The change in back shape after Luque segmental sublam-inar instrumentation was assessed in the frontal, sagittal, and transverse planes in 61 patients with adolescent idiopathic scoliosis using the Integrated Shape Investigation System (ISIS) and standard radiographic techniques, Luque instrumentation was found to be an effective method of correcting thoracic and thoracolumbar curves in the frontal plane with a 59% and 63% respective reduction in the size of the preoperative Cobb angle. Despite the frontal plane correction, however, the ISIS scan showed that of the 40 single thoracic curves, the rib hump was reduced in only 6 patients, was unchanged in 27 patients, and was worsened slightly in 7 patients. By contrast, thoracolumbar and lumbar curves were corrected in all three planes with a significant cosmetic Improvement.