Measurement variations in scoliotic angle, vertebral rotation, vertebral body height, and intervertebral disc space height.

Thirty consecutive posteroanterior and lateral radiographs of patients with adolescent idiopathic scoliosis with a mean Cobb angle of 24.4 degrees were read. In measuring the scoliotic angle, the interobserver error (SD) was 2.8 degrees and the intraobserver, 1.8 degrees. Rotation of the apical vertebra was estimated by measuring the translation of the pedicle on posteroanterior radiographs. For vertebral rotation, the interobserver measurement error (SD) was 3.4 and the intraobserver, 1.8%. The height of the apical vertebral body and the intervertebral disc space next inferior to it were measured on lateral radiographs as the anterior angles of the diagonals of the respective body or disc space. In measuring the vertebral body height, the interobserver error (SD) was 3.2 and the intraobserver, 2.6 degrees, and in measuring the intervertebral disc space height, the interobserver error was 2.4 and the intraobserver, 1.8 degrees. The angles can be transformed to a corresponding height/length ratio by a simple trigonometrical formula.