Use of hinged rods for controlled osteoclastic correction of a fixed cervical kyphotic deformity in ankylosing spondylitis

Cervical kyphosis in patients with ankylosing spondylitis (AS) can be severely disabling. Surgical treatment of this disorder is technically demanding, however, with a considerable risk of neurological and vascular injuries. The extension osteotomy is a well-described posterior treatment for this condition, but this approach presents the risk of acute subluxation and spinal column translation during the reduction. In this paper, the authors report the novel use of a hinged posterior cervical rod for controlled correction of cervical kyphosis. After sustaining a traumatic spinal fracture, a 57-year-old man with AS developed a delayed cervical flexion deformity. The patient was neurologically intact, but suffered from disabling impairment in horizontal gaze and activities of daily living, and from neck pain. The patient subsequently underwent surgical correction via a posterior cervical extension osteotomy at C7-T1 with manual extension of the neck for osteoclastic reduction of the cervical kyphosis. Controlled correction was performed by using a hinged rod affixed to posterior cervical and thoracic screws, allowing for free sagittal correction while restricting translational forces. Once the desired angle of correction was achieved, the hinge connector was locked, transforming the rod into a rigid device for permanent internal fixation. The use of hinged rods in cervical kyphosis correction provides a controlled method for reduction at the osteotomy site, decreasing the risk of neurological injury.