Surgical correction of vertebral axial rotation in adolescent idiopathic scoliosis: Prediction by lateral bending films

The pre- and postoperative radiographs of 45 patients with scoliosis were compared with the preoperative lateral bending radiographs. The purpose was to compare correction of Cobb angle and apical vertebral rotation between preoperative lateral bending and operative spinal instrumentation. Twenty- one patients had Harrington instrumentation, 12 had Drummond/Wisconsin spinous process segmental instrumentation, and 12 had Texas Scottish Rite Hospital instrumentation. From the pre- and post-operative radiographs, each vertebra was marked and digitized for computerized measurements of Cobb angle and apical vertebral rotation. Correction of Cobb angle on the lateral bending radiograph averaged 22 ± 10°, which was less than that achieved at operation (Harrington 23 ± 7°, Drummond/Wisconsin 29 ± 10°, and Texas Scottish Rite Hospital 36 ± 6°; p < 0.01, paired t test). In contrast, correction of apical vertebral rotation on the lateral bending radiograph averaged 4 ± 8°, which was not significantly different from that achieved at operation (Harrington 1 ± 8°, Drummond/Wisconsin 1 ± 7°, and Texas Scottish Rite Hospital 4 ± 8°). Spinal instrumentation markedly corrected the Cobb angle but minimally corrected apical vertebral rotation. In contrast, preoperative lateral bending produced a similar proportional correction of both.