Reoperation depending on time period following pedicle subtraction osteotomy for thoracolumbar kyphosis in patients with ankylosing spondylitis

OBJECTIVE The aim of this study was to investigate time-dependent rates and indications of unplanned reoperation and to evaluate the most common indication depending on the time interval after pedicle subtraction osteotomy (PSO) for correction of thoracolumbar kyphosis in patients with ankylosing spondylitis (AS). METHODS A total of 321 consecutive patients with AS (284 men; mean age 43.8 years) with thoracolumbar kyphosis who underwent PSO were included. Patients who underwent reoperation after the index surgery were divided according to the duration of the follow-up period. RESULTS A total of 51 patients (15.9%) underwent unplanned reoperations. The reoperation groups had greater preoperative and postoperative C7 sagittal vertical axis (SVA), and less lordotic postoperative osteotomy angle (-4.3 degrees +/- 18.6 degrees vs -15.0 degrees +/- 13.7 degrees, p < 0.001). The perioperative change in SVA was not significantly different between groups (-10.0 +/- 7.1 cm vs -10.0 +/- 5.1 cm, p = 0.970), while that in the osteotomy angle was significantly different (-22.4 degrees +/- 21.3 degrees vs -30.0 degrees +/- 11.5 degrees, p = 0.014). Most reoperations (45.1%; 23/51) were performed within 2 weeks of the initial operation. Within 2 weeks, the most common cause of reoperation was neurological deficit in 10 patients, with a cumulative reoperation rate of 3.2%. After 3 years, the most common complications were mechanical complications in 8 patients, accounting for 15.7% (8/51) of patients. Overall, the most common indications for reoperation were mechanical complications (17 patients; 5.3%), followed by neurological deficits (12 patients; 3.7%). CONCLUSIONS PSO may be the most effective surgical procedure for the correction of thoracolumbar kyphosis in patients with AS. However, 51 patients (15.9%) required an unplanned reoperation.