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 repor ted; Objectives, To emphasize the disparate effect of osteotomy level on sagitta l balance and gaze angle in surgical correction of global kyphotic deformit y, and to describe a new surgical technique. Summary of Background Data. Previous reports of cervical osteotomy essentia lly have described extension osteotomy for correction of severe flexion def ormity. To the authors' knowledge, flexion osteotomy to correct extension d eformity of the cervical spine has not been described previously. Methods. A 44-year-old woman with global kyphotic deformity caused by ankyl osing spondylitis underwent corrective lumbar osteotomy at another institut ion. Ten years later, she experienced further development of the kyphosis, predominantly at the thoracic level, with resultant-restriction:ion of forw ard gaze; Thoracic corrective osteotomy was: per formed, 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-stag e, in the lateral decubitus. The use of transparent drapes permitted direct visualization of the chin-brow angle during operation. Anterior prate fixa tion prevented any translation at the osteotomy site. Results. The osteotomy united; the gaze angle was fully corrected (45 degre es to -30 degrees). No deterioration was noted at 2-year follow-up. Conclusions, Osteotomy at a higher level in the spine for correction of glo bal kyphotic deformity may result in a significant overcorrection of the ga ze angle upward. The authors believe that the new technique described in th is report is a technically demanding but adequate and safe approach for cor recting such a rare deformity.