title: Modified technique of transoral release in one-stage anterior release and posterior reduction for irreducible atlantoaxial dislocation.
abstract: BACKGROUND
  One-stage anterior release and posterior reduction is one of the most effective methods for irreducible atlantoaxial dislocation. However, the criteria of appropriate tissue release for successful posterior reduction is yet to be confirmed. Hence, an assistant technique using the transoral approach to verify satisfactory release is required. To evaluate the efficacy of the modified technique of transoral release for irreducible atlantoaxial dislocation (IAAD) with patients underwent one-stage anterior release and posterior reduction.
  
  
  METHODS
  Between January 2009 and June 2014, 23 consecutive patients diagnosed with IAAD free from bony union between the C1-C2 facet joints on reconstructive computed tomography scan underwent one-stage anterior release and posterior reduction after no response to 2 weeks of skull traction. During transoral release, an elevator was used as a lever repeatedly to confirm a 3-5 mm bilateral joint space between the lateral masses of the atlas and axis. The release was accomplished since a 3-5 mm joint space was achieved. After anterior release, posterior reduction and instrumented fusion were subsequently performed.
  
  
  RESULTS
  All patients were observed for an average of 18 (range 6-50) months. Nineteen of 23 patients achieved complete reduction while four had an incomplete reduction. Significant differences in pre- and postoperative JOA scores and cervicomedullary angle (CMA) were found. Twenty-one patients presenting with myelopathy had a JOA score of 12.9 at final follow-up, improved from 7.8 before surgery. The mean CMA improved to 143.5° postoperatively from 101.8° preoperatively. Bony fusion was confirmed in all cases under radiologic assessment during follow-up; there were no instrument failures.
  
  
  CONCLUSIONS
  The modified technique of transoral release provides appropriate criteria for anterior release, to achieve good posterior reduction without excessive tissue release or intraspinal manipulation, proving its value as an assistant technique in one-stage anterior release and posterior reduction for IAAD.
authors.affiliation: Graduate School of Peking Union Medical College, 100005, Beijing, China; Department of Spine Surgery, China-Japan Friendship Hospital, 100029, Beijing, China.
authors.forename: Haoning
authors.initials: H
authors.lastname: Ma
authors.affiliation: Graduate School of Peking Union Medical College, 100005, Beijing, China; Department of Spine Surgery, China-Japan Friendship Hospital, 100029, Beijing, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Dong
authors.affiliation: Department of Spine Surgery, China-Japan Friendship Hospital, 100029, Beijing, China; Graduate School of Beijing University of Chinese Medicine, 100029, Beijing, China.
authors.forename: Chuyin
authors.initials: C
authors.lastname: Liu
authors.affiliation: Department of Spine Surgery, China-Japan Friendship Hospital, 100029, Beijing, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Yi
authors.affiliation: Department of Spine Surgery, China-Japan Friendship Hospital, 100029, Beijing, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Yang
authors.affiliation: Department of Spine Surgery, China-Japan Friendship Hospital, 100029, Beijing, China.
authors.forename: Xiangsheng
authors.initials: X
authors.lastname: Tang
authors.affiliation: Graduate School of Peking Union Medical College, 100005, Beijing, China; Department of Spine Surgery, China-Japan Friendship Hospital, 100029, Beijing, China. Electronic address: zrtanms@sina.com.
authors.forename: Mingsheng
authors.initials: M
authors.lastname: Tan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001268:Atlanto-Axial Joint / Q000293:injuries*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D004204:Joint Dislocations / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009055:Mouth; D019637:Orthopedic Procedures / Q000379:methods*; D012189:Retrospective Studies; D055815:Young Adult