CHANGES IN SHAPE OF THE ADOLESCENT IDIOPATHIC SCOLIOSIS CURVE AFTER SURGICAL-CORRECTION

Study Design. The effect of spinal instrumentation in idiopathic scoli osis was studied in 21 patients who had Harrington instrumentation and 15 who had Wisconsin-Drummond instrumentation. Objective. Radiographs were analyzed to determine if the frontal and transverse plane shape of the scoliosis curve was changed by surgery, with and without segmen tal fixation. Summary of Background Data. Previous reports were based on frontal plane measurements of the curve (Cobb angle). The study rep orts correction in the frontal plane (Cobb angle) and transverse plane (apical vertebral rotation), as well as the regional distribution of the correction. Methods. Radiographs before surgery, soon after, and b etween 5 and 48 months after surgery were marked and digitized to meas ure the regional distribution of the frontal plane shape and transvers e plane vertebral rotation. Results. Despite improvement in the magnit ude of the deformity, the scoliosis curve shape remained almost consta nt postoperatively. There was minimal correction of the apical vertebr a axial rotation in either group. Conclusion. This study documents tha t although the Harrington and Wisconsin-Drummond instrumentation syste ms decrease the Cobb angle, they do not change the shape of the curve or correct apical vertebra axial rotation. Newer instrumentation desig ns need to look beyond the Cobb angle as the only measure of outcome.