Changes in vertebral rotation after Harrington and Luque instrumentation for idiopathic scoliosis.

This study was carried out to analyze the three-dimensional and in particular the rotational correction obtained after spine instrumentation for idiopathic scoliosis. Preoperative and postoperative radiographs and computed tomographic scans with single axial cuts through each vertebral level were obtained for 14 patients: 4 Harrington, 7 Luque, and 3 Harrington-Luque. Rotation of vertebrae relative to the spinal axis and rotation between vertebrae (segmental rotation) were measured from computed tomographic scans of instrumented and uninstrumented segments. The derotation and changes occurring after surgery were calculated. Before operation, rotation was maximal at the apex, and close to 0 at the end vertebra; segmental rotation was greatest at the end of the curve, and minimal at the apex. After Harrington instrumentation the apical vertebrae showed a median derotation of 16%, after Luque instrumentation it was 12% and after Harrington-Luque instrumentation it was 13%. Segmental derotation did not uniformly occur. Major derotation was obtained at the end vertebrae and 39% of the total derotation occurred outside of the instrumented levels of the spine.