Results of closing wedge osteotomy in the treatment of sagittal imbalance due to ankylosing spondylitis

Objective: Ankylosing spondylitis is a systemic disease which affects the axial skeleton and may cause rigid spinal deformities in advanced cases. Clinical and radiological results of patients with ankylosing spondylitis who underwent pedicle subtraction osteotomy (PSO) were evaluated. Methods: Twelve (3 female, 9 male) patients who were treated for rigid spinal deformities due to ankylosing spondylitis were evaluated. All patients were treated with the same surgical technique, which included PSO and pedicle screw-rod combination. For radiological results, thoracic kyphosis, lumbar lordosis, pelvic parameters (pelvic incidence, sacral inclination, pelvic tilt), and the distance between the central sagittal line (CSVL) and the sacrum were measured from pre- and postoperative radiograms. For functional results, SF-36 and Oswestry Disability Index (ODI) were used. Results: Mean age of the patients was 39.8 +/- 8.4 years, and mean follow-up was 85.6 +/- 39.1 months. Mean angle of lordosis was improved from 6.6 degrees +/- 13.7 degrees preoperatively to 43.8 degrees +/- 8.4 degrees postoperatively (p<0.0001). Mean CSVL was improved from 19.7 +/- 9.7 cm preoperatively to 7.45 +/- 3.8 cm postoperatively (p=0.0005). Mean local angular change around the osteotomy site was 30.2 degrees +/- 6.2 degrees. The pelvic parameters were not significantly changed after the surgeries. Mean ODI, SF-36 mental, and SF-36 physical scores were 30.16 +/- 9.7, 41.2 +/- 9.9 and 35.3 +/- 7.1, respectively. Conclusion: In patients with rigid sagittal spinal deformities due to ankylosing spondylitis, lumbar lordosis and sagittal balance can be obtained using PSO.