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The Reversibility of Swan Neck Deformity in Chronic Atlantoaxial Dislocations

Passias, Peter G. MD*; Wang, Shenglin MD; Zhao, Deng MD; Wang, Shaobai PhD; Kozanek, Michal MD; Wang, Chao MD

doi: 10.1097/BRS.0b013e31828625e4
Cervical Spine

Study Design. Prospective case series and radiographical analysis.

Objective. This study aimed to characterize the changes in subaxial alignment after surgical correction of occipitoaxial kyphosis, establish normal parameters, and report on clinical outcomes in a population of patients with chronic atlantoaxial dislocation patients presenting with swan neck deformities.

Summary of Background Data. Swan neck deformity of the cervical spine is a term used to describe the simultaneous development of both abnormal kyphosis and hyperlordosis malalignments. Currently, there are no published series that discuss their outcomes after treatment and, more specifically, the subsequent changes that occur in the subaxial spine after the correction of the primary deformity in cases of chronic hyperkyphosis at the occipitoaxial segment.

Methods. This was a prospective clinical and radiographical study in a population of patients with chronic atlantoaxial dislocation presenting with swan neck deformities. C0–C2 and C2–C7 angles were measured using plain radiographs pre- and postsurgery. The relationship between the alignment of the occipitoaxial joint and the subaxial cervical spine was evaluated. Japanese Orthopaedic Society scores were used to assess functional outcomes.

Results. C0–C2 improved from a mean of −14.4° (SD, 9.5°) preoperatively to a mean of 7.8° (SD, 1.0°) postoperatively (P = 0.02). C2–C7 changed from a mean of 43° (SD, 2.8°) to a mean of 18.6° (SD, 11.2°) postoperatively (P = 0.02). A significant correlation was detected between the changes that occurred in the upper and lower cervical alignments (R2 = 0.133; P < 0.01). Clinically, the Japanese Orthopaedic Society preoperative scores improved significantly to postoperative (P < 0.01).

Conclusion. This study reports the novel auto-correction of subaxial abnormalities after treatment of the primary upper cervical deformity and delineates the relationship between these 2 occurrences, thus demonstrating the reversibility of such complex abnormalities. Furthermore, the clinical outcomes after surgical treatment of swan neck deformities secondary to atlantoaxial dislocation are favorable and associated with a low complication rate.

Level of Evidence: 2

Swan neck deformity of the cervical spine is a term used to describe the simultaneous development of both abnormal kyphosis and hyperlordosis malalignments. This study reports the novel auto-correction of subaxial abnormalities after treatment of the primary upper cervical deformity and delineates the relationship between these 2 occurrences, thus demonstrating the reversibility of such complex abnormalities.

*Division of Spinal Surgery, NYU Medical Center/Hospital for Joint Diseases, NYU School of Medicine, New York, NY

Orthopaedic Department, Peking University Third Hospital, Beijing, China; and

Bioengineering Lab, Department of Orthopaedic Surgery, Massachusetts General Hospital/Harvard Medical School, Boston, MA.

Address correspondence and reprint requests to Chao Wang, MD, Orthopaedic Department, Peking University Third Hospital, 49 North Garden Street, Haidian District, Beijing, China 100191; E-mail: wangchaoo@ynet.com

Acknowledgment date: June 27, 2012. First revision date: October 13, 2012. Second revision date: December 22, 2012. Acceptance date: December 27, 2012.

The manuscript submitted does not contain information about medical device(s)/drug(s).

No funds were received in support of this work.

No relevant financial activities outside the submitted work.

© 2013 Lippincott Williams & Wilkins, Inc.