Transpedicular Bivertebrae Wedge Osteotomy and Discectomy in Lumbar Spine for Severe Ankylosing Spondylitis

Study Design: A prospective study was performed in 8 patients with severe ankylosing spondylitis. Objectives: To observe the feasibility, reliability, and complications of a method of transpedicular bivertebrae wedge osteotomy and discectomy to manage the sagittal plane deformity in ankylosing spondylitis with chin-brow vertical angles beyond 90 degrees. Summary of Background Data: In ankylosing spondylitis, the correction of sagittal plane deformity can be achieved by lengthening the anterior elements, shortening the posterior elements, or a combination of the 2. Neither Smith-Petersen osteotomy, nor pedicle subtraction osteotomy in 1 segment can achieve adequate correction for cases of severe ankylosing spondylitis kyphosis. Methods: From January 2003 to May 2007, 8 patients (3 males and 5 females) with severe ankylosing spondylitis in our institution underwent a single stage transpedicular bivertebrae wedge osteotomy and discectomy. The operation technique includes resection of the posterior elements of 2 adjacent vertebrae, resection of the inferior-posterior aspect of proximal vertebra, and the superior-posterior aspect of the distal vertebra, followed by posterior instrumentation with pedicle screws and spinal fusion. Preoperative and postoperative height, chin-brow vertical angle, sagittal balance, and sagittal Cobb angle of the vertebral osteotomy segment were documented. Intraoperative, postoperative, and general complications were registered. Results: The mean follow-up was 18.7 +/- 6.1 months (range: 14 to 54 mo). The mean duration of surgery was 236 minutes (range: 198 to 310 min), and the average volume of intraoperative blood loss was 2200 mL (range: 1600 to 3860 mL). The patients' height increased from 120.5 +/- 12.0 cm to 159.6 +/- 12.4 cm (P = 0.000). The mean chin-brow vertical angle was improved from 102.8 +/- 9.7 to 19.3 +/- 13.9 degrees (P = 0.000). The spinal sagittal Cobb angle of the vertebral osteotomy segment was corrected from kyphosis 38.6 +/- 16.5 degrees to lordosis 26.6 +/- 10.1 degrees (P = 0.000). One patient with the involvement of the cervical spine suffered an extension spinal fracture at C5/6 as the operating table was extended. Translation at the osteotomy site occurred in 1 patient during the correction. Fusion of the osteotomy was achieved in all patients, and no loosening or breakage of pedicle screws was found. Conclusions: In cases of severe ankylosing spondylitis kyphosis with chin-brow vertical angles beyond 90 degrees, a single stage transpedicular bivertebrae wedge osteotomy and discectomy is an effective corrected method of correction.