Broader Curve Criteria for Selective Thoracic Fusion

Study Design. Retrospective radiographic review. Objective. To evaluate the outcome of selective thoracic fusion (STF) by using cantilever bending technique (CBT) and the direct vertebral rotation (DVR) technique for major thoracic-compensatory lumbar (MTCL) curves selected by new curve criteria, which are broader than Lenke curve criteria for STF. Summary of Background Data. Surgical treatment of MTCL curves aims to maximize the number of MTCL curves that can be treated with STF and optimize instrumented thoracic and spontaneous lumbar correction. Comparing current guidelines for STF shows that the surgical technique utilized for STF may affect the curve criteria for MTCL curves for successful STF and thoracic and lumbar correction. Methods. Seventy-eight consecutive idiopathic scoliosis patients with major thoracic-compensatory "C" modifier lumbar curves who met the following three criteria: (1) main thoracic curve (MT) to compensatory lumbar curve (CL) ratios of Cobb magnitude and apical vertebral translation (AVT) greater than one; (2) MT/CL ratio of flexibility less than one; (3) Cobb magnitude of lumbar curve less than 35 degrees on side bending, were treated with STF by using CBT and DVR. Radiographs were analyzed before surgery, immediately after surgery, and at the most recent follow-up (range, 2-5 years). Results. All 78 MTCL curves were successfully treated with STF by using CBT and DVR. A mean 61% thoracic correction was matched by 55% lumbar correction at the most recent follow-up. Spontaneous correction of lumbar AVT occurred in all patients. Global coronal imbalance was common before surgery (mean, 14 mm) and remained so after surgery (mean, 12 mm). There were 49 MTCL curves that did not meet Lenke curve criteria for STF. All were successfully treated with STF by using CBT and DVR. Among these 49 MTCL curves, there were 14 Lenke 1C and 18 Lenke 2C curves with one or two, or all of MT/CL ratios of Cobb magnitude, AVT, and apical vertebral rotation of 1.2 or less, and 6 Lenke 3C and 11 Lenke 4C curves with the Cobb magnitude of residual lumbar curve on side bending between 25 degrees and 35 degrees. Conclusion. CBT and DVR can broaden the current curve criteria of MTCL curves for STF to have more MTCL curves treatable with STF and optimize instrumented thoracic and spontaneous lumbar correction. A more effective surgical technique can not only improve instrumented thoracic and spontaneous lumbar correction but also can broaden the MTCL curve criteria for STF to have more MTCL curves treatable with STF.