An Approach for Treatment of Complex Pediatric Spinal Deformity

Growth of the Spine

PSDs may become evident, and characteristically progress rapidly, during growth periods. Therefore, anticipating and modifying the growth potential of the vertebral elements composing the deformity is essential. Two periods of rapid growth occur in children: the first between birth and 3 years, and the second during the adolescent years. The timing and duration of the adolescent growth spurt can be determined by monitoring the growth velocity ( Fig. 143.4 ). The spine grows heterogeneously—that is, during the adolescent growth spurt, the thoracic spine grows 1.2 cm per year and, in contrast, the lumbar spine grows 0.6 cm per year. Measuring, estimating, and monitoring the changes in sitting height (thoraccolumbar segmental growth) during growth spurts can be helpful for growth velocity determination and for treatment planning. The presence of scoliosis and other vertebral anomalies (mainly apical) can exacerbate the multiplanar deformity during growth spurts. Other associated conditions, including neuromuscular and connective tissue disorders, that may affect the progression of the curve should also be considered in monitoring and management.

Predicting growth around the time of puberty is based on physical and radiographic examinations. In girls, Tanner stage 2 (development of pubic hair and breast buds) marks the onset of the growth spurt and typically precedes menarche. Skeletal age at this stage is approximately 11.5 years. The growth spurt ends at a skeletal age of 14 years, or approximately 1.5 years after menarche. For boys, Tanner stage 3, when the pubic hair becomes curly, corresponds to the onset of the growth spurts. The skeletal age is approximately 13 years and continues until 18 years. A growth rate chart is the ideal means of monitoring growth, but realistically this is not always feasible to obtain. Otherwise, the surgeon should consider physical findings, such as the Tanner stage, in conjunction with historical information regarding the onset of menarche or the appearance of axillary hair in boys.

Several methods for the assessment of skeletal maturity have been reported, including Risser stage, presence of triradiate cartilage, and hand films. The Risser stage is a method based on the degree of iliac ossification, with stages 1 through 4 corresponding to sequential ossification of each quarter of the iliac crest from ventral to dorsal ( Fig. 143.5 ). Stage 4 reflects completion of spinal growth, and stage 5 is defined as fusion to the ilium. Alternatively, hand films can be obtained for the assessment of skeletal maturity, without the need to expose the pelvis to radiation, as is required for both the Risser stage and assessment of the triradiate cartilage. ^, Use of more than one method in assessing skeletal maturity can provide a more accurate estimate of growth potential. ^{, ,} Assessment of the growth potential of the spine is important to determine the prognosis regarding likelihood of curve progression, to determine the role of tethering in correction of deformity, and to determine whether anterior column overgrowth after posterior fusion (crankshaft phenomenon) is likely.

The rib–vertebral angle difference (RVAD) is a radiographic measure that can be useful in guiding decision-making in infantile spinal deformity. This measure is an important prognostic indicator for infantile scoliosis. The RVAD is the difference between the angles formed by a line along the rib head and perpendicular to the base of the apical vertebra on the right and left sides of the spine. Spontaneous resolution of the scoliosis is expected in 85% to 90% of cases if the RVAD is less than 20 degrees, but progression is expected with an RVAD greater than 20 degrees.

Evaluation

Clinical Evaluation

Initial evaluation should begin with a detailed history regarding the prenatal and perinatal events and cognitive and motor development progression since birth. Details of the suspected spinal disorder should be documented, including symptoms, deficits, onset, and progression, as well as disability and impact on quality of life. Past medical history can be a significant contributor, especially with congenital spinal disorders, which can be associated with other anomalies.

Physical examination should include assessment of the head, entire spine, and extremities, including the skin; it should also encompass a detailed neurological examination, including strength, tone, gait, coordination, sensation, and physiological and pathological reflexes. For example, neurofibromatosis may be suggested by the presence of café au lait spots or freckling, and patches of hair or skin dimpling can evidence underlying anomalies such as diplomyelia or lipomeningocele. Nonambulatory patients should be examined for evidence of decubitus ulceration, which may affect surgical planning. Posture should be assessed and may include sitting, standing, and walking.

The scoliometer or inclinometer is used to quantify the rib prominence and paralumbar prominence. A scoliometer reading greater than 5 degrees is associated with a scoliosis of at least 10 degrees ( Fig. 143.6 ).

Imaging Evaluation

Initial evaluation of suspected spinal deformity often includes full-length (36-inch) posteroanterior (PA) and lateral spinal radiographs to assess global and regional spinal alignment. PA images evaluate scoliosis, with measures including Cobb angle and coronal balance. Coronal balance is measured as the distance between a vertical line from the center of the C7 vertebral body (C7 plumb line) and the central sacral vertical line (CSVL) ( Fig. 143.7 ). Lateral full-length spinal radiographs are used to assess for regional kyphosis and lordosis and for global sagittal alignment. Global sagittal alignment is measured as the distance between a vertical line from the center of the C7 plumb line and the dorsal rostral corner of the S1 vertebral body. If the C7 plumb line is ventral to the dorsal rostral corner of the S1 vertebral body, the sagittal alignment measure is recorded as a positive value, and if dorsal, it is recorded as a negative value.

The flexibility of scoliotic curves can be assessed with side-bending PA films to the left and to the right either in standing or in supine position with the patient placed over a bolster or with the use of traction. Supine bending radiographs have been suggested to be more useful in assessing the flexibility than standing films. The flexibility of kyphotic deformities can be assessed with a bolster placed under the apex of the kyphosis, and the flexibility of lordotic deformities may be assessed with the spine and pelvis placed in flexion. Traction-assisted radiographs are more useful in the setting of larger curves (Cobb angle >65 degrees) and in patients with neuromuscular disorders with contractures. This information can provide an estimate of surgical curve correction and can help in the assessment of whether the secondary curves are structural or nonstructural, and whether secondary curves may need to be included in the fusion.

Computed tomography (CT) imaging provides greater detail of the bony anatomy and a three-dimensional view of complex deformities; such information may facilitate planning of surgical treatment. ^, CT can better define congenital deformities with underlying anomalies, such as hemivertebra or unsegmented bars, that may be occult or not well-defined on plain-film radiographs ( Fig. 143.8 ).

In the setting of spinal deformity, magnetic resonance imaging (MRI) can be used to evaluate for central canal and foraminal stenosis, as well as for underlying abnormalities, which may warrant treatment or alter surgical planning. Associated abnormalities, such as tethered cord, syringomyelia, and tumors, occur in up to 15% to 38% of congenital spinal deformity patients ( Fig. 143.9 ). Although MRI is often used as an adjunct in the imaging evaluation of PSD, several specific indications necessitate this evaluation, including severe pain; neurological findings, including motor weakness, muscle atrophy, and upper motor neuron signs; early-onset scoliosis with a Cobb angle greater than 20 degrees; atypical scoliosis curve patterns (e.g., left thoracic curves, sharp angular curves, congenital deformities, and curves that are >70 degrees); scoliosis curves with a rapid progression (>1 degree per month); neurofibromatosis; deformity associated with myelomeningocele; and lack of apical lordosis in idiopathic scoliosis ^, ( Fig. 143.10 ).

Idiopathic Scoliosis: Early Onset and Adolescent Onset

Idiopathic scoliosis has a familial tendency and a bimodal frequency distribution. With the early-onset type, the majority of cases occur in infancy, and a second major peak arises during adolescence. Idiopathic scoliosis is divided into two groups: early onset (<5 years) and late onset (5 years to skeletal maturity). ^, The most common type is adolescent idiopathic scoliosis (AIS).

The diagnosis of AIS is one of exclusion. In idiopathic scoliosis, deformity is the most common reason for referral. Occasionally, low-grade, activity-related back pain can result from lumbar curves or curves greater than 40 degrees. Atypical cases demand further evaluation to establish a diagnosis. ^,

The prevalence of AIS with a curve of at least 10 degrees is 2% to 3% of the adolescent population. Curves in excess of 20 degrees have a prevalence of 0.3% to 0.5%, whereas the prevalence of curves in excess of 40 degrees is 0.1%.

Curves originating before the age of 5 years can exceed 100 degrees and affect both the cardiac and pulmonary systems. Thus, treatments are determined by patient age, growth potential of the spine, and degree of deformity.

Adolescent Idiopathic Scoliosis