Corrective Osteotomy in Ankylosing Spondylitis - Long-term Outcome and Complications

Study design: Retrospective and prospective outcome study of surgically treated ankylosing spodylitis cases for kyphosis.

Purpose: to record the long-term outcome and complications.

Materials and Methods: Sixteen cases of ankylosing spondylitis with global kyphotic deformity, who had corrective osteotomy of the spine between 1992 and 1998, were reviewed. Loss of forward gaze and/or loss of sagittal balance with progressive back pain were the indications for surgery.

Twelve cases had lumbar decancellation closing wedge osteotomy with pedicle subtraction. Three cases had additional cervical osteotomy and one case had thoracic osteotomy, following previous lumbar osteotomies. There were 10 male and 6 female patients and mean age was 52 years (range 40-72).

Results: Mean follow-up was 6.5 years (range 4-10). Preoperative mean sagittal imbalance (sagittal vertical axis, SVA) was 12 cm (range 4 - 29). Mean global kyphosis was 78 degrees (range 40-90). Spinal cord monitoring was routinely used.

Post-operatively, all the patients had improved sagittal balance. The mean SVA was 4.5 cm (range 3.5-8) in immediate post-operative period, and 6.2 cm (4.5-10) at final follo-up. The mean post-operative lumbar lordosis was 45 degrees, which deteriorated to 32 degrees at final follow-up. All cases had satisfactory correction of the visual angle.

One patient died intraoperatively due to excessive bleeding. Other immediate complications include superficial wound infection (3), dural tears (4), pulmonary complications (4). Long-term complications include two cases developed incomplete neurological deficit in the postoperative period, which partially recovered with conservative treatment. 12 cases required reoperation due to hardware failure and oseudarthrosis (6), deep infection (2), proximal junctional kyphosis (2), distal junctional kyphosis (1) and overcorrection of the kyphotic deformity requiring flexion osteotomy of the cervical spine in one case.

Despite significant complication rate, patient satisfaction was high in all the cases except one. All the fifteen cases expressed to have the procedure again. All of them had significant improvement in their sagittal balance, gaze angle, and quality of life.

Conclusion: Spinal osteotomy in ankylosing spondylitis is a difficult but rewarding procedure. Cord monitoring is mandatory. Immediate complications are frequent but patient satisfaction is high. The avoid long-term complications, and achieve a stable correction of both sagittal balance and visual angle, careful planning of the osteotomy site and instrumentation are the key factor.