Flexion osteotomy of the cervical spine: a new technique for correction of iatrogenic extension deformity in ankylosing spondylitis.

STUDY DESIGN A new surgical technique of cervical osteotomy to correct an extension deformity of the cervical spine is described, and a case is reported. OBJECTIVES To emphasize the disparate effect of osteotomy level on sagittal balance and gaze angle in surgical correction of global kyphotic deformity, and to describe a new surgical technique. SUMMARY OF BACKGROUND DATA Previous reports of cervical osteotomy essentially have described extension osteotomy for correction of severe flexion deformity. To the authors' knowledge, flexion osteotomy to correct extension deformity of the cervical spine has not been described previously. METHODS A 44-year-old woman with global kyphotic deformity caused by ankylosing spondylitis underwent corrective lumbar osteotomy at another institution. Ten years later, she experienced further development of the kyphosis, predominantly at the thoracic level, with resultant restriction of forward gaze. Thoracic corrective osteotomy was performed, which resulted in an upward deviation of her visual field. A flexion osteotomy was performed at C7-T1, using two separate posterior and anterior approaches, in one-stage, in the lateral decubitus. The use of transparent drapes permitted direct visualization of the chin-brow angle during operation. Anterior plate fixation prevented any translation at the osteotomy site. RESULTS The osteotomy united; the gaze angle was fully corrected (45 degrees to -30 degrees ). No deterioration was noted at 2-year follow-up. CONCLUSIONS Osteotomy at a higher level in the spine for correction of global kyphotic deformity may result in a significant overcorrection of the gaze angle upward. The authors believe that the new technique described in this report is a technically demanding but adequate and safe approach for correcting such a rare deformity.