Operative strategies for atlanto-axial dislocation revision surgery

English Keywords:Atlantoaxial dislocation  Revision surgery  Operative strategies

English Abstract:

  【Abstract】 Objectives: To explore the operative strategies of revision surgery after atlanto-axial dislocation(AAD) surgery. Methods: 12 patients undergone AAD revision surgery in our hospital between January 2016 and August 2019 were analyzed in this retrospective study, including 3 males and 9 females, aged 7-62 years[45.5(34.25, 52.50) years]. The interval of initial operation and revision operation was 3-360 months[30(5, 93) months]. Internal fixation and bone graft were removed before revision surgery. The patients were assessed to receive anterior release according to the conditions of 1/6 body weight dose skull traction. According to preoperative imaging and intraoperative exploration, larger diameter and longer screws, new screw track, and extended fixed segments were performed optionally to increase the overall internal fixation strength, and the lateral atlantoaxial joint release and grafting were performed to increase bone graft fusion. The follow-up period ranged 12-50 months [24.0(17.25, 34.00)months]. The atlanto-dental interval(ADI), clivus-axial angle(CAA), cervico-medullary angle(CMA) and Japanese Orthopaedic Association(JOA) score were assessed at 3 days after surgery and final follow-up, the CT examination was performed at 3 days, 3 months, 6 months, 12months and final follow-up after surgery to evaluate the bone graft fusion. Results: There were 8 patients receiving internal fixation and bone graft removing before revision surgery. Among the patients, 4 received anterior releasing combined with posterior reduction and internal fixation and fusion, the other 8 patients underwent posterior reduction and internal fixation and fusion. Of all the patients, occipital screw revision was performed in 4 with new screw track; C1 screw revision was performed in 4, of which 2 patients were fixed with larger diameter and longer screws, and 2 patients were fixed with new screw track; C2 screw revision was performed in 8, of which 5 patients were fixed with larger diameter and longer screws, and 3 patients were fixed with new screw track; extended fixed segments were preformed in 3 patients; the lateral atlantoaxial bone grafting was performed in all 12 patients. Anatomical reduction was obtained in all the patients. The postoperative 3d and final follow-up ADI were significantly reduced compared with pre-operative ADI, and the CCA and CMA were significantly increased than those at pre-operation(P<0.05). The JOA at 3 days after surgery and final follow-up were significantly improved than that at pre-operation. Bony fusion was achieved in all the patients, with a bone fusion rate of 100%, and the bone fusion time ranged 3-7 months[3.5(3.0, 6.0) months]. Conclusions: Anterior release is suitable for the patients with un-reduced atlantoaxial dislocation after removal of primary internal fixation under heavy traction. During posterior revision surgery, occipital screws need to change trajectory to maintain firm internal fixation, and larger diameter and longer screw is suitable for C1, and C2 screws, while extended fixed segments are suitable for patients whose C1 or C2 screws cannot be inserted. The lateral atlantoaxial joint bone grafting is suitable for all AAD revision.