Selective thoracic fusion for adolescent idiopathic scoliosis with C modifier lumbar curves: 2- to 16-year radiographic and clinical results

Study Design. Retrospective clinical and radiographic review with functional outcome assessment. Objectives. To evaluate outcome of selective thoracic fusion for adolescent idiopathic scoliosis in the presence of widely deviated compensatory lumbar curves. Summary of Background Data. Previous reports on the results of selective thoracic scoliosis fusion have not specifically focused on deformities with widely deviated lumbar curves. Whether these challenging deformities are best treated with selective thoracic fusion or fusion of both curves remains unclear. Methods. Forty-four consecutive patients with adolescent idiopathic scoliosis with main thoracic, compensatory minor lumbar "C" modifier curves underwent selective thoracic fusion at a single institution (1987-2000). Radiographs were analyzed before surgery, at 1 week, 2 years, and latest follow-up (2-16 years; mean 5.0 years). Results. A mean 36% thoracic correction was closely matched by a 34% lumbar correction at latest follow-up. A majority of spontaneous lumbar correction occurred at its cephalad segments (P = 0.001). Spontaneous correction of lumbar apical translation occurred in a majority of patients ( prognostic factors identified). Global coronal imbalance (2-5 cm) was common before surgery and was a significant risk factor (P = 0.04) for global imbalance at latest follow-up. Postoperative bracing was not utilized, and there were no reoperations. Patients with coronal imbalance (2-5 cm) at latest follow-up had slightly inferior SRS-24 results. Conclusions. Satisfactory results are achieved with selective thoracic fusion of properly selected C modifier lumbar curves. Correction of the lumbar curve results principally from a decrease in the tilt of its upper vertebrae, but not necessarily improved apical translation. Mild coronal imbalance was well tolerated and has not necessitated distal extension of the fusion.