Cobb Angle Progression in Adolescent Scoliosis Begins at the Intervertebral Disc

Abstract

Study Design-Longitudinal radiographic study of patients with progressive idiopathic scoliosis.Objective-To determine the relative contributions of vertebral and disc wedging to the increase in Cobb angle during 3 phases of adolescent skeletal growth and maturation.Summary of Background Data-Both disc wedging and vertebral body wedging are found in progressive scoliosis, but their relative contribution to curve progression over time is unknown. Which occurs first is important for understanding how scoliosis progresses and for developing methods to halt progression. Previous studies have not properly identified maturity and provide conflicting results.Methods-Eighteen girls were followed through their adolescent growth spurt with serial spine and hand skeletal age radiographs. Each Cobb angle was divided into disc wedge angles and vertebral wedge angles. The corresponding hand radiographs provided a measure of maturity level, the Digital Skeletal Age (DSA). The disc versus bone contributions to the Cobb angle were then compared during 3 growth phases: prior to the growth spurt, during the growth spurt and after the growth spurt. Significance of relative changes was assessed with the Wilcoxon two-sided mean rank test.Results-Prior to the growth spurt, there was no difference in relative contributions of the disc and the bone (3° vs 0°, p=0.38) to curve progression. During the growth spurt, the mean disc component progressed significantly more than that of the vertebrae (15° vs 0°, p=0.0002). This reversed following the growth spurt with the vertebral component progressing more than the disc (10° vs 0°, p=0.01).Conclusion-Adolescent idiopathic scoliosis initially increases through disc wedging during the rapid growth spurt with progressive vertebral wedging occurring later.

Analysis of the cervical spine sagittal alignment in young idiopathic scoliosis: a morphological classification of 120 cases

“…Nevertheless, the effect of vertebrae or disc on coronal deformity in scoliosis is certain [17]. However, without biomechanical and histological evidence, it is not convincing to conclude a causal relationship.…”

The Etiologic Relevance of 3-D Pathoanatomy of Adolescent Idiopathic Scoliosis

“…In two-dimensional radiographic studies on AIS, contradictory findings have been reported on the individual contribution of the vertebral bodies, as compared to the discs, to the coronal deformity. [66][67][68][69][70][71][72][73][74][75] Because the spinal column in AIS, unlike the normal situation, is longer anteriorly than posteriorly, it has been hypothesized that AIS is the result of active anterior overgrowth of the vertebral bodies, or reduced posterior growth by posterior tethering. 60,61 Furthermore, disorders of bone metabolism have been suggested to play an etiological role.…”

Adolescent idiopathic scoliosis: current perspectives

“…The relative anterior spinal overgrowth results in buckling of the spine, and causes the coronal curvature and the vertebral rotation. 22,33 The thoracic hypokyphosis that frequently occurs in AIS is a factor supporting this theory. [24][25][26] The inhibition of posterior growth may be tethered by muscle, ligament, or the spinal cord.…”