Posterior pedicle screw fixation to treat lower cervical fractures associated with ankylosing spondylitis: a retrospective study of 35 cases

Background: The most common site of fractures in patients with ankylosing spondylitis (AS) is the cervical spine, especially the lower cervical spine and cervicothoracic junction. The optimal treatment for cervical spine fractures secondary to AS is controversial. This study aimed to explore the effects of posterior pedicle screw fixation alone on fractures of the lower cervical spine in patients with AS. Methods: From January 2006 to January 2013, a total of 35 patients with AS and a lower cervical spine fracture were treated using only posterior cervical/thoracic pedicle screw fixation. In this retrospective study, we reviewed the patients' charts to assess their case histories, operations, neurological outcomes, and complications. We also evaluated their postoperative radiographs to determine the time of bone fusion. Results: Altogether, 32 (91.4%) of the 35 fractures resulted from an acute injury and 3 (8.6%) from a chronic injury. In 25 cases, the fracture resulted from a low-energy spinal injury and in 8 cases from a high-energy injury. Posterior pedicle screw fixation was successful in all patients, with radiographic fusion confirmed by computed tomography. The average time of bone fusion was 3.6 months (range 3 - 6 months). The surgery improved the American Spinal Injury Association grade in 15 (42.9%) patients. No intraoperative complications occurred. None of the corrections resulted in neurological decompensation. The average postoperative correction was 18 degrees. Conclusions: Pedicle screw fixation and autologous bone grafting through a single posterior approach to lower cervical spine fractures in AS patients could stabilize the spine, correct kyphosis, and relieve pressure. It is thus reasonable to recommend this surgical strategy for AS-associated fractures of the lower cervical spine.