Review Question - QID 675

The patient has a "chin-on-chest" deformity due to severe kyphosis from ankylosing spondylitis. The best surgical treatment for this would consist of posterior extension osteotomies followed by posterior spinal fusion with instrumentation.

Ankylosing spondylitis is a seronegative spondyloarthropathy that results in enthesopathy and syndesmophytes formation of the annulus fibrosus, which leads to ankylosed spine. Disease progression is typically associated with severe kyphosis leading to tremendous sagittal plane imbalances if left untreated. In severe cases, a chin-on-chest deformity can result in difficulties with social interactions, due to poor eye contact, and self-feeding. Surgical treatment involves posterior extension osteotomies to restore level gaze and improve sagittal plane balance.

Belanger et al. retrospectively reviewed 26 patients who underwent posterior extension osteotomy, with the average patient achieving 38 degrees of sagittal correction and 9 of 10 patients with preoperative neurological deficits achieving some degree of neurologic improvement. The authors strongly recommend rigid internal fixation to prevent catastrophic subluxation at the osteotomy site.

Simmons et al. describe the specifics of the surgical technique, recommending the extension osteotomy be performed at the C7-T1 junction due to various anatomic advantages. The vertebral vessels are anterior to the spine, the spinal canal is wider at this level, and the C8 nerve root tolerates migration better than nerve roots higher in the cervical spine.

Figure A shows a man with "chin-on-chest" deformity caused by increasing kyphosis at the cervicothoracic junction. Figure B is a sagittal CT scan of the cervical and upper thoracic spine demonstrating severe kyphosis. Figure C is an AP radiograph of the lumbar spine demonstrating a "bamboo spine" that is pathognomic for ankylosing spondylitis.

Incorrect Answers:
Answer 1: Anterior osteotomy is technically difficult and does not allow the necessary access to the C7 pedicle needed to achieve adequate sagittal correction.
Answer 2: Halo traction will not correct the severe kyphotic deformity.
Answer 3: Posterior fusion in situ may prevent further deformity but will not improve the patient's functional or neurologic status.
Answer 4: Anterior osteotomy does not allow resection of the C7 pedicle which is needed to achieve the needed sagittal correction.