Is Decompensation Preoperatively a Risk in Lenke 1C Curves?

Study Design. A review of a multicenter, prospective registry of patients surgically treated for adolescent idiopathic scoliosis. Objective. To investigate preoperative and postoperative distribution of coronal decompensation in Lenke 1C curves and to determine whether a selective thoracic fusion (STF) affects the results of coronal decompensation. Summary of Background Data. Numerous causes of postoperative coronal decompensation in Lenke 1C curves have been reported; however, there are few reports focusing on preoperative decompensation and its relation to postoperative decompensation in Lenke 1C curves. Methods. Patients with Lenke 1C prospectively collected from a multicenter study were analyzed. Preoperatively, patients were grouped as decompensated (C7-CSVL > 2 cm) or balanced (C7-CSVL within 2 cm, where CSVL is central sacral vertical line). Preoperative distribution and factors for postoperative coronal decompensation were investigated. Results. Seventy-one patients (53 STF, 18 nonselective fusions) were included. Preoperatively, coronal balance was skewed to the left (-17 +/- 13 mm). Of the 21 STF decompensated to the left preoperatively, 12 (57%) remained to the left at 2 years. Postoperative thoracic correction was significantly better in those balanced postoperatively (57%) compared with those who remained decompensated (46%; P < 0.05). There were 32 STF patients who were balanced preoperatively, with 10 of these (31%) decompensated to the left at 2-year follow-up. This rate (31%) was significantly less than the group that was decompensated preoperatively (57%, P = 0.04). In the nonselective fusion group, 16 out of 18 patients (89%) were balanced at 2-year follow-up, independent of preoperative balance. Conclusion. Patients with Lenke 1C tended to be decompensated to the left preoperatively. In those decompensated preoperatively who underwent a STF, the majority remained greater than 2 cm to the left at 2-year follow-up. Patients with both thoracic and lumbar curves fused had better coronal balance at 2 years than selectively treated patients. Although not a contraindication to performing a selective fusion, treating surgeons should be prepared for modest coronal decompensation in 40% of patients with Lenke 1C treated with selective fusion of the thoracic curve alone.