Enhanced capacity for spontaneous correction of lumbar curve in the treatment of major thoracic-compensatory C modifier lumbar curve pattern in idiopathic scoliosis

Study Design. Retrospective radiographic review. Objective. To evaluate the outcome of maximal selective thoracic correction with controllable corrective forces provided by cantilevel bending technique (CBT) for idiopathic scoliosis (IS) in the presence of widely deviated compensatory lumbar curve. Summary of Background Data. Current intraoperative instrumentation and fusion techniques for selective fusion involve undercorrection of the thoracic curve while allowing for spontaneous lumbar curve correction and maintaining overall coronal balance. Since the lumbar curve is nonstructural and compensatory, procedures for selective thoracic fusion should approximate the best possible correction of thoracic curve such that resultant spontaneous lumbar curve correction and compensation is maximized. Methods. Thirty-seven consecutive IS patients with main thoracic compensatory minor C modifier lumbar curves underwent maximal selective thoracic correction by CBT at a single institution. Radiographs were analyzed before surgery, immediately after surgery, and at most recent follow-up (range, 2-6 years). Results. A mean 83% thoracic correction was closely matched by a 81% lumbar correction at most recent follow-up. The mean thoracic curve correction/flexibility ratio was 2.4. Enhanced capacity for spontaneous correction of lumbar curve was evidenced by the mean correction/flexibility ratio of 1.2. Spontaneous correction of lumbar apical translation occurred in all patients. Global coronal imbalance was common before surgery (mean, 11 mm), and remained similarly so after surgery (mean, 12 mm). Conclusion. Use of CBT facilitates 3-dimensional control of corrective forces and allows for maximum selective instrumentation-assisted thoracic and spontaneous lumbar curve correction in patients with Lenke 1C or 2C IS.