Posterior osteotomy for thoracolumbar stress fracture in ankylosing spondylitis through the gap of a pathological fracture

Abstract

To evaluate the effectivity and safety of posterior osteotomy for thoracolumbar stress fracture in ankylosing spondylitis (AS) through the gap of a pathological fracture. Between April 2012 and August 2015, 8 patients with AS combined with thoracolumbar stress fracture were treated with posterior osteotomy through the gap of a pathological fracture to correct the kyphosis. There were 7 males and 1 female, with an average age of 51 years (range, 37-74 years). The history of AS was 1-40 years (mean, 21.7 years) and disease duration of stress fracture was 2-60 months (mean, 18.5 months). The segmental lesions included T 8, 9 in 1 case, T 10, 11 in 2 cases, T 11 in 2 cases, T 12, L 1 in 1 case, L 1, 2 in 1 case, and L 2, 3 in 1 case. The nerve function before operation according to Frankel grading was grade D in 3 cases and grade E in 5 cases. The pre- and post-operative X-ray films, CT three-dimensional reconstruction, and MRI were collected to measure the global kyphosis (GK), local kyphosis (LK), angle of the fusion levels (AFL), pelvic incidence (PI), pelvic tilt (PT), and sagittal vertical axis (SVA). Visual analogue scale (VAS) score was used to assess the back pain intensity. The operation time was 210-320 minutes (mean, 267 minutes), and the intraoperative blood loss was 400-2 000 mL (mean, 963 mL). Cerebrospinal fluid leakage was found in 3 patients, and the wound healed by removal of drainage tube and suturing drainage outlet after 5-7 days of operation. The wounds of the rest patients healed by first intention. Lower extremity numbness occurred in 1 case and recovered after 1 month of postoperative administration of oral mecobalamin. All the patients were followed up 20-43 months (mean, 28.4 months). No internal fixator loosening, fracture, and other complications occurred. All the fractures healed with the healing time of 3-12 months (mean, 6.8 months). At 3 months after operation, 3 cases with spinal cord injury of preoperative Frankel grade D recovered to grade E. The GK, LK, AFL, PI, PT, SVA, and VAS scores at 1 week after operation and at last follow-up were significantly improved when compared with preoperative ones ( P<0.05). Except for VAS score at last follow-up was significantly improved when compared with that at 1 week after operation ( P<0.05), there was no significant difference in the other indexes between at 1 week after operation and at last follow-up ( P>0.05). Posterior osteotomy through the gap of a pathological fracture is a safe and effective surgical procedure for kyphosis correction and relief of back pain in AS patients combined with thoracolumbar stress fracture. Successful bony fusion and good clinical outcomes can also be achieved by this surgical procedure.