumented vertebra, the standing posteroanterior films and the bending films must be considered. Bending films should be used in choosing the lowest instrumented lumbar vertebra. Instrumentation is stopped at the vertebra just above the first disc space that opens in the concavity of the lumbar curve on the bending film away from the concavity. Unless the curve is very flexible, the lower instrumented vertebra should at least touch the center sacral line on the standing posteroanterior radiograph.

Insertion of thoracic pedicle screws

The routine use of thoracic pedicle screws in adolescent idiopathic scoliosis has become more common. The advantages and disadvantages of thoracic screws are given in Box 44.4 .

BOX 44.4

Advantages and Disadvantages of Thoracic Pedicle Screws

Advantages

▪
When they are optimally placed, the screws are completely external to the spinal canal (supralaminar and infralaminar hooks, in contrast, are within the canal itself).
▪
Stronger fixation is possible than with hook implants.
▪
The screws are attached to all three columns, providing a rigid triangular crosslinked construct with a posterior-only implant.
▪
Facet joints, laminae, and transverse processes are free of implants; therefore, theoretically, there is more surface area for decortication.
▪
There is superior coronal correction and axial derotation.
▪
Most studies have shown slightly shorter fusion lengths than with hook constructs. With improved correction, there is a decreased need for anterior procedures and thoracoplasties.

Disadvantages

▪
The implants add significantly to the cost of the procedure.
▪
The potential complications in insertion of thoracic pedicle screws include injury to the spinal cord, nerve roots, pleural cavity, and aorta.
▪
Radiation exposure is significant to the surgeon and patient if routine fluoroscopy is used.

Thoracic Pedicle Screw Insertion Techniques

Technique 44.10

▪
Clean the facet joints of all capsular tissue. Perform a partial inferior articular process facetectomy to enhance fusion and to improve exposure of the entry site for the thoracic pedicle screws ( Fig. 44.57A ). Seeing the transverse processes, the lateral portion of the pars interarticularis, and the base of the superior articular process helps identify the starting points ( Fig. 44.58 ). In general, start the screw insertion from the neutrally rotated, most distal vertebra to be instrumented. Anatomic landmarks can be used as a guide for starting points and screw trajectory ( Fig. 44.57B ). Fixed-angle screws provide superior rotation in the thoracic spine and lumbar spine. Multiaxial screws can be used if needed.
▪
Perform a posterior cortical breach with a high-speed burr. A pedicle “blush” suggests entrance into the cancellous bone at the base of the pedicle, but this may not be seen in smaller pedicles because of the limited intrapedicular cancellous bone. Alternatively, screw starting points can be confirmed fluoroscopically ( Fig. 44.59 ).
▪
Use a thoracic gearshift probe to find the cancellous soft spot indicating entrance into the pedicle.
▪
Point the tip first laterally to avoid perforation of the medial cortex ( Fig. 44.57C ).
▪
Advance the tip 20 to 25 mm until the tip is anterior to (past) the spinal canal ( Fig. 44.57D ).
▪
Remove the gearshift probe to reorient it so that the tip points medially and then place the probe carefully back into the base of the prior hole and advance it to the desired depth ( Fig. 44.57E ). The average depth is 30 to 40 mm in the lower thoracic region, 20 to 30 mm in the midthoracic region, and 20 to 30 mm in the proximal thoracic region in adolescents.
▪
Rotate the probe in a 180-degree arc to ensure adequate room for the screw. Probing of the pedicle with the gearshift should proceed in a smooth and consistent manner with a snug feel. Any sudden advancement of the gearshift or loss of resistance suggests penetration into soft tissue and pedicle wall or vertebral body violation.
▪
Once the gearshift probe is removed, view the track to make sure that only blood is coming out and not cerebrospinal fluid.
▪
With use of a flexible ball-tipped probe, advance the feeler probe to the base (floor) of the hole to confirm five distinct bony borders: the floor and four walls (medial, lateral, superior, and inferior) ( Fig. 44.57F ). Take special care in feeling the walls to the first 10 to 15 mm of the track, as breaches here are at the depth of the spinal canal.
▪
If a soft-tissue breach is palpated, consider leaving the screw out. If it is a critical screw, redirect it. With the feeler probe at the base of the pedicle track, mark the length of the track with a hemostat and measure it ( Fig. 44.57G ).
▪
Undertap the pedicle track by 0.5 to 1 mm of the final screw diameter ( Fig. 44.57H ). After tapping, always palpate the tapped pedicle track again with the flexible feeler probe. This second palpation will allow identification of distinct bony ridges, confirming the intraosseous position of the track.
▪
Select the appropriate screw diameter and length by the preoperative radiographs, as well as by intraoperative measurement.
▪
Slowly advance the screw down the pedicle to ensure proper tracking while allowing viscoelastic expansion ( Fig. 44.57I-T ). This can be done safely using power or manual drivers.
▪
Confirm intraosseous screw placement.
▪
On the anteroposterior image intensification, make sure the screws are positioned correctly relative to each other. Screws should not go past the midline on the true anteroposterior image. For any screw that needs to be removed, re-probe the screw hole to ensure that there is no medial breach. Use the lateral image primarily to gauge the length of the screws. No screw should extend past the anterior border of the vertebral body.
▪
Use electromyographic stimulation with real-time monitoring of the appropriate thoracic nerve root, recording from the intercostal and/or rectus abdominis musculature. Below T12, the lumbar pedicle screws are tested by monitoring the appropriate lumbar nerve root. A triggered electromyographic threshold of less than 6 mA or a significant decrease from the average of all other screws may indicate a pedicle wall breach by the screw. If this is the case, remove the screw and palpate the pedicle wall before deciding whether to replace or to discard the screw.

See

Fusion levels and screw placement

The most widely used classification and guide for fusion levels is the Lenke classification. A review of this classification gave the following recommendations to aid in selecting fusion levels:

1.
All Lenke structural curves should be included in the fusion and instrumentation.
2.
The upper instrumented vertebra should not end at a kyphotic disc.
3.
T2 is selected as the upper instrumented vertebra when the left shoulder is elevated, T1 tilt is more than 5 degrees, and/or significant rotational prominences or trapezial fullness accompanies the proximal thoracic curve.
4.
In lumbar modifier A curves, the lower instrumented vertebra is the vertebra touching the center sacral vertebral line; however, the spine is fused one or two levels farther distal when L4 is tilted in the direction of the thoracic curve.

In lumbar modifier B and C curves, the thoracolumbar stable vertebra is selected as the lower instrumented vertebra.

The lower instrumented vertebra in lumbar structural curves is influenced by curve flexibility (proposed by the lower instrumented vertebra translation) and rotation and correction on bending radiographs.

Even with these guidelines and using Lenke’s classification, selection of fusion and instrumentation levels must be individualized for each patient .

Hook site preparation and placement

Before the widespread use of pedicle screw fixation, hook fixation was the most common method of spinal fixation. Hook fixation is still a useful technique in situations where pedicle screw fixation is not safe, possible, or available. There are basically three types of hooks: pedicle, transverse process, and laminar. The pedicle hooks are designed for secure fixation in the thoracic spine by insertion into the facet with impingement on the thoracic pedicle. Pedicle hooks are used in an upgoing direction at T10 or higher. The laminar hooks can be used in the thoracic and lumbar spine. These can be placed around either the superior or inferior edge of the lamina according to the desired direction and point of application of forces. Transverse process hooks typically are used at the cranial end of a construct to provide a “soft landing” or more flexible transition between the mobile spine cranially and the rigid instrumented spine caudally. These are placed around the superior aspect of the transverse process and can provide only compression and not distraction.

Pedicle Hook Implantation

Technique 44.11

▪
The pedicle hook is inserted in an upgoing direction from T1 to T10.
▪
The facet capsule is removed, and a portion of the inferior facet process is removed to facilitate insertion of the hook ( Fig. 44.60A ).
▪
After removal of the portion of the inferior facet process, use a curet to decorticate the facet joint.
▪
Introduce the pedicle finder into the facet joint and push gently against the pedicle ( Fig. 44.60B ). Take care in using this instrument that it is introduced into the intraarticular space and not into the bone of the inferior articular facet. It must find its way, sliding along the superior articular facet.
▪
Once the pedicle finder is in place, check the position by a laterally directed force applied to the finder. If the vertebra moves laterally when the pedicle finder is translated, the pedicle finder is in the correct place.
▪
Insert the pedicle hook with a hook inserter and holder if needed. Again, be certain that the horns of the bifid hook remain within the facet joint and do not hook into the remaining bone of the inferior facet ( Fig. 44.61 ).

Transverse Process Hook Implantation

Technique 44.12

▪
Prepare the area along the superior edge of the transverse process, using a transverse process elevator to separate the ligamentous attachment between the undersurface of the transverse process and the posterior arch of the rib medial to the rib transverse joint ( Fig. 44.62 ).
▪
With use of a transverse process hook holder, insert the hook around the superior edge of the transverse process.

LaminaR Hook Implantation

Technique 44.13

▪
Place laminar hooks around either the superior or inferior edge of the lamina, according to the desired direction of applied force. Carefully match the type of laminar hook to the shape of the lamina and obtain the closest possible fit to avoid the possibility of hook impingement on the spinal canal ( Fig. 44.63 ).
▪
To insert the supralaminar hook, remove the ligamentum flavum with Kerrison rongeurs and curets ( Fig. 44.64A ). In the lumbar area, enough room generally exists between the vertebrae to allow implantation of the hook without removal of bone. In the thoracic area, however, the spinous process of the superior vertebra must be removed first.
▪
After the canal is open, obtain lateral extension of the area by excising the medial portion of the inferior articular facet of the superior vertebra. This will allow sufficient room for insertion of the thoracic laminar hook.
▪
When the infralaminar hook is inserted, partially remove the ligamentum flavum or separate it from the inferior surface of the lamina. If necessary, remove a piece of the inferior border of the lamina to allow proper seating of the hook on the lamina ( Fig. 44.64B ). Take care to preserve the lateral wall of the inferior facet to avoid lateral dislodgment of the hook.
▪
When the inferiormost laminar hook is inserted, preserve the interspinous ligament and facet capsule to prevent kyphosis distal to the rods.

Sublaminar Wires

Sublaminar wires generally are not used alone as anchors at the upper or lower instrumented vertebrae because they provide no axial stability. They are useful, however, in and around the apex of curves to aid in the translation maneuver, in which the spine can be pulled to a precontoured rod, thus minimizing the need for derotational maneuvers. The more rigid the curve is, the more helpful these sublaminar wires or cables are ( Fig. 44.65 ). While sublaminar wires are simple and cost-effective, they have been replaced in many centers with sublaminar cables or tape because of increased safety, better load distribution, and the ability in some cases to attach directly to the rod and provide some measure of axial stability.

Technique 44.14

▪
Expose the spine as described in Technique 44.6.
▪
With a needle-nose rongeur, gradually thin the ligamentum flavum until the midline cleavage plane is visible. In the thoracic spine, the spinous processes slant distally and must be removed before the ligamentum flavum can be adequately seen ( Fig. 44.66 ). Once the midline cleavage is visible, carefully sweep a Penfield No. 4 dissector across the deep surface of the ligamentum flavum on the right and left sides ( Fig. 44.67 ). Use a Kerrison punch to remove the remainder of the ligamentum flavum ( Fig. 44.68 ). Take care during this step to avoid damaging the dura or epidural vessels.
▪
Johnston et al. showed that wire penetration into the neural canal during wire passage is substantial (up to 1 cm). Because the depth of penetration is less when a semicircular wire is used, shape the wire as shown in Figure 44.69 . The largest diameter of the bend should be slightly larger than the lamina. Always pass the wire in the midline and not laterally and remove the spinous processes before wire passage. It is important that both the surgeon and the assistant be completely prepared for each step before passage of the wire and that they are careful about sudden movements and inadvertent touching or hitting of the wires that have already been passed.
▪
Passing of the wire is divided into four steps: (1) introduction, (2) advancement, (3) roll-through, and (4) pull-through. Pass the more cephalad wires first and progress caudally.
▪
Gently place the tip of the wire into the neural canal at the inferior edge of the lamina in the midline. Hold the long end of the doubled wire in one hand and advance the tip with the other. Rest the hand that is advancing the tip firmly on the patient’s back. Lift the tails of the wire slightly, pulling them to keep the wire snugly against the undersurface of the lamina ( Fig. 44.70A ).
▪
Once the wire has been introduced, advance it 5 to 6 mm. Beginning roll-through too soon will cause the tip of the wire to strike the inferior portion of the vertebral arch, and the wire can be pushed more deeply into the neural canal ( Fig. 44.70B ).
▪
After advancement, roll the tip of the wire so that it emerges on the upper end of the lamina ( Fig. 44.70C ). As the tip of the wire emerges, use a nerve hook to pull the end farther up from the lamina to allow enough room for a needle holder, wire holder, or Kocher clamp to be placed into the loop of the wire by the assistant. Take the clamp from the assistant and pull the wire with the clamp until it is positioned beneath the lamina, with half its length protruding above and half below the lamina. As the clamp is pulled, gently feed the wire superiorly from the long end. This must be a coordinated maneuver and must be done by the surgeon.
▪
Once the wire has been pulled through, cut off the tip of the wire and place one length of the wire on the right side and the other length on the left side of the lamina.
▪
As an alternative, leave double wires on one side and pass another wire so that double wires are present on both sides.
▪
Crimp each wire into the surface of the lamina to prevent any wire from being pushed accidentally into the neural canal ( Fig. 44.71 ).
▪
As more wires are passed, it becomes more likely that the other wires will be accidentally hit, and care must be taken to prevent this.

FIGURE 44.65, A and B, Preoperative anteroposterior and lateral standing scoliosis films. Thoracolumbar curve measures 77 degrees. C and D, Postoperative correction by hooks with sublaminar cables, correcting thoracolumbar curve to 22 degrees. SEE TECHNIQUE 44.13.

Sublaminar Cables/Bands

The use of sublaminar cables or bands instead of monofilament stainless steel wire has become more popular because of wire breakage and migration, which have been serious complications of sublaminar wiring. The flexibility of sublaminar cables/bands, which are inserted in a similar fashion, prevents repeated contusions to the spinal cord that can occur during insertion of the rod and tightening of the wire. Sublaminar banding systems (OrthoPediatrics, Warsaw, IN) offer the advantage of a wider surface area for load sharing and the ability to directly connect to the rod providing some axial stability ( Fig. 44.72 ).

FIGURE 44.72, Polyester sublaminar tape with hook ( A ) that allows direct fixation to rod and axial control ( B ).

Instrumentation Sequence in Typical Lenke 1A Curve

The following is a typical instrumentation sequence for a Lenke 1A curve. Multiple systems are available to accomplish this, and readers are referred to the system-specific technique manual for further details of the system that best fits their practice.

Technique 44.15

▪
Place instrumentation at the appropriate levels based on the patient’s anatomy and the desired arthrodesis levels. At this point, cut the correction rod that will be placed on the concave side to the appropriate length, which generally is 2 to 3 cm longer than the overall cranial-to-caudal anchor length.
▪
Bend the rod to achieve correct sagittal plane contour. In some cases, a slight “over-bend” is helpful in restoring the sagittal plane from hypokyphosis to normal kyphosis. This is accomplished with small, incremental steps by use of the French bender. The use of pre-contoured rods can also be helpful.
▪
Place the contoured rod into the implants. This can be started from either the superior or inferior anchors. Place the set screws into the first hooks where the rod seats perfectly. After the rod is inserted into the first one or two anchors, it then becomes necessary to use one of several methods to facilitate rod reduction and fully seat the rod into the saddle of the implants.
▪
The “forceps rocker” method is effective for seating the rod into the implant when there is only a slight height difference between the rod and the implant saddle. To use the rocker, grasp the sides of the implant with a rocker cam above the rod and the forceps tips facing the same direction as the hook blade. Lever the rocker backward over the rod to seat the rod into the saddle of the implant. The set screw is then inserted into the hook.
▪
In situations in which the difference between the hook and rod is such that the rocker cannot be used, a rod reducer can be used. Slowly close the reducer by squeezing the handles together, allowing the attached sleeve to slide down and seat the rod into the saddle of the implant.
▪
Place a set screw through the set screw tube of the reducer, using the provisional driver.
▪
Once the contoured rod and all of the set screws have been placed, perform the rod rotation maneuver. Because of the corrective forces placed on the spine, a mean arterial pressure of at least 70 mm Hg is essential to maintain spinal cord perfusion. It also is helpful to obtain a baseline motor-evoked potential measurement before any reduction maneuver for comparison once the maneuvers have been performed. This is done slowly, and it is essential to watch all of the anchors because they can sometimes be dislodged during this rotational maneuver. The anchors at the curve apex are those most likely to back out during rod rotation. Using two rod holders, rotate the rod to translate the apex of the curve toward the midline. If the hooks begin to dislodge, place one of the rod grippers next to the hook and reseat the hook by use of a distractor. Once the rod rotation is complete, tighten the set screws.
▪
In situ benders are then used for correction and final adjustment of the rod in the sagittal plane. Bend the rod in small, incremental steps by use of the two bender tips positioned near each other on the rod.
▪
Once the contouring has been completed, if hook fixation has been used, perform distraction or compression to seat the hooks in their final positions. It is recommended to use a rod gripper as a stop for distraction maneuvers rather than any portion of the implant. Compression maneuvers generally are carried out on two hooks. Take care that these instruments are placed against the implant body and not against the set screw.
▪
Rod derotation maneuvers can now be performed if axial rotational correction is desired.
▪
After these maneuvers are complete, tighten the set screws further. Place the convex stabilizing rod, measure the length, and cut the rod to length. With use of the French bender, contour the rod according to the curvature of the spine in the residual position of alignment from the correction rod. Place the contoured rod into the hooks and provisionally secure the rods with set screws.
▪
Once the rod is secured to the implants, apply distraction and compression as necessary at the cranial and caudal ends of the construct to balance the spine and level the shoulders.
▪
Place the countertorque instrument over the implant and rod. Place the break-off driver through the cannulated countertorque.
▪
Perform decortication with either a power burr or Cobb gouge.
▪
Apply bone graft.
▪
Close the wound in the routine manner.

Postoperative Care

There has been considerable interest in accelerated discharge protocols using multimodal pain management with early feeding and Foley catheter and drain removal, as well as aggressive mobilization. Fletcher et al. published their results with an accelerated discharge pathway that was associated with a 31% decrease in hospital days (2.9 vs. 4.3), 33% decrease in hospital room charges, and 11% decrease in physical therapy costs. With modern rigid segmental instrumentation systems, patients are allowed to ambulate immediately after surgery, and bracing rarely is used. A recent consensus best practice guideline regarding postoperative management of adolescent idiopathic scoliosis patients made 19 recommendations for the postoperative management of patients following posterior spinal fusion for adolescent idiopathic scoliosis ( Fig. 44.73 ).

Deformity Correction By Direct Vertebral Rotation

Technique 44.16

▪
In this technique, bilateral pedicle screws are inserted at every level to be fused in the thoracic spine. The direct vertebral rotation is opposite to that of the vertebral rotation in the thoracic curve; apical and juxtaapical vertebrae are rotated clockwise for right thoracic curves in the transverse plane.
▪
Because of the corrective forces placed on the spine, a mean arterial pressure of at least 70 mm Hg is essential to maintain spinal cord perfusion. It is also helpful to obtain a baseline motor-evoked potential measurement before any reduction maneuver for comparison once the maneuvers have been completed.
▪
Insert screw derotators onto the pedicle screws of the juxtaapical vertebrae on both the concave and convex sides and derotate the vertebrae as much as possible. This can be done most commonly in an en bloc fashion with multiple levels rotated simultaneously or in some cases each level at a time ( Fig. 44.74 ).
▪
During rod derotation, push down on the convex screws and pull up on the concave screws simultaneously. An assistant should apply downward pressure on the convex apical ribs to aid in derotation as well.
▪
After completion of the derotation, lock the rod into position by tightening the set screws fully. This process can be repeated multiple times until the desired correction is obtained.
▪
If the curve is rigid, we have found that often little rod derotation is possible, and other techniques, such as rod bending, should be considered.

Complications and pitfalls in segmental instrumentation systems

In addition to the complications inherent in any spinal arthrodesis, segmental instrumentation systems have several potential pitfalls, most of which can be avoided by choosing the appropriate arthrodesis levels using criteria such as the Lenke classification, which helps determine which curve(s) to instrument and avoid ending instrumentation in the middle of a structural curve. One coronal plane problem that can occur is decompensation with selective fusion of the thoracic curve ( Fig. 44.75 ). If the curve is severely rotated clinically, it probably will need to be incorporated in the fusion. If a selective thoracic fusion is performed, the lower instrumented vertebra should at least touch the center sacral line on the standing posteroanterior preoperative radiograph.

FIGURE 44.75, Decompensated lumbar curve after fusion of thoracic curve only.

In addition, there has been considerable interest recently in sagittal plane abnormalities, most commonly hypokyphosis, in adolescent idiopathic scoliosis. With the use of rigid posterior fixation, it is important to avoid ending instrumentation at the apex of the sagittal plane abnormality, which can lead to a proximal or distal junctional kyphosis ( Fig. 44.76 ).

FIGURE 44.76, Proximal junctional kyphosis. Preoperative ( A ) and postoperative ( B ) images of 13-year-old girl who had posterior spinal fusion for adolescent idiopathic scoliosis. Postoperative proximal junctional kyphosis is +9 degrees, and the patient remains asymptomatic.

Another common strategic mistake is failure to recognize the significance of the upper thoracic curve preoperatively. If the upper thoracic curve does not correct on supine bending films to the predicted correction of the lower thoracic curve, elevation of the left shoulder and an unsightly deformity will occur ( Fig. 44.77 ). This mistake is prevented by carefully evaluating the clinical appearance of the shoulders and the bending films, as well as the standing radiographs, with special attention to this upper curve. Useful measurements from standing radiographs are the T1 tilt angle, the clavicle angle, and the radiographic shoulder height. The T1 tilt angle is measured by the intersection of a line drawn along the T1 cephalad endplate and a line parallel to the horizontal reference line ( Fig. 44.78 ). The clavicular angle is measured by the intersection of a line touching the two highest points of the clavicle and a line parallel to the horizontal reference line ( Fig. 44.79 ). The radiographic shoulder height is determined by the difference in the soft-tissue shadow directly superior to each acromioclavicular joint on a standing posteroanterior radiograph ( Fig. 44.80 ). A proximal thoracic curve should be considered structural if (1) the curve size is more than 30 degrees and remains more than 20 degrees on side-bending radiographs; (2) there is more than 1 cm of apical translation from the C7 plumb line; (3) there is a positive T1 tilt; and (4) clinical elevation of either shoulder (most commonly the left for right thoracic curves) is noted, depending on the curve type.

FIGURE 44.77, Elevation of shoulder caused by undercorrection of upper thoracic curve.

FIGURE 44.78, When right edge of vertebral body is up, tilt angle is defined as negative. When left edge of vertebral body is up, tilt angle is defined as positive.

FIGURE 44.79, Clavicular angle. CHRL , Clavicle horizontal reference line; CRL , clavicle reference line.

FIGURE 44.80, Radiographic shoulder height. IHRL , Inferior horizontal reference line; SHRL , superior horizontal reference line.

Management of rigid curves

Halo-Gravity Traction

Rigid curves of the spine in adolescents have historically been treated with halo traction as an adjunct to surgery. This allows gradual correction of up to 35% of large spinal deformities and allows preoperative nutritional and pulmonary optimization. Often, posterior releases and instrumentation can be done at the time of halo placement to improve correction in traction. Gradual weight progression to 30% to 50% of the patient’s body weight is recommended, with at least daily neurologic assessments including the cranial nerves. Most commonly, hospitalization is required for this, with most correction being obtained in 3 to 4 weeks ( Fig. 44.81 ).

Technique 44.17

(SPONSELLER AND TAKENAGA)

▪
Sedation and local anesthesia should be used for this procedure.
▪
Place the halo just below the equator of the skull, above the eyebrows and pinnae of the ears.
▪
Six to eight pins are used in children younger than 6 years of age and tightened to 4 in-lb of torque. In older children or adults (if there is normal bone density), the pins are tightened to 8 in-lb. Place the anterior pins lateral to the midportion of the eyebrows to avoid the supraorbital nerves and ensure that the patient’s eyes will close after pin placement. Place the posterior pins diametrically opposite the anterior pins. Retighten the pins after 24 to 48 hours. If there is loosening after this, the pin should be relocated.
▪
Begin traction immediately with 5 lb of weight for young children and 10 lb for children close to maturity.
▪
Gradually increase the traction weight by 2 to 3 lb/day as tolerated, with the goal being a weight of 33% to 50% of the patient’s body weight. Incline the bed downward caudally.
▪
Inspect the patient’s skin regularly because pressure sores from bony prominences are common, especially in patients who have trouble turning themselves.
▪
Continue traction throughout the day. Patients should be upright in a halo wheelchair or walker for part of the day. The goal is to suspend the patient’s trunk as much as possible. Traction also can be applied when the patient is standing in a specially designed walker. Decrease the traction weight when the patient is sleeping, especially when the weight is near its maximum.
▪
Check the patient’s neurologic status including cranial nerve function in the upper and lower extremities. If changes occur, immediately decrease or remove the weight and reassess the patient.
▪
The duration of preoperative halo-gravity traction may range from 2 to 12 weeks depending on the severity of the curve, its response to traction, and the overall condition of the patient.
▪
Obtain radiographs approximately every week to assess the improvement obtained.
▪
Longer periods of traction may help to optimize nutrition and minimize pulmonary problems in those with borderline pulmonary or nutritional reserve.

FIGURE 44.81, Child in halo-gravity traction. SEE TECHNIQUE 44.17.

Temporary Distraction Rod

The use of temporary internal distraction rods in advance of the corrective surgical procedure has been described as an alternative to halo traction for severe rigid curves. Improved curve correction and restoration of sagittal and coronal contours have been cited as advantages to this technique. Placement of one or two temporary rods, soft-tissue releases, and osteotomies are performed usually 1 week before the permanent final implants are placed and fusion performed. The time between procedures can be longer than 1 week if necessary.

Before surgery, standard anteroposterior and lateral plain radiographs of the spine should be obtained with the patient standing or sitting, depending on the neurologic status. Traction films are helpful in predicting the amount of correction that can be obtained with a temporary rod. In addition, MRI and CT of the cervical, thoracic, and lumbar spine should be obtained to evaluate the precise spinal anatomy. Preoperative antibiotics should be administered.

Technique 44.18

(BUCHOWSKI ET AL.)

▪
Position the patient on a Jackson table in routine fashion; Gardner-Wells tongs can be helpful to provide additional traction. The goal when positioning the patient on the table is to obtain as much correction of body alignment as possible to lessen the force required to achieve intraoperative correction, and neuromonitoring is essential because a distraction force will be placed on the spine.
▪
Place pedicle screws in a standard fashion in the one or two vertebral bodies that are not intended to be the final cephalad fixation due to loosening that may occur. Alternatively, spinal hooks or ribs can be used as temporary cephalad anchor points.
▪
For placement of the caudal anchors, use standard lumbar pedicle screws, placing two screws (or more, depending on bone quality) at adjacent vertebrae. Alternatively, sublaminar hooks can be used. Again, the vertebrae cephalad to the end vertebrae of the final construct should be chosen because some loosening of the temporary anchor points is expected to occur with distraction.
▪
If the pelvis is used for anchoring points, expose the iliac spine. Place an iliac screw in the posterior superior iliac crest close to (but not entering) the sciatic notch. It should be placed parallel and at least 2 cm lateral to where the permanent iliac screw will be placed. Alternatively, an S-shaped hook may be used, and this may be easier to connect to the distraction rod with a side-to-side connector.
▪
Although there are several possibilities for placement of internal distraction rod constructs ( Fig. 44.82A-C ), the simplest is to attach one distraction rod to the cephalad anchor points and a second rod to the caudal anchor points, connecting them in a side-to-side connector with overlap of the rods ( Fig. 44.82B ). In some patients with extreme deformity, it may be necessary to attach two short rods (one attached cephalad and one caudal) to a third distraction rod using multiaxial crosslink connectors ( Fig. 44.82A ).
▪
Apply distraction across these two rods serially by loosening and tightening the side-to-side connector. Careful attention should be given to spinal cord function during the distraction process. If a depression in the spinal cord signal is noticed, the amount of correction should be decreased and a wake-up test performed.
▪
Once the temporary rod or rods have been placed, expose the rest of the spine subperiosteally. Perform releases and osteotomies as necessary to allow additional correction of the spine. Although technically more difficult, additional anchor points can be placed after releases and osteotomies if necessary.
▪
Small amounts of distraction should be performed throughout the procedure to allow maximal correction with minimal stress. With time, soft-tissue release, facetectomies, and osteotomies, additional correction can be obtained with the goal at the end of surgery to have correction greater than that shown on the supine traction film with 50% or more correction in the Cobb angle. Bone graft is not used at this time but can be stored in a paraspinal muscle pouch for the final procedure.
▪
Closure may be difficult because substantial soft-tissue lengthening occurs with distraction and the rods usually are lateral to the transverse processes. If necessary, raise thick local flaps including the paraspinal muscles to make closure possible. Use closed suction drains in the space created during the closure.

Stage II Definitive Surgery

▪
Reexpose the spine. Leaving the temporary rod(s) in place if feasible, create the anchor points for the final construct. There should be a substantial increase in the ability to cor rect the spine at this point, and it may be possible to gain additional distraction.
▪
Remove the temporary instrumentation and insert the final implants.
▪
Perform repeat pulsed irrigation and drainage and close the wound.

Postoperative Care

Between the first and second stages, parenteral nutrition is recommended until the patient can optimize oral intake. Sitting, standing, and walking are encouraged to avoid pulmonary complications. Casting or bracing is not required.

Anterior Release

Complete anterior release of the thoracic or lumbar spine, or both, allows improved mobilization of a curve and correction of deformity; however, the benefits of this must be weighed against increased surgical time and potential complications. Anterior release can be done through an open thoracotomy, thoracoscopically, or in conjunction with anterior instrumentation. With the increased correction seen with posterior instrumentation systems, the use of anterior release alone continues to decrease. It is still useful in patients with large and/or stiff deformities.

Technique 44.19

(LETKO ET AL.)

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In the thoracic spine, resect the convex rib heads and attempt to rupture the concave costovertebral joints.
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In both the thoracic and lumbar spine, remove the disc and posterior annulus. Release the posterior longitudinal ligament.
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Resect the convex inferior endplate with or without resection of the convex superior endplate to allow mobilization and correction in the coronal plane. By shortening the anterior column, hypokyphosis in the thoracic sagittal profile can be corrected to normal.
▪
Anterior structural support of the lumbar spine and thoracolumbar junction is recommended to prevent kyphosis.
▪
After complete anterior release, anterior instrumentation can be performed if the curve is not too rigid or large.

Osteotomy In Complex Spinal Deformity

Spinal osteotomy should be considered for patients with large, stiff curves for whom instrumentation alone cannot correct the deformity or restore balance. The Smith-Petersen and Ponte osteotomies are the most straightforward, with the Ponte osteotomy being the most used dorsal column shortening osteotomy. The difference between the Smith-Petersen osteotomy and the Ponte osteotomy is that, while both shorten the dorsal column, the Smith-Petersen osteotomy opens the anterior column, placing stretch on the great vessels, where the Ponte osteotomy does not. The classic indication for Ponte osteotomies, which allows the posterior column of the spine to shorten, was a long rounded kyphosis as in Scheuermann kyphosis; however, it is a versatile procedure that can be performed safely to aid in the gradual correction of rigid scoliotic curves. If soft-tissue releases are insufficient in obtaining correction, proceeding to osteotomy is the next step. The Ponte osteotomy is performed for scoliosis of more than 70 to 75 degrees that does not bend down to less than 40 degrees or for kyphosis that corrects to greater than 40 to 50 degrees in hyperextension. The use of Ponte osteotomies in patients with adolescent idiopathic scoliosis is associated with high rates of blood loss and neuromonitoring events. A multicenter study of 2210 patients found the rate of neurologic complications (0.37% vs. 0.17%) and neuromonitoring events (7.6% vs. 4.2%) were higher in patients who had Ponte osteotomies compared to those who did not. The cause of this is multifactorial but should be kept in mind when considering the use of Ponte osteotomies. In general, 1 mm of resection equals 1 degree of correction, with a possible correction of 5 to 10 degrees per level. Multiple levels can be resected to obtain more correction. A collapsed or immobile disc may be a contraindication to this technique. The choice of osteotomy depends on the apex of the deformity.

Technique 44.20 Figure 44.83

(PONTE OSTEOTOMY)

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After exposing the spine as described in Technique 44.6, perform complete facetectomies for complete exposure.
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Develop the screw tracks for subsequent pedicle screw placement (without placing the screws) to help guide the osteotomy.
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Remove the lamina, ligamentum flavum, and superior and inferior articular processes bilaterally, and resect the spinous process of the vertebra just cephalad to the osteotomy site.
▪
Create a wedge-shaped osteotomy 7 to 10 mm in width and carry it laterally to the intervertebral notch with small Kerrison rongeurs. An ultrasound bone scalpel, which provides excellent hemostasis and safety, can also be used. The point should be oriented distally. Both limbs of the wedge should be symmetric unless some coronal plane correction is desired. Take care to avoid the pedicles above and below the osteotomy and the nerve roots. If there is significant rotational deformity, open the osteotomy to a larger degree on the convex side.
▪
Remove the more superior facet to help prevent impingement of the superior nerve root.
▪
At this point, instrumentation can be added as indicated to achieve necessary correction.

FIGURE 44.83, Ponte osteotomies for correction of kyphosis. A and B, Wedge-shaped osteotomies. C and D, Placement of rod for correction. SEE TECHNIQUE 44.20.

Posterior Thoracic Vertebral Column Resection

Vertebral column resection is indicated for patients with complex, rigid, spinal deformities that cannot be corrected by less aggressive osteotomies. Circumferential access is provided to the vertebral column and neural elements for decompression and stabilization. This procedure is quite challenging and should be done by surgeons with specialized training and experience. It entails resection of one or more entire vertebral segments, including the posterior elements, vertebral body, and adjacent discs. Patients with cardiopulmonary comorbidities may not be suitable candidates.

Technique 44.21

(POWERS ET AL.)

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Position the patient on a Jackson table with adjustable pads. Intraoperative halo-gravity traction can be used. Neuromonitoring is essential for this procedure.
▪
Subperiosteally expose the spine out to the tips of the transverse process ( Fig. 44.84A ).
▪
Place pedicle screws using a freehand technique at the preplanned levels of fusion, a minimum of three levels above and three below the vertebral column resection ( Fig. 44.84C ). The spine is considered unstable from the time resection begins until final correction is achieved. A minimum of six points of fixation, both cephalad and caudal to the resection, is recommended. Multiaxial reduction screws can be placed at the apical concave regions of severe scoliosis or at the proximal or distal regions of severe kyphoscoliosis or kyphosis. In the lumbar spine, they should be placed in the concavity of the lumbar region.
▪
Expose 4 to 5 cm of the medial ribs corresponding with the level of resection. Remove the ribs by cutting each laterally and then disarticulating the costovertebral joints, or resect the transverse process at the level of the resection bilaterally to weaken the attachment of the rib head. The removal of the ribs and transverse process allows access to the lateral pedicle wall and vertebral body and can be used as a graft to fill the laminectomy defect later.
▪
After bilateral costotransversectomy, dissect the vertebral body wall anteriorly until the anterior vertebral body is exposed. Protect the thoracic sympathetic chain, anterior and posterior vessels, and pleura with a retractor.
▪
Perform bilateral laminectomies and facetectomies at the levels to be resected and complete the posterior decompression by removing the lamina cephalad to the pedicles above the resection and caudal to the pedicles below the resection ( Fig. 44.85A ). Posterior column exposure should be 5 to 6 cm to allow access to the spinal cord and to prevent dural buckling or impingement. Ligate the corresponding nerve roots medial and dorsal to the root ganglion.
▪
Once the osteotomies are complete, insert a temporary stabilizing rod and fix with two or three pedicle screws above and below the vertebral column resection ( Fig. 44.85B,C ). Depending on the deformity, one or two rods can be used to prevent subluxation of the spine.
▪
Identify the pedicles to be resected and enter through their lateral wall to gain access to the vertebral body. Complete the corpectomy by curetting the cancellous bone out of the vertebral body. Save this bone for later bone grafting. Most of the vertebral body removed should be from the convexity of the deformity. Powers preferred to perform resection from the concave side before the convex side removal to minimize bleeding and to remove some tension from the concave side before proceeding. Except for the anterior shell, remove the entire vertebral body. Keep a thin rim of bone intact on the anterior longitudinal ligament for fusion. Thin the anterior bone if it is thick and cortical.
▪
Perform discectomies above and below the resected body to expose the adjacent vertebral body endplates; however, avoid violating these because this can lead to interbody cage subsidence ( Fig. 44.86 ).
▪
For removal of the posterior wall, inspect the dura and free it of any attachments, such as the anterior epidural venous plexus, the posterior longitudinal ligament, or osteophytes. Control epidural bleeding, which can be significant, with bipolar electrocautery. Once the dura is freed, the thin posterior vertebral body can be tamped away from the spinal cord into the corpectomy defect ( Fig. 44.87A ). Inspect the dura after posterior vertebral body removal and remove any points of attachment or compression.
▪
Once the resection is complete, closure of the defect and deformity correction are performed. In this procedure, the spinal column is always shortened, not lengthened, with compression. Obtain correction with pedicle screws or using a construct-to-construct closure method performed by placing a construct rod above and one below to distribute forces of correction over several pedicle screw levels. Compression should proceed slowly because subluxation or dural impingement may occur ( Fig. 44.87B ).
▪
In any deformity with a degree of kyphosis, Powers et al. recommend using an anterior structural cage to prevent overshortening and to help provide extra kyphosis correction.
▪
Once the vertebral column resection has been completed, place a permanent contralateral rod and remove the temporary rod. Then place a second permanent rod on the ipsilateral side and perform appropriate correction compression or distraction maneuvers as necessary.
▪
Confirm alignment by intraoperative radiographs ( Fig. 44.88 ) and perform a final circumferential dural inspection.
▪
Place split-thickness rib autograft over the laminectomy defect and secure it to the rods using sutures or a crosslink.
▪
Irrigate the wound with saline. Decorticate the posterior spine and facet joints with a high-speed burr and place copious amounts of bone graft.
▪
Place subfascial and suprafascial Hemovac drains through separate stab incisions and close the wound in layers with interrupted absorbable sutures.

Postoperative Care

The suction drain is removed once the drainage is less than 50 mL per 8-hour shift or at 48 hours postoperatively. Most patients will develop a postoperative ileus. Food or liquids are begun slowly and advanced as tolerated. Most patients also develop a postoperative atelectasis and temperature elevation. This is managed with routine “pulmonary toilet” and incentive spirometer. Intravenous antibiotics are administered for 24 hours. If the patient is old enough, a patient-controlled pain medication pump is used. Postoperative continuous epidural analgesia using local anesthetic agents or opioids, or both, can be used in appropriate situations. The patient is gradually gotten out of bed as allowed by pain tolerance. A postoperative brace or no immobilization may be used depending on the stability of the instrumentation construct. When the temperature has subsided and the patient is relatively independently ambulatory and tolerating food and liquid intake, the patient is discharged. At the 6-month checkup, if the fusion appears solid, most limitations are lifted. We generally advise against contact sports after this type of spinal surgery.

Complications of posterior scoliosis surgery

Early complications

The Scoliosis Research Society morbidity and mortality database showed that for scoliosis surgery the overall complication rate was 10%, with a 0.7% new neurologic deficit rate for pedicle screw instrumentation and a 0.02% mortality rate for idiopathic scoliosis. A review of 2005 patients from the National Surgical Quality Improvement Program (NSQIP) database found a 10% complication rate at 30 days, which was higher in neuromuscular patients than in adolescent idiopathic scoliosis patients. Risk factors for readmission include cognitive delays, increased ASA class, and longer surgical time. The frequency of 2-year unplanned return to surgery for modern pedicle screw constructs is 3.5%, which increases to 7.5% at 5 years. The most common causes of reoperation include infection, symptomatic implants, and misplaced pedicle screws.

Neurologic Injury

The most feared and unpredictable complication in scoliosis surgery remains neurologic injury. For patients undergoing spinal fusion for adolescent idiopathic scoliosis, the incidence of neurologic injury is relatively low, between 0.32% and 0.69%. Causative factors include unrecognized spinal cord tethers, ischemia secondary to spinal cord stretch, and direct injury from surgical instruments, often combined with intraoperative hypotension. Ponte osteotomies have been associated with increased rates of neuromonitoring alerts.

Management of an intraoperative neurologic deficit begins with a series of corrective actions that should be planned for by the surgical team, including nursing and anesthesia personnel, well in advance of the event. A recent expert consensus-based best practice guideline for neuromonitoring changes has been published ( Fig. 44.89 ) and should be placed on the wall of the operating room and followed if neurologic changes occur. (Spinal cord monitoring and the wake-up test are discussed in the section on intraoperative considerations for operative treatment of adolescent idiopathic scoliosis.)

FIGURE 44.89, Checklist for the response to intraoperative neuromonitoring changes in patients with a stable spine.

Infection

Perioperative wound infection is the most common cause of readmission for adolescent idiopathic surgical patients, with a rate of approximately 1%, although there is variability between centers. The rarity of postoperative infections in adolescent idiopathic scoliosis patients makes randomized clinical trials difficult, if not impossible. Best practice guidelines from high-risk patients, including neuromuscular and early-onset scoliosis patients, can be extrapolated to adolescent idiopathic patients. In neuromuscular patients, the most important factor was timely dosing of antibiotics within 1 hour of the start of the procedure. The use of vancomycin powder and dilute betadine irrigation at the end of the procedure were also believed to be helpful. A recent multicenter report found that obesity was the only factor that predicted a sevenfold increased infection rate in adolescent idiopathic scoliosis patients in high-volume centers.

There are two types of infections: immediate perioperative and delayed. The first is obvious because a high fever develops, usually within 2 to 5 days after surgery, and the wound almost always appears infected. In the second type, the temperature is elevated only slightly or moderately and the wound appears relatively normal. Diagnosis of this latter type of wound infection may be difficult. Patients often have postoperative temperature elevation of up to 102°F, which should decline gradually during the first 4 postoperative days. Any spike of temperature above 102°F should strongly suggest a deep wound infection, especially if the patient’s general condition does not steadily improve. The appearance of the wound can be deceiving, with no significant erythema or tenderness. Prompt aspiration of the wound in several sites is recommended. Urgent thorough irrigation and debridement with retention of implants, if possible, should be performed in conjunction with consultation with infectious disease experts for long-term antibiotic therapy. A recent multicenter review found that with aggressive treatment, patients with early postoperative infections can retain their implants 76% of the time. Delayed wound infections (>6 months after index procedure) are more common than acute deep wound infections and usually are caused by indolent skin flora organisms such as Propionibacterium acnes or Staphylococcus epidermidis. The rate of late infection may be decreasing due to the fact that the risk of delayed infection is higher with stainless steel implants than with other metals now in use. In these infections, implant removal usually is necessary to eradicate the infection.

Ileus

Ileus is a common complication after both anterior and posterior spinal fusion. Oral feedings are resumed slowly after surgery. A multimodal approach to decreasing the rate of gastrointestinal complications, including early mobilization, decreased narcotic usage, epidural catheters, and early feeding, have been helpful. Malnutrition is uncommon in teenagers with idiopathic scoliosis, but patients requiring a two-stage corrective procedure may become malnourished as a result of the limited oral calorie intake and increased caloric requirements associated with closely spaced surgical procedures, and nutritional consultation and supplementation including parenteral nutrition should be considered.

Superior Mesenteric Artery Syndrome

Superior mesenteric artery syndrome can present 1 to 2 weeks after surgery as abdominal pain and distention and vomiting. It is due to compression of the duodenum between the superior mesenteric artery and the aorta that can occur after spinal deformity correction ( Fig. 44.90 ). Risk factors include thin habitus and spinal lengthening that occurs during scoliosis correction. Prompt recognition, bowel rest and intravenous hydration, and gradual post-pyloric feeding are essential for a good outcome, which can take several weeks. General surgical and nutritional consultation are helpful.

Atelectasis

Atelectasis is a common cause of fever after scoliosis surgery. Frequent turning of the patient and the use of incentive spirometry and deep breathing and coughing usually control or prevent serious atelectasis. Inhalation therapy with intermittent positive-pressure breathing may be beneficial in cooperative patients. With current emphasis on early patient rehabilitation, significant atelectasis has become less common.

Pneumothorax

At the time of subperiosteal posterior spine exposure, the pleura may be entered inadvertently, most commonly between the transverse processes on the concave side of the scoliosis. If a thoracoplasty is done at the same time, a pneumothorax is more likely to occur. Observation of the pneumothorax is probably appropriate if it is less than 20%, but chest tube insertion is needed for larger pneumothoraces. A Valsalva maneuver in conjunction with the anesthesia team should be performed intraoperatively if a pneumothorax is suspected so that a chest tube can be placed.

Dural Tear

If a dural tear occurs during removal of the ligamentum flavum or insertion of a hook or wire, repair should be attempted. The laminotomy often must be enlarged to allow access to the ends of the dural tear. If repair is not done, drainage of the cerebrospinal fluid through the wound can cause problems postoperatively. Larger or non-repairable tears can be managed with soft-tissue, usually muscle or fascia, patches. When large tears are repaired or patched, the patient should be left supine for 24 hours before gradual sitting to decrease intraspinal pressure.

Wrong Levels

Care should be taken in the operating room to identify the correct vertebral levels as there are normal variants in the number of ribs and segmentation at the lumbosacral junction. In most instances, an intraoperative radiograph with use of a marker on the vertebra is the best way to accurately identify the appropriate spinal level.

Urinary Complications

The syndrome of inappropriate antidiuretic hormone secretion develops in the immediate postoperative period in up to one third of patients undergoing spinal fusion. This causes a decline in urinary output and is maximal 36 hours after surgery. If the serum osmolality is diminished and the urine osmolality is elevated, this syndrome should be considered and fluid overload should be avoided. The urinary output gradually increases in the next 2 to 3 days after surgery.

Vision Loss

Postoperative loss of vision has an incidence of 0.02% to 0.2%. In a review of a nationwide database including over 40,000 patients under the age of 18 who had surgery for idiopathic scoliosis, De la Garza-Ramos et al. found that vision loss was reported in 0.16%. Prone positioning, particularly in the Trendelenburg position, has been noted to increase intraocular pressure. This is thought to be a risk factor for postoperative loss of vision as the result of decreased perfusion of the optic nerve. Other suggested risk factors include a younger age, a history of iron deficiency anemia, and long-segment fusions. The loss of vision manifests itself during the first 2 postoperative days. Most deficits are permanent.

Late complications

Pseudarthrosis

In adolescents with idiopathic scoliosis, the pseudarthrosis rate is approximately 1%, which is lower than that in patients with neuromuscular scoliosis. The most common areas of pseudarthrosis are at the thoracolumbar junction and at the distally fused segment. With more rigid and stronger implants, the pseudarthrosis may not be apparent for years. In a review of cases of nonunion with segmental instrumentation, the average time to presentation of nonunion was 3.5 years. In 23% of patients with nonunion, implant failure was detected 5 to 10 years postoperatively. The diagnosis of pseudarthrosis usually is made by oblique radiographs, a broken implant, tomograms, CT, or bone scanning ( Fig. 44.91 ). After successful posterior fusion, the disc height anteriorly should diminish as the vertebral body continues to grow at the expense of the disc space. A large disc space anteriorly may indicate a posterior pseudarthrosis. Often, however, the pseudarthrosis cannot be confirmed even with the most sophisticated radiographic evaluation and can be detected only by surgical exploration.

$FIGURE 44.91, Pseudarthrosis with rod fracture (arrows) 4 years after posterior spinal fusion in 18-year-old male.$

If a pseudarthrosis does not cause pain or loss of correction, surgery may not be necessary. Asymptomatic pseudarthrosis is more common in the distally fused segments. A pseudarthrosis at the thoracolumbar junction is more likely to cause loss of correction and pain.

During surgical exploration, the cortex is smooth and firm over the mature and intact areas of the fusion mass and the soft tissues strip away easily. Conversely, at a pseudarthrosis, the soft tissues usually are adherent and continuous into the defect; however, a narrow pseudarthrosis may be difficult to locate, especially if motion is slight. In this instance, decortication of the fusion mass in suspicious areas is indicated and a search always should be made for several pseudarthroses. An extremely difficult type of pseudarthrosis to determine is a solid fusion mass posteriorly that is not well adherent to the underlying spine and lamina. Once the pseudarthrosis has been identified, it is cleared of fibrous tissue, and the curve is reinstrumented by the application of compression over the pseudarthrosis. If this is not done, kyphotic deformity may worsen because of incompetent spinal extensor muscles from the previous surgical exposure. The pseudarthroses are treated as ordinary joints to be fused: their edges are freshened and decorticated, and autogenous bone graft is applied in addition to the instrumentation.

Crankshaft Phenomenon

If posterior fusion alone is done in patients with a significant amount of anterior growth remaining, a crankshaft phenomenon can occur (see section on treatment of juvenile idiopathic scoliosis). Combined anterior and posterior arthrodesis with posterior wire and hook constructs were recommended to eliminate anterior growth. More recent reports in the literature indicate that the use of posterior segmental pedicle screw instrumentation with three-column fixation may obviate the need for combined fusions. A report of 46 patients with interval or continuous pedicle screw instrumentation found that none had experienced crankshaft phenomenon at 3-year follow-up.

Posterior thoracoplasty

Of all the deformities caused by idiopathic scoliosis, the posterior rib prominence generally is the patient’s main concern. With thoracic pedicle instrumentation and derotation techniques, we now rarely find it necessary to perform a thoracoplasty. Chen et al. found that posterior instrumentation in combination with thoracoplasty led to a significant decrease in pulmonary function at 3 months. Eventually, the function returned to normal at 1 year postoperatively. Approximately 75% of patients have a pleural effusion on chest radiograph. If necessary for cosmetic reasons, resection of the convex ribs can improve the postoperative cosmetic result of this surgery. With the advances in posterior correction techniques and convex rib resection at the time of spinal fusion, the use of delayed thoracoplasty has fallen out of favor.

Concave rib osteotomies

Concave rib osteotomies can be used to help increase flexibility for very stiff curves. Cadaver studies have shown an average increase in deflection of 53%. Flexibility increased most when five or six ribs were resected. The addition of concave rib osteotomies to instrumentation and fusion procedures increases the risk of pulmonary morbidity and should be used sparingly because of the increased power of modern instrumentation systems and high complication rate associated with their use.

Osteotomy of the Ribs

Technique 44.22

(MANN ET AL.)

▪
Approach the concave ribs through the midline incision used for the instrumentation and spinal fusion.
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Retract the paraspinous muscles lateral to the tips of the concave transverse processes. When needed, use electrocautery to incise overlying tissue along the rib axis.
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Incise the periosteum along the rib axis for 1.5 cm lateral to the transverse process and use small elevators to expose the rib periosteally.
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Protect the pleura with the elevators and use a rib cutter to section the rib approximately 1 cm lateral to the transverse process ( Fig. 44.92A ).
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Lift the lateral rib segment with a Kocher clamp and allow it to posteriorly overlap the medial segment ( Fig. 44.92B ).
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Rongeur any jagged ends and place a small piece of thrombin-soaked Gelfoam between the rib and pleura for protection and hemostasis.
▪
Make four to six osteotomies over the apical concave vertebrae.
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Approximate the paraspinous muscles with an absorbable suture.
▪
Complete the instrumentation and fusion and insert a chest tube.

Anterior instrumentation for idiopathic scoliosis

Anterior instrumentation and fusion for idiopathic scoliosis is a well-accepted procedure for certain thoracolumbar and lumbar curves, although with newer segmental posterior instrumentation systems, the use of anterior arthrodesis and instrumentation has declined dramatically. A Lenke type 4 curve pattern in which the thoracolumbar or lumbar curve is the structural component and the main thoracic or proximal thoracic curves are nonstructural is the ideal situation for this type of procedure. Anterior instrumentation can provide de-rotation and correction of the curve in the coronal plane. The child must be old enough for the vertebrae to be large enough to allow screw fixation, and caution is advised in using these systems in children younger than 9 years. In general, the lowest instrumented vertebra is the lower end vertebra of the Cobb measurement. The proximal level usually is the neutral vertebra. The fusion should not extend into the compensatory thoracic curve above. On the convex bending film, the disc below the lowest instrumented vertebra should open up on both sides. This indicates that the lower vertebra selected can be made horizontal with the anterior approach.

The anterior approach for thoracolumbar and lumbar curves has several potential disadvantages: chylothorax; injury to the ureter, spleen, or great vessels; retroperitoneal fibrosis; and prominent instrumentation that must be carefully isolated from the great vessels. Without careful attention to detail, a kyphosing effect can occur even with solid-rod and dual-rod anterior instrumentation systems. The attachment to the spine is through relatively cancellous vertebral bodies, and proximal screw dislodgement also is a risk. Many orthopaedic surgeons require the assistance of a thoracic or general surgeon with anterior approaches.

Anterior instrumentation and fusion can also be used in the treatment of thoracic curves but has generally been replaced by posterior techniques because of the potential disadvantages of this approach, including chest cage disruption, need for a chest tube, effects on pulmonary function, the need for the assistance of a thoracic surgeon, an increased risk of progressive kyphosis because of posterior spinal growth in skeletally immature patients (Risser grade 0), and smaller vertebrae and less secure fixation, especially of the proximal screw ( Fig. 44.93 ). The aorta can be very close to the screw tips if bicortical fixation is achieved ( Fig. 44.94 ). A comparison of curve correction by posterior spinal fusion and thoracic pedicle screws with anterior spinal fusion by single-rod instrumentation in Lenke type 1 curves found that posterior spinal fusion by thoracic pedicle screw instrumentation provided superior instrumented correction of the main thoracic curves and spontaneous correction of the thoracolumbar and lumbar curves, as well as improved correction of thoracic torsion and rotation.

FIGURE 44.93, A, Standing posteroanterior radiograph of patient with idiopathic scoliosis. With posterior approach, this patient would require fusion well down into the lumbar spine. B and C, Postoperative posteroanterior and lateral radiographs after anterior instrumentation. Although some loss of fixation of proximal screw is noted, patient achieved satisfactory correction and well-balanced spine in both coronal and sagittal planes by instrumentation of only thoracic spine deformity.

FIGURE 44.94, A, CT image at T5 showing good screw position. B, With descending aorta at 2-o’clock position, 26% of distal screw was thought to be adjacent to aorta at 2 mm or less.

If the curve to be instrumented is a thoracolumbar curve, a thoracoabdominal approach is required. If the curve is purely lumbar, a lumbar extraperitoneal approach can be used.

Thoracoabdominal Approach

Technique 44.23

▪
Place the patient in the lateral decubitus position with the convex side of the curve elevated.
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Make a curvilinear incision along the rib that is one level higher than the most proximal level to be instrumented. This generally is the ninth rib in most thoracolumbar curves. Make the incision along the rib and extend it distally along the anterolateral abdominal wall just lateral to the rectus abdominis muscle.
▪
Expose and excise the rib.
▪
Enter the chest and retract the lung.
▪
Identify the diaphragm as a separate structure; it tends to closely approximate the wall of the thoracic cage. The diaphragm can be removed in two ways. We prefer to remove it from the chest cavity and then continue with retroperitoneal dissection distally. Alternatively, the retroperitoneum can be entered below the diaphragm, and then the diaphragm can be divided. To remove the diaphragm from the chest cavity, enter the chest cavity transpleurally through the bed of the rib. Then use electrocautery to divide the diaphragm close to the chest wall. Leave a small tag of diaphragm for reattachment.
▪
Once the diaphragm has been reflected, expose the retroperitoneal space.
▪
Dissect the peritoneal cavity from underneath the internal oblique muscle and the abdominal musculature.
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Split the internal oblique and the transverse abdominal muscles in line with the skin incisions and extend the exposure distally as far as necessary.
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Identify the vertebral bodies and carefully dissect the psoas muscle laterally off the vertebral disc spaces. The psoas origin usually is at about L1.
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Divide the prevertebral fascia in the direction of the spine.
▪
Identify the segmental arteries over the waist of each vertebral body and isolate and ligate them in the midline.
▪
Expose the bone extraperiosteally.
▪
The exposure from T10 to L2 or L3 with this approach is simple; but more distally the iliac vessels overlie the L4 and L5 vertebrae, and exposure in this area requires more meticulous dissection and displacement of these vessels.

Lumbar Extraperitoneal Approach

Technique 44.24

▪
Place the patient in the lateral decubitus position with the convex side up.
▪
Make a midflank incision from the midline anteriorly to the midline posteriorly ( Fig. 44.95A ).
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Divide the abdominal oblique muscles in line with the incision ( Fig. 44.95B,C ).
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As the dissection leads laterally, identify the latissimus dorsi muscle as it adds another layer: the transversalis fascia and the peritoneum. The transversalis fascia and the peritoneum diverge posteriorly as the transversalis fascia lines the trunk wall, and the peritoneum turns anteriorly to encase the viscera. Posterior dissection in this plane allows access to the spine without entering the abdominal cavity.
▪
Repair any inadvertent entry into the peritoneum immediately because it may not be identifiable later.
▪
Reflect all the fat-containing areolar tissue back to the transverse fascia and the lumbar fascia, reflecting the ureter along with the peritoneum ( Fig. 44.95D ).
▪
Locate the major vessels in the midline, divide the lumbar fascia, and carefully retract the great vessels.
▪
Divide the segmental arteries and veins as they cross the waist of the vertebra in the midline and ligate them to control hemorrhage.
▪
The skin incision must be placed carefully to ensure that the most cephalad vertebra to be instrumented can be easily seen.

Disc Excision

Technique 44.25

▪
Once the anterior portion of the spine has been exposed, the discs can be felt as soft, rounded, protuberant areas of the spine compared with the concave surface of the vertebral body.
▪
Divide the annulus sharply with a long-handled scalpel ( Fig. 44.96 ) and remove it.
▪
Remove the nucleus pulposus with rongeurs and curets. It is not necessary to remove the anterior or posterior longitudinal ligaments.
▪
Once the disc excision has been completed, remove the cartilaginous endplates with use of either ring curets or an osteotome. The posterior aspects of the cartilaginous endplates often are more easily removed with angled curets.
▪
Obtain hemostasis with Gelfoam soaked in thrombin unless a cell saver is in use.
▪
Significant correction of the curve usually occurs during the discectomies, and it becomes more flexible and more easily correctable.

Anterior Instrumentation of A Thoracolumbar Curve

Technique 44.26

▪
After exposure of the spine and removal of the discs, staples and screws are inserted into each vertebral body, beginning proximally and working distally.
▪
Place an appropriate-sized staple on the lateral aspect of the vertebral body, being sure to be posterior enough to allow placement of the anterior screw. Various staple lengths are available to accommodate different-sized patients. Normally, in the lower thoracic spine, the staple is placed just anterior to the rib head.
▪
Impact the staple into the vertebral body ( Fig. 44.97A,B ). Make a pilot hole with an awl in the vertebral body, which eliminates the need to tap the screws.
▪
In the posterior hole, insert a screw of appropriate diameter and length angled approximately 10 degrees posterior to anterior, perpendicular to the base of the staple. Leave the screw slightly elevated off the staple surface until the anterior screw is fully seated to prevent tilting of the staple ( Fig. 44.97C ).
▪
Place the anterior screws in a neutral but slightly anterior to posterior angular position. Once again, the goal is to place the screw perpendicular to the base of the staple ( Fig. 44.97D ). Bicortical purchase is required at the ends of the construct and is suggested in the intermediate levels as well. Figure 44.97E shows the staples and screws inserted from T11 to L3 before rod insertion.
▪
Decorticate the endplates before graft placement.
▪
Place intervertebral structural grafts beginning in the most caudal disc and working in a proximal direction. Structural grafts are placed in the anterior aspect of the disc to facilitate lordosis ( Fig. 44.97F ). Posteriorly, autogenous morselized rib graft is placed against the decorticated endplates.
▪
Perform appropriate biplanar bending of the posterior rod.
▪
Engage the posterior rod proximally and cantilever it into the distal screws. Capture the rod at each level with set screws ( Fig. 44.97G ). The orientation of the posterior rod is shown in Figure 44.97H prior to the rod rotation maneuver.
▪
Place the rod grippers onto the rod and rotate it 90 degrees from posterior to anterior. This will facilitate both scoliosis correction and the production of sagittal lordosis ( Fig. 44.97I ).
▪
Perform intervertebral compression across the posterior screws after locking the apical screw and compressing from the apex to both ends ( Fig. 44.97J ).
▪
Place the anterior rod sequentially into the screws and seat and lock it with mild compression forces. This is just a stabilizing rod, and no further correction is attempted. Correction in the coronal and sagittal planes can be determined on intraoperative anteroposterior radiographs.
▪
Once the final position is confirmed, break off the set screws with the counterforce device ( Fig. 44.97K ).
▪
Place one or two crosslink plates to create a rectangular construct, which increases rigidity of the system. Use the crosslink plate measuring tools to determine the required implant size ( Fig. 44.97L ) and then grasp the appropriate-sized crosslink and place it on the rods ( Fig. 44.97M and N ).
▪
The lower profile of this anterior instrumentation ( Fig. 44.97O,P ) allows the closure of the pleura distally to the junction of the pleura and the diaphragm.
▪
Complete the closure procedure. Close the diaphragm, deep abdominal layers, chest wall (after chest tube placement), muscle layers, subcutaneous tissues, and skin.

Postoperative Care

The patient is allowed up on the first postoperative day. The chest tube usually is left in place for 48 to 72 hours and is removed when the drainage decreases to less than 50 mL for two consecutive 8-hour periods. A TLSO can be used for immobilization, but if the screws have good purchase, no postoperative immobilization is used. A Foley catheter is necessary to monitor urine output because urinary retention is common. An ileus is to be expected after anterior surgery and usually lasts 2 to 3 days. Temperature elevation consistent with atelectasis is common and usually responds to pulmonary therapy and ambulation as soon as the patient is capable ( Fig. 44.98 ).

FIGURE 44.98, A, Preoperative clinical and radiographic views of 12-year-old, skeletally immature patient. B, Clinical and radiographic views after anterior spinal fusion and instrumentation from T11 to L3. SEE TECHNIQUE 44.26.

Complications and pitfalls of anterior instrumentation

Pitfalls and complications may be related to poor patient selection, poor level selection, or instrument technical difficulties. A common technical problem is failure of the most proximal screw (see Fig. 44.93 ), which can be prevented by watching this screw carefully during the derotation maneuver. At any sign of screw loosening, the correction maneuver should be stopped. Another technical problem is encountered if the screw heads are not aligned properly and one screw head is offset from the others. If one screw is off just slightly, rod placement can be difficult. Variable-angle screws or polyaxial screws allow some adjustment to account for this offset.

A number of studies have emphasized the potential complications associated with an anterior approach to the spine, including respiratory insufficiency requiring ventilatory support, pneumonia, atelectasis, pneumothorax, pleural effusion, urinary tract infection, prolonged ileus, hemothorax, splenic injury, retroperitoneal fibrosis, and partial sympathectomy.

Neurologic injury can occur during discectomy or screw insertion. The screws should be placed parallel to the vertebral endplates. When the segmental vessels are ligated, the anastomosis at the intervertebral foramina should be avoided to minimize the chance of injury to the vascular supply of the spinal cord. A scoliotic deformity is approached from the convex side of the curve, and because the great vessels are inevitably on the concave side of the curve, the risk of injury to them is low. To increase purchase of the screws, however, the opposite cortex of the vertebra should be engaged by the screw, and care must be taken to be certain that the screw is not too prominent on the concave side.

Video-assisted thoracoscopy

Video-assisted thoracoscopic surgery in the treatment of pediatric spinal deformity can be used for anterior release and instrumentation; however, it rarely is used due to similar issues related to anterior arthrodesis, a steep learning curve, and advances in posterior arthrodesis and instrumentation. Advantages of thoracoscopic surgery over open thoracotomy, in addition to better illumination and magnification at the site of surgery, include less injury to the latissimus muscle and chest wall with less long-term pain, decreased blood loss, better cosmesis, shorter recovery time, improved postoperative pulmonary function, and potentially shorter hospital stays. The primary disadvantages of thoracoscopy are related to a steep learning curve and the technical demands of the procedure. Specialized equipment is required for these procedures. A general, pediatric, or thoracic surgeon familiar with thoracoscopy and open thoracotomies should be present, and the anesthesiologist should be skilled in the use of double-lumen tubes and one-lung ventilation.

With the introduction of vertebral body tethering and spinal growth modulation, there has been renewed interest in thoracoscopic spinal approaches, although the exact indications and expected outcomes for vertebral body tethering remain unknown; they are a topic of active investigation.

Contraindications to the thoracoscopic spinal procedure include the inability to tolerate single-lung ventilation, severe or acute respiratory insufficiency, high airway pressures with positive-pressure ventilation, emphysema, and previous thoracotomy.

Video-Assisted Thoracoscopic Discectomy

Some surgeons prefer to work facing the patient with the patient in a lateral decubitus position ( Fig. 44.99A ), whereas others prefer to work from behind the patient, therefore working away from the spinal cord ( Fig. 44.99B ). Two monitors are positioned so that they can be seen from each side of the table. Because the traditional setup for most endoscopic procedures requires members of the surgical team to be on opposite sides of the patient, and because working opposite the camera image can lead to disorientation, Horton described turning the assistant’s monitor upside down. The monitor on the posterior aspect of the patient is inverted, and once the visualization port for the camera is established, the scope is inserted into the camera and rotated 180 degrees on the scope mount so that the camera is upside down. The assistant holding the inverted camera views the inverted monitor, which projects a normal monitor image as would be seen in an open thoracotomy ( Fig. 44.100 ).

Technique 44.27

(CRAWFORD)

▪
After general anesthesia is obtained by either a double-lumen endotracheal tube or a bronchial blocker for single-lung ventilation, turn the patient into the lateral decubitus position. Prepare and drape the operative field as the anesthesiologist deflates the lung. About 20 minutes is required for complete resorption atelectasis to be obtained.
▪
Place the upper arm on a stand with the shoulder slightly abducted and flexed more than 90 degrees to allow placement of portals higher into the axilla. Use an axillary roll to take pressure off the axillary structures.
▪
Identify the scapular borders, 12th rib, and iliac crest, and outline them with a marker.
▪
Place the first portal at or around the T6 or T7 interspace in the posterior axillary line ( Fig. 44.101A ).
▪
Make a skin incision with a scalpel and then continue with electrocautery through the intercostal muscle to enter the chest cavity. To avoid damage to the intercostal vessels and nerves, make the incision over the top of the rib. Insert a finger to be sure the lung is deflated and that it is away from the chest wall so it will not be injured when the trocar is inserted.
▪
Insert flexible portals through the intercostal spaces with a trocar ( Fig. 44.101B,C ).
▪
Insert a 30-degree angled, 10-mm rigid thoracoscope. Prevent fogging of the endoscope by prewarming it with warm irrigation solution and wiping the lens with a sterile fog-reduction solution. Wipe the endoscope lens intermittently with this solution to optimize visibility. Some endoscopes have incorporated irrigating and windshield-like cleaning mechanisms to further simplify the procedure.
▪
Evaluate the intrathoracic space to determine anatomy, as well as possible sites for other portals. The superior thoracic spine usually can be seen without retraction of the lung once the lung is completely deflated; however, some retraction usually is necessary below T9-T10 because the diaphragm blocks the view.
▪
Once the spinal anatomy has been identified, continue to identify levels. The first rib usually cannot be seen, and the first visually identifiable rib is the second rib. Count the ribs sequentially to identify the levels to be released. Insert a long, blunt-tipped needle into the disc space and obtain a radiograph to confirm the levels intraoperatively.
▪
Select other portal sites after viewing from within. View the trocars with the endoscope as they are inserted. Take care on inserting the inferior portal to avoid perforation of the diaphragm. Use a fan retractor to retract the diaphragm, but take care not to lacerate the lung.
▪
Divide the parietal pleura with an endoscopic cautery hook.
▪
Place the hook in the parietal pleura in the region of the disc, midway between the head of the rib and the anterior spine.
▪
Pull the pleura up and cauterize in successive movements proximally and distally, avoiding the segmental vessels.
▪
Identify the intervertebral discs as elevations on the spinal column and the vertebral bodies as depressions.
▪
For a simple anterior release, do not ligate the segmental vessels because of the risk of tearing. Bleeding can be difficult to control endoscopically. Crawford recommended coagulation of any vessels that appear to be at risk for bleeding.
▪
Vertebral body tethering instrumentation can be placed at this time.
▪
The pleura can be closed or left open.
▪
Place a chest tube through the most posterior inferior portal. Use the endoscope to observe the chest tube as it is placed along the vertebral column. Connect the chest tube to a water seal.
▪
Once the anesthesiologist has inflated the lung to determine whether an air leak exists, close the portals in routine fashion.

FIGURE 44.99, A, Conventional setup for video-assisted thoracoscopic spinal surgery. B, Setup with surgeon working away from spine. SEE TECHNIQUE 44.27.

FIGURE 44.100, A, Thoracoscopic traditional technique. B, Thoracoscopic inversion technique. SEE TECHNIQUE 44.27.

Pitfalls and complications

Bleeding can be difficult to control with endoscopic surgery. A radiopaque sponge with a heavy suture attached and loaded on a sponge stick should be available at all times to apply pressure. The suture allows later retrieval of the sponge. After application of direct pressure, electrocautery should be used for hemostasis. If necessary, endoscopic clip appliers or another hemostatic agent should be used. Instrumentation for open thoracotomy should be set up on a sterile back table to avoid delays or confusion if an immediate thoracotomy is needed to control bleeding.

Lung tissue can be damaged during the procedure. If an air leak occurs, it can be repaired with an endoscopic stapler. Cloudy fluid in the intervertebral disc space after irrigation and suctioning may indicate a lymphatic injury, which can be closed with an endoscopic clip applier. The thoracic duct is especially vulnerable to injury at the level of the diaphragm. If a chylothorax is discovered after closure, it is treated with a low-fat diet.

A dural tear can be recognized by leakage of clear cerebrospinal fluid from the disc space. Hemostatic agents can sometimes seal small cerebrospinal fluid leaks. If a dural tear continues to leak cerebrospinal fluid, a thoracotomy and vertebrectomy with dural repair may be required.

The sympathetic nerve chain on the operative side often is transected. This causes little or no morbidity; however, the surgeon needs to inform the patient and family members of the possibility of temperature and skin color changes below the level of the surgery.

Postoperative pulmonary problems often involve the downside lung, in which mucous plugs can form. The anesthesiologist should suction both lungs before extubation.

Endoscopic anterior instrumentation of idiopathic scoliosis

As experience with video-assisted thoracoscopy has increased, techniques have been developed for anterior instrumentation of the thoracic spine through a thoracoscopic approach. While the initial goal was to allow thoracoscopic anterior discectomy, fusion, and instrumentation, the most common use is now for the placement of vertebral body tethers.

Thoracoscopic Vertebral Body Instrumentation for Vertebral Body Tether

Technique 44.28

(PICETTI)

▪
Obtain appropriate preoperative radiographs and determine the fusion levels by Cobb angles.
▪
After general anesthesia is obtained by a double-lumen intubation technique (children weighing less than 45 kg may require selective intubation of the ventilated lung) and one-lung ventilation has been achieved, place the patient into the direct lateral decubitus position, with the arms at 90/90 and the concave side of the curve down. It is imperative to have the lung completely collapsed in this procedure. If the patient’s oxygen saturation drops on placement into the lateral decubitus position, have the anesthesiologist readjust the tube.
▪
Tape the patient’s hips and the shoulders to the operating table. Have a general or thoracic surgeon assist in the first part of the procedure if necessary.
▪
With the use of C-arm intensification, identify the vertebral levels and portal sites. A straight metallic object is used as a marker to identify the vertebral levels and portal sites. The superior and inferior access incisions are the most critical because the vertebrae at these levels are at the greatest angle in relation to the apex of the curve.
▪
View the planes with a C-arm in the posteroanterior plane and make sure the endplates are parallel and well defined. Rotate the C-arm until it is parallel to the vertebral body endplates, not perpendicular to the table.
▪
Position the marker posterior to the patient and align with every other vertebral body.
▪
Obtain a C-arm image at each level.
▪
Once the marker is centered and parallel to the endplates, make a line on the patient at each portal site in line with the marker. Marks should be two interspaces apart to allow placement of portals above and below the rib at each level and to provide access to two levels through a single skin incision. Use three to five incisions, depending on the number of levels to be instrumented.
▪
Once marks are made at all portal sites, rotate the C-arm to the lateral position. Place the marker end on each line and adjust the marker position until the C-arm image shows the end of the marker at the level of the rib head on the vertebrae. Place a cross mark on the previous line. This is the location of the center of the portals and will show the degree of rotation of the spine.
▪
The spine surgeon’s position at the patient’s back allows all of the instruments to be directed away from the spinal cord.

Exposure and Discectomy

▪
Prepare and drape the patient, including the axilla and scapula.
▪
Check positioning to confirm that the patient has remained in the direct lateral decubitus position. This orientation provides a reference to gauge the anteroposterior and lateral direction of the guidewires and the screws.
▪
Make a modified thoracotomy incision at the central mark. The incision can be smaller because it is used only for the central discectomies, screw placement, and viewing. The other discectomies and screw placements are done through the access portals because they provide better alignment to the end disc spaces and vertebral bodies.
▪
After the lung has been deflated completely, make the initial portal in the sixth or seventh interspace by use of the alignment marks made previously. Make sure that the portal is in line with the spine and positioned according to the amount of spinal rotation. Insertion of the first portal at this level will avoid injury to the diaphragm, which normally is more caudal.
▪
Once the portal is made, use a finger to confirm that the lung is deflated and make sure there are no adhesions.
▪
Place 10.5- to 12-mm access portals under direct observation at the predetermined positions. Count the ribs to ensure that the correct levels are identified on the basis of preoperative plans.
▪
Incise the pleura longitudinally along the entire length of the spine to be instrumented.
▪
Place a Bovie hook on the pleura over a disc and make an opening. Insert the hook under the pleura and elevate it and incise along the entire length. Use suction to evacuate the smoke from the chest cavity.
▪
Dissect the pleura off the vertebral bodies and discs. Continue pleural dissection anteriorly off the anterior longitudinal ligament and posteriorly off the rib heads by use of a peanut or endoscopic grasper.
▪
Place a Kirschner wire into the disc space and confirm the level with C-arm intensification.
▪
With electrocautery, incise the disc annulus.
▪
Remove the disc in standard fashion with use of various endoscopic curets and pituitary, Cobb, and Kerrison rongeurs. If necessary, use endoscopic shavers and rasps to assist in discectomy.
▪
Once the disc is completely removed, thin the anterior longitudinal ligament from within the disc space with a pituitary rongeur. Thin the ligament to a flexible remnant that is no longer structural but will contain the bone graft.
▪
Remove the disc and annulus posteriorly back to at least the rib head. Use a Kerrison rongeur to remove the annulus posterior to the rib heads. Leave the rib head intact at this point because it will be used to guide screw placement.
▪
Once the disc has been evacuated, remove the endplate completely and inspect the disc space directly with the scope. Pack the disc space with Surgicel to control endplate bleeding.

Graft Harvest (If Necessary)

▪
Use an Army-Navy retractor to stabilize the rib.
▪
With a rib cutter, make two vertical cuts through the superior aspect of the rib and perpendicular to the rib extending halfway across it. Use an osteotome to connect the two cuts while the retractor supports the rib.
▪
Remove and morselize the rib section.
▪
Remove three or four other rib sections in a similar fashion until enough bone graft has been obtained.
▪
If a rib is removed through an access incision, retract the portal anteriorly as far as possible. Dissect the rib subperiosteally and carry posterior dissection as far as the portal can be retracted. This technique yields an adequate amount of graft and preserves the integrity of the rib, thus protecting the intercostal nerve and decreasing postoperative pain.
▪
If the patient has a large chest wall deformity, perform thoracoplasties and use rib sections for grafting.
▪
Do not remove the rib heads at this time because they function as landmarks for screw placement.

Screw Placement

▪
Position the C-arm at the most superior vertebral body to be instrumented. It is imperative to have the C-arm parallel to the spine to give an accurate image.
▪
The vessels are located in the depression or middle of the vertebral body and serve as an anatomic guide for screw placement.
▪
Grasp the segmental vessels and coagulate at the mid–vertebral body level with the electrocautery. Hemoclip and cut larger segmental vessels if necessary.
▪
Check positioning again to ensure that the patient is still in the direct lateral decubitus position.
▪
Place the Kirschner guidewire onto the vertebral body just anterior to the rib head. Check this position with the C-arm to verify that the wire will be parallel to the endplates and in the center of the body.
▪
Check the inclination of the guide in the lateral plane by examining the chest wall and the rotation. The guide should be in a slight posterior to anterior inclination, directing the wire away from the canal. If there is any doubt or concern about the anterior inclination, obtain a lateral C-arm image to verify position.
▪
Once the correct alignment of the guide has been attained, insert the Kirschner wire into the cannula of the Kirschner guide that is positioned centrally on the vertebral body.
▪
Drill the guidewire to the opposite cortex, ensuring that it is parallel to the vertebral body.
▪
Confirm the position with the C-arm as the wire is inserted. Take care not to drill the wire through the opposite cortex because this can injure the segmental vessels and the lung on the opposite side.
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The most superior mark on the guidewire represents a length of 50 mm, and the etched lines are at 5-mm increments. The length of the Kirschner wire in the vertebral body can be determined by these marks. Start at the 50-mm mark and subtract 5 mm for each additional mark that is showing. For example, if there are four marks in addition to the 50-mm mark, the length of the Kirschner wire would be 30 mm.
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Remove the guide and place the tap over the Kirschner wire onto the vertebral body. To maximize fixation strength, use the largest-diameter tap that will fit in the vertebral bodies, based on the preoperative radiographs. Grasp the distal end of the wire with a clamp and hold it as the tap is inserted so that the wire will not advance. This is important to avoid a pneumothorax in the opposite chest cavity. Tap only the near cortex. Use the C-arm to monitor tap depth and Kirschner wire position.
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Place the appropriate-sized screw, based on the Kirschner wire measurement and tap diameter, over the wire with the Eclipse screwdriver and advance it. To ensure bicortical fixation, select a screw that is 5 mm longer than the width of the vertebral body as measured with the Kirschner wire. Grasp the wire again to avoid advancement while the screw is inserted.
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Remove the wire when the screw is approximately halfway across the vertebral body.
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Check the screw direction with the C-arm as it is advanced and seated against the vertebral body. The screw should penetrate the opposite cortex for bicortical fixation.
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Instrument all Cobb levels.
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Use each rib head as a reference for subsequent screw placement to help ensure that the screws are in line and will produce proper spinal rotation when the rod is inserted. With the screws properly aligned, the screw heads form an arc that can be verified with a lateral image.
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Adjust the side walls of the screws (saddles) to be in line for insertion of the rod. If a screw is sunk more than a few millimeters deeper than the rest of the screws, reduction of the rod into the screw head may be difficult. The C-arm image can confirm depth of screw placement as the screws are inserted.
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Once all the screws have been placed, remove the Surgicel and use the graft funnel and plunger to deliver the graft into the disc spaces. Fill each disc space all the way across to the opposite side.

Rod Measurement and Placement

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Determine the rod length with the rod length gauge. Place the fixed ball at the end of the measuring device into the saddle of the inferior screw. Then guide the ball at the end of the cable through all of the screws with a pituitary rongeur to the most superior screw and insert it into the saddle. Pull the wire tight and take a reading from the scale. The scale is in centimeters.
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Cut the 4.5-mm-diameter rod to length and insert it into the chest cavity through the thoracotomy. The rod has slight flexibility, so do not bend it before insertion.
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Apply anterior compression to obtain kyphosis in the thoracic spine.
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Do not cut the rod longer than measured because the total distance between the screws will be reduced with compression.
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Manipulate the rod into the inferior screw with the rod holder. The end of the rod should be flush with the saddle of the screw to prevent the rod from protruding and irritating or puncturing the diaphragm.
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Once the rod is in place, remove the portal and place the plug introduction guide over the screw to guide the plug and to hold the rod in position.
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Place the obturator in the tube to assist in the insertion through the incision if necessary.
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Load a plug onto the plug-capturing T25 driver. Insert the plug with the flat side and the laser etching up.
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Once the plug is placed on the driver, turn the sleeve clockwise to engage the plug with the sleeve.
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Place the plug through the plug introduction guide and insert it into the screw. Do not place the plug without using the introduction guide and the plug inserter.
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To ensure proper threading, turn the sleeve once counterclockwise before advancing the plug.
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Once the plug has been correctly started, hold the locking sleeve to prevent any further rotation. This will disengage the plug from the inserter as the plug is placed into the screw.
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Remove the driver and introduction guide and torque the screw with the torque-limiting wrench. This is the only plug that is tightened completely at this time.
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Sequentially insert the rod into the remaining screws with use of the rod pusher. Place the rod pusher on the rod several screws above the screw into which the rod is being placed.
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Apply the plugs through the plug introduction guide as described. To allow compression, do not fully tighten the plugs at this time.
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Once the rod has been seated and all the plugs are inserted into the screws, apply compression between the screws.

Compression: Rack and Pinion

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Insert the compressor through the thoracotomy incision. Once it is in the thoracic cavity, manipulate it by holding the ball-shaped attachment with the compressor holder. The rack and pinion compressor fits over two screw heads on the rod; turning the compressor driver clockwise compresses the two screws. Start compression at the inferior end of the construct with the most inferior screw’s plug fully tightened.
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Once satisfactory compression has been obtained on a level, tighten the superior plug with the plug driver through the plug introduction guide.
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Apply compression sequentially superiorly until all levels have been compressed, then torque each plug to 75 in-lb with the torque-limiting wrench. The construct is complete at this point.

Compression: Cable Compressor

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Insert each end of the cable through one of the distal holes on the side of the guide (not the larger central hole). The actuator should be in the position closest to the compressor body.
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Form a 3-inch loop at the end of the guide, with the two cable ends passing through the actuator body.
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Engage the lever arm by use of one of the plug drivers through the cam mechanism.
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Place the end of the compressor through the distal portal. With the portal removed, place a plug introduction guide through the adjacent incision, through the loop, and over the next screw to be compressed.
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Place the foot of the compressor over the rod and against the inferior side of the end screw.
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Fully tighten the plug in the end screw. Squeeze the handle of the compressor several times to compress.
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Once satisfactory compression has been obtained at a level, tighten the superior plug with the plug driver through the plug introduction guide.
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To disengage the compressor, tilt it toward the superior screw until the foot disengages from the inferior screw.
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Turn the actuator mechanism 90 degrees to disengage the ratchet.
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With the cable loop still around the plug introduction guide that is on the superior screw, pull the compressor until the actuator is next to the compressor body.
▪
Repeat the steps described on subsequent screws. Apply compression sequentially until all levels have been compressed and then torque each plug to 75 in-lb with the torque-limiting wrench. The construct is complete at this point.
▪
Place a 20-French chest tube through the inferior portal and close the incisions. Obtain anteroposterior and lateral radiographs before the patient is transferred to the recovery room.

Postoperative care

The chest tube is left in until drainage is less than 100 mL every 8 hours. Patients can be ambulatory after the first postoperative day, and they can be discharged from the hospital the day after the chest tube is removed. A brace should be worn for 3 months.

Neuromuscular Scoliosis

The specific causes of neuromuscular scoliosis are unknown, but several contributing factors are well known. Loss of muscle strength or voluntary muscle control and loss of sensory abilities, such as proprioception, in the flexible and rapidly growing spinal column of a juvenile patient are believed to be factors in development of these curves. As the spine collapses, increased pressure on the concave side of the curve results in decreased growth of that side of the vertebral body and wedging of the vertebral body itself. The vertebrae also can be structurally compromised by malnutrition or disuse osteopenia.

The SRS has established a classification for neuromuscular scoliosis ( Box 44.5 ).

BOX 44.5

Scoliosis Research Society Classification of Neuromuscular Spinal Deformity

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Primary neuropathies
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Upper motor neuron neuropathies
- Cerebral palsy
- Spinocerebellar degeneration
- Friedreich ataxia
- Roussy-Levy disease
- Spinocerebellar ataxia
- Syringomyelia
- Spinal cord tumor
- Spinal cord trauma
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Lower motor neuron pathologies
- Poliomyelitis
- Other viral myelitides
- Traumatic
- Charcot-Marie-Tooth disease
- Spinal muscular atrophy
- Werdnig-Hoffmann disease (SMA type 1)
- Kugelberg-Welander disease (SMA type 3)
- Dysautonomia
- Riley-Day syndrome
- Combined upper and lower pathologies
- Amyotrophic lateral sclerosis
- Myelomeningocele
- Tethered cord
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Primary myopathies
- Muscular dystrophy
- Duchenne muscular dystrophy
- Limb-girdle dystrophy
- Facioscapulohumeral dystrophy
- Arthrogryposis
- Congenital hypotonia
- Myotonia dystrophica

Neuromuscular curves develop at a younger age than do idiopathic curves, and a larger percentage of neuromuscular curves are progressive. Unlike idiopathic curves, even small neuromuscular curves may continue to progress beyond skeletal maturity. Many neuromuscular curves are long, C-shaped curves that include the sacrum, and pelvic obliquity is common. Hip subluxation or dislocation often is associated with the pelvic obliquity. Patients with neuromuscular scoliosis also may have pelvic obliquity from other sources, such as hip joint and other lower extremity contractures, all of which can affect the lumbar spine. Progressing neurologic or muscular disease also can interfere with trunk stability. These patients generally are less tolerant of orthotic management than are patients with idiopathic scoliosis, and brace treatment often is ineffective in preventing curve progression. Spinal surgery in this group is associated with increased bleeding and less satisfactory bone stock; longer fusions, often to the pelvis, are needed.

Many neuromuscular spinal deformities require operative intervention. The goal of treatment is to maintain a spine balanced in the coronal and sagittal planes over a level pelvis. The basic treatment methods are similar to those for idiopathic scoliosis: observation, orthotic treatment, and surgery.

Nonoperative treatment

Observation

Not all neuromuscular spinal deformities require immediate treatment. Small curves of less than 20 to 25 degrees can be observed carefully for progression before treatment is begun. Similarly, large curves in severely involved patients in whom the curve is not causing any functional disability or hindering nursing care can be observed. If progression of a small curve is noted, orthotic management may be considered if the patient can tolerate this form of treatment. If the functional ability of severely impaired patients is compromised by increasing curvature, treatment may be instituted.

Orthotic treatment

Progressive neuromuscular scoliosis in a very young patient can be treated with an orthosis. The scoliosis often continues to progress despite orthotic treatment, but the rate of progression can be slowed, and further spinal growth can occur before definitive spinal fusion. The brace also can provide patients with trunk support, allowing the use of the upper extremities.

A custom-molded TLSO usually is required for these children because their trunk contours do not accommodate standard braces. Most patients with neuromuscular scoliosis lack voluntary muscle control, normal righting reflexes, and the ability to cooperate with an active brace program; therefore, passive-type orthotics have been more successful in our experience in managing these neuromuscular curves. Patients with severe involvement and no head control frequently require custom-fabricated seating devices combined with orthoses or head-control devices.

A more malleable type of spinal brace, the soft Boston orthosis, is fabricated from a soft material that is well tolerated by patients, yet it is strong enough to provide good trunk support. The major complaint with the use of this brace has been heat retention.

Because of problems with brace treatment of neuromuscular patients, growing rods and rib-based techniques have been successfully used to control progressive neuromuscular curves. Several authors have reported improvement in the Cobb angle and pelvic obliquity with these techniques, but a deep wound infection rate of 30% also has been reported.

Operative treatment

The goal of surgery in patients with neuromuscular scoliosis is to produce solid arthrodesis of the spine, balanced in both the coronal and sagittal planes and over a level pelvis. In doing so, the surgery should maximize function and improve the quality of life. To achieve this goal, a much longer fusion is necessary than usually is indicated for idiopathic scoliosis. Because of a tendency for cephalad progression of the deformity when fusion ends at or below the fourth thoracic vertebra, fusion should extend to T4 or above. The decision on the distal extent of the fusion generally is whether to fuse to the sacrum or to attempt to stop short of it. On occasion, the fusion can exclude the sacrum if the patient is an ambulator who requires lumbosacral motion, has no significant pelvic obliquity, and has a horizontal L5 vertebral body. Many of these patients, unfortunately, are nonambulators with a fixed spinopelvic obliquity. If the spinopelvic obliquity is fixed on bending or traction films (>10 to 15 degrees of L4 or L5 tilt relative to the interiliac crest line), the caudal extent of the fusion usually is the sacrum or the pelvis. Maintaining physiologic lordosis in the lumbar spine is important in insensate patients who require fusion to the pelvis. This permits body weight to be distributed more equally beneath the ischial tuberosities and the posterior region of the thigh, reducing the risk of pressure sores over the coccyx and ischium. Bone-bank allograft usually is used to obtain a fusion.

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