Study DesignThe effect of spinal instrumentation in Idiopathic scoliosis was studied in 21 patients who had Harrington instrumentation and 15 who had Wisconsin Drummond instrumentation.ObjectiveRadiographs were analyzed to determine if the frontal and transverse plane shape of the scoliosis curve was changed by surgery, with and without segmental fixation.Summary of Background DataPrevious reports were based on frontal plane measurements of the curve (Cobb angle). The study reports correction in the frontal plans (Cobb angle) and transverse plane (apical vertebral rotation), as well as the regional distribution of the correction.MethodsRadiographs before surgery, soon after, and between 5 and 48 months after surgery were marked and digitized to measure the regional distribution of the frontal plane shape and transverse plane vertebral rotation.ResultsDespite improvement in the magnitude of the deformity, the scoliosis curbe shape remained almost constant postoperatively. There was minimal correction of the apical vertabra axial rotation in either group.ConclusionThis study documents that although the Harrington and Wisconsin-Drummond instrumentation systems decrease the Cobb angle, they do not change the shape of the curve or correct apical vertebra axial rotation. Newer instrumentation designs need to look beyond the Cobb angle as the only measure of outcome.
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