RECOGNITION AND TREATMENT OF THE PROXIMAL THORACIC CURVE IN ADOLESCENT IDIOPATHIC SCOLIOSIS TREATED WITH COTREL-DUBOUSSET INSTRUMENTATION

Study Design. A retrospective radiographic and clinical review of a consecutive series of patients with adolescent idiopathic scoliosis (AIS) instrumented/fused with Cotrel-Dubousset instrumentation (CDI) was undertaken. Objective. The authors determined criteria when the upper thoracic curve should be instrumented/fused in AIS treated with CDI and assessed the results of surgical treatment. Summary of Background Data. Failure to recognize and include the upper left thoracic curve in the instrumentation/fusion of a lower right thoracic idiopathic scoliosis may produce shoulder imbalance and coronal decompensation. Patients with an elevated left shoulder clinically or a positive T1 tilt radiographically usually require instrumentation/fusion of the proximal thoracic curve. However, the upper left thoracic curve may be structural and require inclusion in the instrumentation/fusion when the shoulders clinically are level or even if the right shoulder is elevated preoperatively when using CDI. Methods. The authors compared 27 patients with AIS with structural upper thoracic curves that were instrumented with CDI to T2 (Group I) to 27 patients with King Type III curves treated with CDI that did not have the upper thoracic curve instrumented/fused (Group II). Results. The distinguishing Group I preoperative criteria indicating a structural upper thoracic curve included a proximal thoracic curve greater than 30-degrees that corrected to no better than 20-degrees on sidebending; greater-than-or-equal-to Grade I rotation or greater-than-or-equal-to 1 cm translation present at the apex of this curve; any elevation of the left shoulder or tilt of T1 into the concavity of the upper thoracic curve; or when the transitional vertebra between the two curves is at T6 or below. Conclusions. When these aforementioned criteria are present and surgical correction with CDI is planned, we recommend extending the instrumentation up to T2 to produce level shoulders and maintain coronal balance.