The selection of fusion levels using torsional correction techniques in the surgical treatment of idiopathic scoliosis

Study Design. This is a retrospective, consecutive case series, with the in dex patient included. Objectives. To evaluate the evolution and effectiveness of instrumentation techniques designed to untwist the scoliosis deformity. Summary of Background Data. Three-dimensional studies of the idiopathic sco liosis deformity are consistent with the theory that the deformity or defor mities evolve as an imperfect torsion or torsions. Methods. From 1989 through 1995, 102 consecutive patients (84 females, 18 m ales) underwent surgery with increasing emphasis on torsional correction. O ne hundred patients (98%), with an average age of 14.3 years (range, 10.5-2 0.8 years), were observed for an average of 40 months (range, 24-81 months) . The upper instrumented vertebra evolved to be the centered vertebra. The lower instrumented vertebra was chosen based on its ability to become horiz ontal on contralateral bend radiographs and was termed the caudal foundatio n vertebra. Because these techniques evolved over the first 3 years of the study period, a split analysis was performed to evaluate improvements in co rrection and correction maintenance over the course of the study. Results. The average Cobb angle was 59 degrees before surgery, 18 degrees a fter surgery (69% correction), and 22 degrees (63% correction) at latest fo llow-up. A comparison of the first half of the series with the second half showed no significant demographic differences. Curve correction was signifi cantly improved for King-Moe IIB (thoracolumbar-lumbar curve only), King-Mo e III, and King-Moe V curve types in the second half of the series. In the last 4 years, curve correction at latest follow-up for King-Moe IIB curves was 61% for the thoracic curve and 65% for the thoracolumbar-lumbar curve. King-Moe III curves had a 68% correction, and King-Moe V curves had a 50% h igh thoracic and a 72% thoracic curve correction. Thoracolumbar, lumbar, an d King-Moe I curves averaged 81% correction of the thoracolumbar-lumbar cur ve. The angle of thoracic curve inclination improvement at 1 year was maint ained at latest follow-up. Conclusions. This method of selecting instrumentation levels while using to rsional correction techniques is safe and reliable. The results were improv ed with the evolution of these techniques and appear to provide improved co rrection and correction maintenance compared with that of historical contro ls.