Disorders of the Spinal Cord

Peripheral Nerve Roots

Peripheral nerve development is not affected in myelomeningocele. At surgery and on dissection of postmortem specimens, normal peripheral roots are found in every case. However, inside the dura mater, the roots appear to have tenuous connections with the cord itself and are occasionally hard to identify.

Vertebrae

The principal defect is the arrested development of the posterior elements (laminae and spinous process). The posterior elements may be completely absent, in which case the pedicles alone are present, or there may be partial lamina formation. In the latter case, the intraspinal canal is widened as a result of lateral displacement of the pedicles on the vertebral bodies.

Thoracic Level

Patients with thoracic-level lesions essentially have flail lower extremities and, based solely on the limbs’ total flaccid paralysis, would not be expected to develop muscle imbalance–induced lower extremity deformities. In fact, however, a frog-leg deformity is frequently present in these patients at birth, characterized by hip flexion, abduction, and external rotation contractures. In addition, there may be knee flexion and ankle equinus contractures. These may respond to judicious passive manipulation, but the hip contractures often do not respond adequately to this treatment, and the surgeon is faced with the decision whether to release the contractures to allow the lower limbs to be placed in a position for upright mobility. Occasionally, these patients develop secondary flexion deformities from spasticity in their lower extremities, which is actually presumed to be involuntary reflex motor function below the level of the myelodysplastic cord lesion. The most frequent deformities encountered by the orthopaedic surgeon in this patient group are spinal—congenital scoliosis, developmental scoliosis, and progressive congenital kyphosis.

Many patients with thoracic-level lesions can achieve exercise or household ambulation as young children. ^, All require extensive bracing above the hip and upper extremity aids (walker or crutches), and they ambulate with a swing-through gait using their upper extremities and abdominal muscles. The family must be aware that for most of these patients, this is a temporary capability. Because of the energy expenditure required for such ambulation, most patients ultimately choose to use a wheelchair full time, except for transfers. ^l

l References , , , , , , , , , , , .

Charney and co-workers found that compliant parents, physical therapy, and the absence of mental retardation were the most important factors in predicting community ambulation in children with thoracic lesions, whereas scoliosis and hip surgery were not factors. Swank and Dias found that 24% of patients with thoracic lesions were community ambulators, 41% were household ambulators, and 35% were nonambulatory (accounting for all but one of the nonambulators in the entire population); of these, 70% had associated orthopaedic defects at birth, most commonly clubfeet, kyphosis, hip dislocation, and knee-flexion deformity.

Upper Lumbar Level

Patients with upper lumbar lesions have hip flexor power and some adductor power, but no motor control of the knees or feet. For the most part, their ambulation potential and needs parallel those of patients with thoracic-level function; theoretically, however, they may be more efficient walkers as children because their hip flexor and adductor strength can be recruited to provide a better swing-through gait or, with the use of a reciprocating gait orthosis (RGO), a reciprocating gait (see later, “Orthotic Management”). This iliopsoas strength is usually not sufficient for ambulation in adolescence and adulthood, when the natural history resembles that of patients with thoracic lesions, in that they rarely continue to ambulate as adults. ^m

m References , , , , , , .

Hoffer and colleagues, however, found no differences in ambulation between adult patients with upper and lower lumbar lesions. Patients in this group experience significantly more paralytic hip dysplasia and dislocation because of imbalance at the hip, with hip flexors and adductors present, but no hip extensors or abductors.

Lower Lumbar Level

Patients with lower lumbar lesions have greater hip adductor strength and, more important, quadriceps power to provide active knee extension. Those with L5 functioning have a functioning tibialis anterior, and they may have medial hamstring function as well. Hip strength is usually adequate to allow these patients to walk with the hips unbraced—that is, with knee-ankle-foot orthoses (KAFOs). Their gait exhibits a compensatory combined maximus-medius lurch (the limb in external rotation, and a backward and lateral lean of the trunk over the hip to stabilize it in stance). Some patients may be able to walk with only ankle-foot orthoses (AFOs); however, weakness of the foot, ankle, and hip abductors and extensors leads to a lurching gait that imposes a great deal of stress on the unbraced knee. ^{, ,} These patients are also at high risk for the development of progressive hip subluxation and dislocation. Surgical treatment of the hip is most controversial in this group of patients in terms of its influence on the preservation of long-term ambulation. ⁿ

n References , , , , , , , .

In the childhood population studied by Swank and Dias, 33 of 36 patients (92%) were community ambulators, and the other 3 (8%) were household ambulators. Factors that led to decreased ambulation included deterioration of the neurologic level of the lesion, spasticity, knee and hip flexion contractures, and lack of motivation. ^, Clubfeet and hip dislocation are also frequent in this group.

Sacral Level

Patients with sacral-level myelomeningocele have near-normal knee function and more stable hip, foot, and ankle function. Their partial paralysis and insensate skin can lead to a number of foot problems, however, including cavovarus deformity, claw toes, and neurogenic ulcers. ^o

o References , , , , , , , .

Hip subluxation can occur but is less frequent than in those with lumbar lesions. Knee problems can be associated with torsional or angular stress during ambulation. ^{, , , ,} Excessive ankle dorsiflexion or external rotation may make ankle orthoses difficult to fit or ineffective in stabilizing the ankle. In theory, most sacral-level patients could ambulate without orthoses, but in practice, weak gastrocnemius and foot intrinsics result in abnormal foot and ankle function; gait studies have demonstrated that even patients with sacral-level myelomeningocele ambulate most effectively with AFOs and crutches because of stresses at the knee and weakness in the foot and ankle. ^{, ,}

Long-term reviews of patients with sacral-level paralysis are a sobering reminder of the multifactorial risk of losing neurologic function and mobility. Brinker and colleagues found that the ability to walk had declined in 11 of the 35 community ambulators (average age, 29 years), and a household ambulator had become nonambulatory; 15 patients had developed osteomyelitis, and 11 required amputations. In Selber and Dias’ report, 41 of 46 slightly younger patients (average age, 23 years) were still community ambulators, but 39 had undergone a total of 217 orthopaedic procedures and 12 had tethered cord release.

Closure of the Myelomeningocele Sac

Early closure of the sac (within 48 hours) is a cornerstone in the management of children with myelomeningocele. ^s

s References , , , , , .

Before this became the standard protocol, death was almost universal secondary to meningitis and ventriculitis. Depending on the extent of the dermal defect and underlying bony deformity (specifically, congenital kyphosis), closure can be achieved by direct approximation of the skin over the defect, with or without undermining of the skin, local rotational flaps, or musculocutaneous latissimus dorsi or gluteus maximus flaps. Defects larger than approximately 18 cm are much more likely to dehisce after primary direct closure, and consultation with a plastic surgeon is generally indicated for the purpose of covering the skin defect with a flap. ^{, ,} If required because of the underlying bony deformity, kyphectomy can be safely performed at the time of dural sac closure in neonates, with excellent initial correction. Eventual recurrence of the kyphotic deformity over time should be expected, however, despite the procedure. Fetal closure is discussed in the next section.

Hydrocephalus

The Chiari II malformation, characterized by herniation of the cerebellum and brainstem, is almost universally associated with myelomeningocele. This deformity, especially after closure of the myelomeningocele sac, produces an obstructive hydrocephalus, necessitating ventriculoperitoneal shunting in approximately 70% to 90% of infants. These shunts must be reevaluated periodically by the neurosurgeon to ensure continued function and absence of infection. Despite the presence of a shunt, the developmental delays, learning difficulties, and problems with executive functions are frequently seen in patients with myelomeningocele. ^{, , ,}

Although many patients have enlarged ventricles at birth, symptomatic hydrocephalus usually develops only after closure of the myelomeningocele sac. Thus many infants undergo closure of the sac within 48 hours of birth, develop hydrocephalus, and then undergo ventriculoperitoneal shunt placement. A study comparing staged and simultaneous sac closure and shunting found that patients treated by the simultaneous technique had a significantly reduced incidence of wound leakage at the closure site and no deleterious effects with respect to shunt failure, hydrocephalus, or CSF infection.

There is increasing evidence that the neurologic deficits in myelomeningocele patients are caused by the primary myelodysplasia compounded by exposure of the neural elements to amniotic fluid in utero. ^{, ,} As noted, this led to the development of fetal surgical techniques to close the sac in utero in the hope of limiting the secondary neurologic injury. Preliminary reports in the small group of patients treated in this way have suggested that the need for ventriculoperitoneal shunting is reduced, from 90% to 60%. However, fetal surgery is associated with maternal and pregnancy complications, premature birth chief among them. Brainstem compression, presumably by the Chiari II malformation, can lead to respiratory obstruction and apnea. Sleep disturbances related to air hunger, dyspnea, and squeaky voice may all require assessment by a neurosurgeon for the possible presence of brainstem compression as the cause of these complaints.

Other Spinal Cord Abnormalities

Patients with myelomeningocele are subject to a number of other spinal cord lesions that may require assessment or treatment by a neurosurgeon, including hydromyelia, diastematomyelia, and tethered cord syndrome. ^t

t References , , , , , , , , , , .

Hydromyelia (sometimes termed hydrosyringomyelia ) is a dilation of the central canal of the spinal cord. This lesion is often detected as an asymptomatic finding on MRI, but has been implicated in upper extremity weakness or spasticity in some patients; thus patients with these clinical findings should undergo MRI and neurosurgical evaluation. ^{, ,} Diastematomyelia is a congenital anomaly of the spinal cord and column consisting of a central splitting of the spinal cord by a fibrous, cartilaginous, or bony spicule (diastematomyelia is also discussed in [CR] ). Myelomeningocele patients with other congenital vertebral anomalies may have an associated diastematomyelia, which should be investigated by MRI if there is hypertrichosis, progressive lower extremity weakness, spasticity, or back pain or if corrective spinal surgery is planned.

Tethering of the spinal cord in scar tissue at the site of repair of the initial myelodysplastic lesion may be the source of significant symptoms as the child grows. ^u

u References , , , , , , , , , , , .

Symptoms attributed to the presence of a clinically significant tethered spinal cord include back pain, especially at the site of sac closure, progressive lower extremity weakness, lower extremity spasticity, progressive foot deformity or scoliosis, and changes in bladder habits and function. Because a low-lying conus suggesting spinal cord tethering is demonstrated on MRI in almost all patients ( Fig. 32.7 ), ^, the diagnosis of tethered cord is usually based on the presence of one or more of the symptoms or signs noted earlier, typical MRI findings, and exclusion of hydromyelia or shunt malfunction as an alternative explanation. Evidence of deterioration in somatosensory evoked potentials or urodynamic testing has been used by some to document symptomatic tethering of the spinal cord. ^{, ,}

Sarwark and associates found that back pain resolved after surgical untethering, and curves stabilized or improved in 60% of patients with scoliosis and in 78% of patients with lower extremity weakness. Spasticity was least affected by surgical untethering, improving in only 43% of patients but stabilizing in the remainder. Pierz and colleagues reported that patients with curves less than 40 degrees experienced some improvement after an untethering procedure, but those with curves more than 40 degrees or thoracic neurologic levels had no improvement in scoliosis. McLaughlin and co-workers found that intraspinal rhizotomy and distal cordectomy were effective in ameliorating symptoms and lower extremity deformities caused by spasticity in patients with thoracic lesions. However, this treatment is indicated only for patients with no voluntary lower extremity function and in whom symptoms of spasticity cannot be controlled with lower extremity bracing or surgery.

Goals of Orthopaedic Management

Orthopaedists participating in the care of children with myelomeningocele are members of the health care team seeking to maximize function and minimize disability and illness. Over time, the specific goals change, based on the child’s needs and abilities and changes in neurologic status. One of the major goals of the orthopaedist is to correct deformities to help patients meet their maximal functional capability. Almost all patients need orthoses to replace muscle strength and joint stability so that they can stand and walk. Regardless of the extent of the deformity and paralysis, it is possible for most children to walk at a young age with a combination of deformity correction, bracing, upper extremity aids, and instruction. Thus one of the primary functions of the orthopaedist is to correct lower extremity deformities that prevent the patient from using orthoses to ambulate during childhood. Many patients, especially those with thoracic or upper lumbar paralysis, will be unable or unwilling to maintain the same level of independent ambulation as adolescents or adults because the extent of bracing and energy consumption required for ambulation will be too great. Patients with myelomeningocele should be prepared for independent, self-sufficient living, which means that they should not be devoting a substantial portion of their energy solely to walking for its own sake. Excessive emphasis on ambulation over the use of a wheelchair may even adversely affect academic achievement.

The orthopaedic surgeon must monitor spinal balance and deformity in the myelomeningocele patient. There is a high incidence of congenital and neurologically related scoliosis and kyphosis, conditions that can jeopardize posture or sitting comfort or increase the likelihood of the development of pressure sores.

Finally, the orthopaedic surgeon must assist in monitoring the neurologic status of the growing patient. Hydrocephalus, hydromyelia, or tethered cord syndrome secondary to diastematomyelia or another anomaly, or to scarring at the original level of myelodysplasia, can occur. Any of these conditions can result in a subtle deterioration in the patient’s intellectual function and upper or lower extremity function.

In an effort to help orthopaedic surgeons understand what is required to achieve treatment goals for this complex disorder, experts from around the world convened in a symposium in 2000. The discussions from that meeting were published in a comprehensive report from the American Academy of Orthopaedic Surgeons describing the many facets of the orthopaedic care of children with spina bifida.

Physical and Radiographic Examination of the Newborn

When examining a newborn with myelomeningocele for the first time, the goal of the orthopaedic surgeon is to identify the level of paralysis for each extremity and screen for associated deformities. Sphincter control, the presence of hydrocephalus, and the condition of the myelomeningocele sac are also important to note. Commonly, the orthopaedist is consulted after closure of the sac and shunting for hydrocephalus. The infant should be examined in a quiet warm environment to allow the best assessment of joint range of motion, sensory preservation, and evidence of spinal deformity. A stimulated or crying infant, however, allows the examiner to appreciate the child’s voluntary lower extremity muscular function better. Sharrard described the neurosegmental function of the lower extremity, ^, and this root-by-root assessment has become the standard for describing lower extremity function and the basis for establishing a prognosis for long-term ambulation and the nature of secondary deformities likely to develop during childhood. The level of spinal cord lesion as visualized on prenatal ultrasonography has been positively correlated with the level of postnatal paralysis noted on physical examination, so if this information is available, it may be helpful. Caution is advised, however, because determining the precise level of function can be difficult, and the level may change over time, may be asymmetric, or may not correspond exactly to Sharrard’s neurosegmental scheme. ^{, ,} In a longitudinal serial evaluation of 308 patients older than 5 years, McDonald and colleagues found that quadriceps strength correlated with iliopsoas strength, medial hamstring function could be present without tibialis anterior function, gluteus medius and maximus strength correlated strongly with each other and with tibialis anterior strength, and muscle weakness was most frequently noted in the gastrocnemius-soleus group.

During the examination, the orthopaedist should first develop a sense of the child’s overall vigor because lack of vigor may suggest CNS depression caused by untreated hydrocephalus. Whenever expedient, the examiner should turn the infant prone on the mother’s lap, an examining surface, or the palm of the examiner’s hand to determine at what level the myelodysplastic deformity is located, its extent, and the state of the skin overlying it, especially if the examination is being conducted after neurosurgical closure of the myelodysplastic lesion. The infant should also be assessed for obvious spinal deformities or congenital scoliosis or kyphosis associated with the myelodysplastic lesion. The examiner then looks for more subtle evidence of spinal dysraphism at other levels—specifically, for discoloration or hemangiomas, hairy patches, or dimpling along the spinal column remote from the obvious myelodysplastic lesion. The entire spinal column is palpated, with the examiner looking for curvature or defect.

With the child supine, neck mobility and upper extremity formation and function are assessed; these are generally normal in the myelomeningocele patient. Next, the examiner visually inspects the posture of the lower extremities, which provides a clue to the extent of the paralysis. For example, a child with a thoracic-level lesion most often lies supine with the legs in a flopped-open, frog-leg position, with no spontaneous movement. Patients with lower levels of paralysis exhibit spontaneous movement of the lower extremities; if necessary, the examiner can stimulate the child to observe such movement. Specifically, the examiner should look for hip flexion and adduction, knee extension and flexion, and ankle dorsiflexion and plantar flexion. A note of caution is in order, however, because observed toe movements should not be taken as indicative of volitional control of the digits, and movement of the toes usually results from root sparing below the myelodysplastic lesion and is not under volitional control. The examiner should try to assess the level of preservation of sensation by gently stroking the skin, beginning distally, and observing the infant’s facial and lower extremity muscular response. The examiner checks for the usual obvious foot deformities, such as clubfoot and vertical talus. Range of motion of the hips is assessed, with specific noting of abduction, adduction, external rotation, and/or flexion contractures. The hips are also assessed for concentricity and stability. Knee-flexion contractures and their extent should be documented. The examiner strokes the patient’s legs on both sides individually, from distal to proximal, by dermatome, to identify the level of sensory preservation. Finally, the examiner checks for the almost invariably present patulous anus and urinary dribbling, suggesting bowel and bladder paralysis.

The physical examination should be supplemented with good anteroposterior and lateral radiographs of the entire spine. These radiographs should be carefully inspected for the level of the last closed posterior element, any congenital spinal deformity (particularly one remote from the myelodysplastic level), and pedicular widening, especially with associated congenital vertebral anomalies, which may suggest underlying diastematomyelia. In general, the level of paralysis noted on physical examination should correspond to the first open level of the spine; however, there may be a substantial discrepancy between these two findings, which suggests that other deformities of the spinal cord or proximal CNS are contributing to the paralysis. Ultrasonography or MRI of the spinal cord may be indicated in these cases. In general, radiographs of the lower extremities merely confirm what has been determined from the physical examination. Ultrasonography can clarify the relationship of the femoral head and acetabulum if the clinical examination of the hip is not definitive.

This examination provides the orthopaedic surgeon with a good understanding of the lower extremity anomalies, extent of lower extremity paralysis, and presence of vertebral anomalies that need to be monitored with growth. The sum of these findings allows the surgeon to provide the patient’s parents with a reasonable outline of what will be required to correct the deformities and what they should expect in the future in terms of bracing needs and mobility expectations.

Periodic Assessment

Patients with myelomeningocele require periodic reassessment throughout growth, usually on a semiannual or annual basis. These assessments are typically carried out in a multidisciplinary clinic; this reduces the number of physician visits for the patient and family and allows the health care team to provide a comprehensive evaluation and coordinated treatment plan when interventions are required. Within this complex screening and treatment program, at each routine visit, the orthopaedist assesses whether the following are present:

• 1.

  The child’s motor and sensory functions have remained stable.

• 2.

  The child’s mobility and bracing needs have remained stable.

• 3.

  Orthoses and upper extremity aids are appropriate to the patient’s requirements, provide the desired effect of maximizing mobility, are in good repair, and are not causing any undue pressure points on the patient’s lower extremities.

• 4.

  The range of motion of the patient’s lower extremity joints is stable and sufficient to allow the patient maximum mobility based on preserved motor strength.

• 5.

  The patient’s upper extremity function is stable.

• 6.

  Spinal deformity is stable or absent.

• 7.

  The patient’s skin is in good condition over the spinal deformity, in the perineal and ischial areas, at pressure points under orthoses, and over the knees and around the feet, where abuse of the skin may occur with crawling, walking, or swimming without braces or other protection.

These evaluations may be accomplished with the aid of a nurse, pediatrician, therapist, and orthotist. Periodic radiographic assessment of the spine and hips is often required as well; it is rare that a patient has no evidence of spinal or hip deformity on physical examination.

Foot and Ankle Deformities

Congenital and developmental foot deformities are common in children with myelomeningocele. ^{, , , ,} Calcaneal deformity is the most common, followed by equinus, valgus deformity, clubfoot, and vertical talus. Foot deformities often interfere with effective bracing for ambulation or lead to pressure sores in ambulatory patients. Broughton and colleagues found that acquired deformities could not be accounted for solely by spasticity or muscle imbalance. Even nonambulatory patients have concerns about the cosmetic appearance of the feet and experience difficulty wearing normal shoes.

In general, foot deformities in an infant should undergo a trial of gentle passive manipulation, with care taken to avoid pressure sores and fractures. Even with early correction, recurrence is common, and surgery is ultimately needed on most feet. When required, it is important that surgical correction be delayed until the child is developmentally ready to be in the upright position. Proceeding with surgery for foot deformity before the patient is ready to be fitted with orthoses for standing or walking risks recurrence before the child even begins to walk. Early recurrence of the deformity can be minimized by ensuring that after the removal of postoperative casts, well-fitting orthoses are immediately available for use day and night, and the child should be encouraged to stand or walk in them.

Equinus

Pure equinus contractures in patients with myelomeningocele are common. ^{, ,} They are not caused by voluntary muscle imbalance, however, because most patients have flail feet or, in patients with low lumbar lesions, tibialis anterior functioning. Positioning deformity, in utero or postnatally, and gastrocsoleus spasticity account for some of the equinus contractures seen and, in some patients, equinus develops after tibialis anterior tendon transfer to the calcaneus (see later, “Calcaneal Deformity”).

Patients with positional neonatal equinus contractures associated with higher-level paralysis can initially be treated with extremely gentle passive manipulation. If the equinus deformity persists when the child is ready for orthoses for standing and ambulation, percutaneous release or open lengthening of the heel cord can be carried out. Percutaneous heel cord lengthening can be performed in the outpatient clinic if the patient is insensate in that area. Some patients have long toe flexor contractures as well, which should be divided. Otherwise, persistent toe flexion deformities can result in pressure sores on the ends of the toes when the child is placed in shoes. Careful postoperative casting for a few weeks should be followed by the fitting of orthoses required for standing or ambulation.

Equinovarus

Clubfoot deformity is common in patients with myelomeningocele, regardless of the level of myelodysplasia. ^x

x References , , , , , , , , , , .

This deformity in myelomeningocele patients is truly teratologic in that the deformity is almost always rigid, with less propensity to respond to conservative treatment, requires extensive surgery to correct, and is likely to recur, even after excellent correction combined with resection of the tendons that would presumably be the source of recurrence. ^y

y References , , , , , , , , , .

Patients with myelomeningocele and clubfoot deformity can initially be managed in a manner similar to other patients with idiopathic clubfoot deformity (see Chapter 19 ). However, the treating physician should be very experienced and comfortable with manipulation and casting techniques because absence of the pain response or of protective sensation makes it difficult to avoid pressure sores or fractures. One report noted favorable results with use of the Ponseti method to treat clubfeet associated with myelomeningocele. However, despite excellent initial correction, the authors noted relapse in 68% of patients, and a need for comprehensive soft tissue release in 14% of patients, four times more frequent than found with idiopathic patients. A recent report noted successful initial treatment of the clubfeet by the Ponseti technique in 11 children with 18 affected feet. Correction was satisfactory in 83% at 4.5 years average follow-up. One-third of the feet recurred, and were managed successfully with a second period of casting and Achilles tenotomy.

When nonoperative or minimally invasive techniques fail, extensive release is often required, and ancillary procedures such as lateral column shortening are required much more frequently than in patients with idiopathic clubfeet. In patients with lower lumbar lesions, the tibialis anterior tendon may be lengthened or transferred to the midline or heel (see later, “Calcaneal Deformity”). In patients with upper lumbar or higher lesions, tendons are frequently resected rather than lengthened. Only in patients with almost complete preservation of lower extremity function is typical tendon lengthening performed, rather than resection. Furthermore, much as in patients with arthrogryposis, myelomeningocele-related clubfeet may require naviculectomy, talectomy, ^{, , , ,} or talar enucleation (Verebelyi-Ogston procedure) to achieve correction. Infrequently, in the most severe deformities, bringing the foot into a corrected position may cause vascular compromise, requiring combined clubfoot correction and tibial and fibular shortening. Difficulty with wound closure is common, and rotational flaps have been described for primary closure of the surgical incision. I have found, however, that it is most effective to leave the wound open as much as necessary with the foot in the corrected position, provided that circulatory status is not impaired in that position, and to change the cast or window it for dressing changes. An alternative is to close the skin loosely and bring the foot into a corrected position with a few cast changes in the first 2 weeks after surgery. Inadequate skin coverage for surgical correction of recurrent clubfoot deformities has been addressed with the preoperative use of soft tissue expanders, but with only limited success (in two of seven cases).

Postoperative casting must be meticulous, as described earlier. Excessive swelling, erythema, or systemic reaction must be investigated by removing the cast and inspecting the foot. Wound necrosis and pressure sores are frequent, even with casting by the most experienced and attentive of surgeons, and families should be so warned. Bracing of at least the foot is required indefinitely after cast removal, so the surgeon should ensure that the required orthoses are ready to be applied when the cast is removed. The postoperative casting protocol may be shortened in favor of braces, compared with that in patients with idiopathic clubfeet. ^{, ,}

Recurrence of deformity can be treated by primarily bony procedures, including midfoot and forefoot osteotomies, talectomy, or triple arthrodeses. ^{, , , ,} When using these procedures, the surgeon must be careful to obtain even weight-bearing forces to minimize the predisposition to the development of neurotrophic ulcers. A variation of equinovarus deformity may be seen in patients with lower lumbar paralysis with a functioning anterior tibialis. In some of these patients, a deformity consisting of primarily forefoot dorsiflexion and supination gives the impression of a deformity caused solely by the unopposed action of the tibialis anterior or a very mild clubfoot. In infants with such a deformity, posterior or lateral transfer of the tibialis anterior alone may not correct all components of the deformity, and a limited posteromedial release is often required as well.

Calcaneal Deformity

Calcaneal deformity may be seen as a birth contracture or as a delayed deformity secondary to the unopposed action of the tibialis anterior in patients with paralysis at the lower lumbar level. ^z

z References , , , , , , , .

Not all developmental calcaneal deformities can be explained solely on the basis of muscle imbalance or spasticity. ^, Calcaneal deformity of the foot may make the fitting of orthoses more difficult and less effective, and it predisposes patients to the development of neurotrophic heel ulcers. The latter can be difficult to eradicate and may progress to recalcitrant calcaneal osteomyelitis ( Fig. 32.8 ). Patients with progressive calcaneal deformity or those with a propensity toward ulcer development can be treated surgically to prevent this from occurring. In one study, a delay in surgical treatment of this deformity resulted in a 10-fold increase in the prevalence of calcaneal ulcers, from 3% to 30% of ambulatory patients.

Patients with mild calcaneal deformities from birth, with the possible exception of those with tibialis anterior–sparing involvement, may respond to gentle passive stretching of the foot into plantar flexion and splinting in a neutral, weight-bearing position. Patients with persistent or progressive calcaneal deformities associated with unopposed tibialis anterior function frequently require anterior release of the deformity, usually combined with posterior transfer of the tibialis anterior to the calcaneus to facilitate brace fitting and prevent the development of calcaneal plantar ulcers. ^aa

aa References , , , , , , , .

The transfer is not performed if this muscle is spastic. The tibialis anterior muscle transfer procedure is described in Plate 32.1 . A few important points should be made with regard to this surgery. First, in patients with low lumbar lesions, a posterior transfer performed in the hope of providing enough ankle stability to make braces unnecessary usually does not succeed; AFOs continue to be needed for maximum mobility. Second, the transfer should be positioned with the foot in a neutral position and, postoperatively, the foot should be immobilized in a neutral position in a cast, not in equinus. If the foot is positioned in a plantar-flexed position, the patient may sustain a distal tibial metaphyseal fracture after cast removal when the foot is dorsiflexed with weight bearing. Finally, excessive tightening of the transfer in equinus may result in the development of an equinus deformity that requires release, particularly when the transferred tibialis anterior is not under volitional control.

Vertical Talus

Congenital vertical talus occurs with greater frequency in patients with myelomeningocele than in the general population, although it is much less common than clubfoot and other deformities of the foot. ^{, ,} The manipulative treatment discussed for the management of vertical talus in Chapter 19 may be used in patients with myelomeningocele. However, the treating surgeon must be cognizant of the increased likelihood of pressure sores and recurrence of deformity. Patients with vertical talus and spina bifida usually require surgical correction, which is the same as for any patient with congenital vertical talus (see Chapter 19 ). The principles of timing and postoperative management raised in the discussion of clubfoot in patients with myelomeningocele apply here as well. Specifically, surgery should be delayed until the patient is neurodevelopmentally ready for orthoses and ambulation. Postoperative casting must be meticulous and must hold the foot in a neutral functional position, and bracing and weight bearing should be instituted as soon as the casts are removed.

Valgus Deformity of the Foot and Ankle

Valgus deformity at the ankle is a common deformity in ambulatory patients with myelomeningocele, irrespective of the level of paralysis. ^bb

bb References , , , , , , , , , , .

The deformity may arise from the distal tibia, the subtalar joint, or both and may be compounded by an external rotation deformity of the tibia. The most common sequela of this deformity is skin irritation or breakdown over the medial malleolus from excessive pressure against the orthosis ( Fig. 32.9 ). Important considerations for the orthopaedic surgeon include determining the precise location of the clinical valgus (ankle or subtalar), ascertaining whether the patient is skeletally mature and, if immature, approximately how much growth remains in the distal tibia, and deciding whether the extent of deformity requires immediate correction because it is unbraceable, or whether more gradual methods of correction can be used. Thus assessment requires a physical examination of the patient, consultation with an orthotist regarding the interim management of medial malleolar pressure areas, and anteroposterior radiographs of the ankle to determine the source of the valgus and state of the physis. In skeletally immature patients, a scanogram and radiographs of the hand and wrist for estimation of bone age may be necessary to assess how much growth remains in the distal tibia if distal tibial epiphysiodesis techniques are being considered.

Distal Tibia

Surgical options for the management of distal tibial valgus deformities include distal tibial and fibular osteotomy, ^{, ,} distal tibial medial hemiepiphysiodesis or growth tethering with implants such as staples, screws, and plates, ^, and Achilles tendon–distal fibular tenodesis. A distal tibial valgus deformity that causes pressure sores and cannot be corrected by adjustment of orthoses, or such a deformity in a skeletally mature patient, requires a distal tibial osteotomy and varus realignment ( Fig. 32.10 ). Skeletally immature patients with deformities that are progressive but not in need of immediate correction are candidates for medial tibial hemiepiphysiodesis or Achilles tendon–fibular tenodesis. The medial growth arrest may be affected by direct curettage, stapling of the medial side of the distal tibia, or insertion of a fully threaded screw percutaneously from the medial malleolus proximally across the physis. Historically, an Achilles tendon–fibular tenodesis is indicated for young patients with mild distal tibial valgus deformities who are considered too young for an epiphysiodesis of the distal tibia, although we currently rarely perform this procedure.

Distal Tibial Osteotomy

Fixation may be done with crossed Steinmann pins, staples, external fixator, or internal fixation with a dynamic compression plate. This osteotomy may be complicated by delayed union, nonunion, or infection, particularly in adolescents. Recurrence of the deformity is also relatively common in skeletally immature patients. Postoperatively, patients should be kept non–weight bearing initially because weight bearing with diminished pain perception can lead to excessive swelling and motion. Patients should also be counseled not to crawl in postoperative casting. If possible, the knees should not be flexed excessively in long-leg casts because this can cause rehabilitation difficulties after cast removal.

Distal Tibial Medial Hemiepiphysiodesis

If the patient is skeletally immature, with a deformity that does not demand full and immediate correction, a medial hemiepiphysiodesis can be considered. The medial tibial physis can be closed with direct surgical ablation, stapling, or insertion of a medial malleolar screw. The advantages of this technique are that immediate weight bearing is usually allowed and external immobilization is not necessary.

Achilles Tendon–Fibular Tenodesis

Stevens and Toomey described the tenodesis of a portion of the Achilles tendon to the distal fibula above the distal fibular physis. Their rationale was that the valgus deformity is secondary to lateral compartment paralysis, with subsequent underdevelopment of the fibula, and that this lack of growth stimulation can be compensated for by tenodesis of a slip of the Achilles tendon to the fibula. With weight bearing and ankle dorsiflexion, the tenodesis pulls downward on the fibula, leading to gradual correction of the deformity. The surgical procedure is outlined in Plate 32.2 . Similar to distal tibial hemiepiphysiodesis, this procedure is indicated for skeletally immature patients with progressive deformities that do not yet require complete correction. It is particularly well suited for younger patients in whom hemiepiphysiodesis is not appropriate.