Thoracic Hyperkyphosis: Assessment of the Distal Fusion Level

Study Design  This is a retrospective study. Objective  The objective of this study was to assess the sagittal stable vertebra (SSV) versus the first lordotic vertebra (FLV) as the inferior fusion level in patients undergoing spinal surgery for thoracic hyperkyphosis. The main outcome of interest was the development of distal junctional kyphosis (DJK). Summary of Background Data  Prior research has pointed to selection of the FLV for the distal instrumentation level in fusion for thoracic hyperkyphosis. In 2009, Cho et al introduced the concept of the SSV after recognizing the development of DJK despite fusion to the FLV. Methods  Patients were reviewed who had undergone spinal fusion for thoracic hyperkyphosis. Preoperative radiographs were reviewed to assess thoracic kyphosis, lumbar lordosis, SSV, and FLV. Postoperative radiographs were reviewed to assess curve correction and whether patients developed DJK or implant failure. Results  We reviewed 22 patients with a mean age at surgery of 18 (range 14 to 22). Mean preoperative kyphosis was 85 ± 14 degrees, and mean postoperative kyphosis at final follow-up was 59 ± 12 degrees for a mean correction of 26 ± 12 degrees. Eleven patients developed DJK and four patients experienced hardware failure. In 12 patients, the SSV was inferior to the FLV. Rates of DJK when the instrumentation included the SSV or FLV were 13 and 38%, respectively. Conclusions  Fusion to the SSV is superior at preventing DJK when compared with fusion to the FLV.