Complications of spinal osteotomy for thoracolumbar kyphosis secondary to ankylosing spondylitis in 342 patients: incidence and risk factors

OBJECTIVE To describe the incidence of complications in spinal osteotomy for thoracolumbar kyphosis caused by ankylosing spondylitis (AS) and to investigate the risk factors for these complications. METHODS From April 2000 to July 2017, 342 consecutive AS patients with a mean age (+/- SD) of 35.4 +/- 9.8 years (range 17-71 years) undergoing spinal osteotomy were enrolled. Patients with complications within the 1st postoperative year were identified. Demographic, radiological, and surgical data were compared between patients with and without complications. The complications were classified into intraoperative and postoperative complications. RESULTS A total of 310 consecutive pedicle subtraction osteotomy (PSO) and 37 multiple Smith-Petersen osteotomy (SPO) procedures were performed in 342 patients. Overall, 47 complications were identified in 47 patients (13.7%), including 31 intraoperative complications and 16 postoperative complications. Patients with complications were older than those without (p = 0.006). A significant difference was observed in preoperative global kyphosis (GK), lumbar lordosis (LL), sagittal vertical axis (SVA), and the correction of these radiographic parameters between patients with and without complications (p < 0.05). Two-level PSO (p = 0.022) and an increased number of instrumented vertebrae (p = 0.019) were significantly associated with an increased risk of complications. CONCLUSIONS The overall incidence of complications was 13.7%. Age; preoperative GK, LL, and SVA; the correction of GK, LL, and SVA; 2-level PSO; and number of instrumented vertebrae were risk factors. Therefore, the potential risk of extensive surgeries with large correction and long fusion in older AS patients with severe GK should be seriously considered in surgical decision-making.