The rib-vertebra angles on the convexity and concavity of the spinal curve in infantile idiopathic scoliosis.

The components of Mehta's empirical rib-vertebra angle difference (RVAD) were observed as indicators of the prognosis in infantile idiopathic scoliosis (IIS). The following components were investigated in a retrospective study of 169 children with IIS: (1) convex rib-vertebra angle (RVA); (2) concave RVA; (3) RVAD; (4) initial spinal curve angle; and (5) age at diagnosis. The convex RVA, but not the concave RVA, was found to correlate significantly with the initial spinal curve angle. This is consistent with the hypothesis that factors that determine spinal curve progression in IIS are related to those that lead to drooping of the ribs on the convexity of the thoracic spinal curve. In terms of prognosis, the convex RVA, which entailed one measurement, was as accurate as the RVAD, which entailed two measurements and a calculation. A convex RVA of less than 68 degrees on the initial radiograph usually indicates that a spinal curve will progress.