Abstract
Background: Adolescent idiopathic scoliosis has been intensively studied, but is still not understood. It is the paradoxical co-existence of rude health and gross deformity in the same individual that needs to be explained. The essence of scoliosis is asymmetry, and bilateral asymmetries in many anatomical features have been described in association with it. Measurement of asymmetry in back surface made possible by surface topography can explore this aspect and throw light on the evolution of the deformity as the Cobb angle changes.
Objective: To quantify the asymmetry of the back surface in scoliosis and the lesser non-scoliosis deformities.
Methods: Routine clinical material (patient demographics, radiography and surface topography) was analysed. Changes in body symmetry were quantified, using a topographic measure that calculates the difference, in three dimensions and at three levels, between the left and right sides of the back across the mid-line (natal cleft to first thoracic vertebra). Girls only (to eliminate any effect from sexual dimorphism) with all presenting degrees of deformity from barely failing the forward bend test through mild scoliosis unconfirmed by radiograph (Group 1, N=311) to documented scoliosis (Cobb angle => 10°), apex at T12 or below (Group 2 and apex above T12 (Group 3).
Results: All groups showed significant departures from bilateral symmetry. Groups 1 and 2 were similar, in that the left side was taller but narrower than the left. In Group 3, the side of curve convexity was taller than the concave side. This was reversed in left thoracic scoliosis patterns and was seen to increase over time with progression of the Cobb angle.
Discussion: It has long been acknowledged that scoliosis and growth are inseparable, but studies have failed to demonstrate a disease process or endocrine imbalance. These findings suggest that it is not a disorder superimposed on growth, but that growth itself causes the deformity. The spine, the whole trunk, in fact, is crooked because it grew that way. Only a small discrepancy in left-right symmetry is sufficient, over time and during periods of rapid growth, to produce both the curve and the rotation.
Conclusion: Scoliosis is neither a disease nor a mechanically induced aberration. It results from asymmetrical growth, which occurs at the cellular and molecular level.
Correspondence should be addressed to: Dr Caroline Goldberg, The Research Centre, Our Lady’s Children’s Hospital Crumlin, Dublin 12, Ireland.
