Comparison of the clinical outcomes of two revision surgeries in cases of insufficient posterior atlantoaxial reduction

English Keywords:Revision surgery  Posterior approach operation for atlantoaxial dislocation  Transoral release of bony dislocation

English Abstract:

  【Abstract】 Objectives: To study the clinical effects of patients with irreducible atlantoaxial dislocation(IAAD) undergoing revision surgery due to insufficient atlantoaxial reduction. Methods: The clinical data of patients who underwent revision surgery due to nerve compression symptoms caused by insufficient atlantoaxial reduction from April 2000 to August 2021 were retrospectively analyzed. The patients were divided into two groups according to different revision surgery types: group A(transoral odontoid resection) and group B(posterior internal fixation removal and bone graft osteotomy, then anterior transoral atlantoaxial release and reduction, followed by posterior fixation and fusion, namely the "posterior-anterior-posterior" combined approach operation). The changes of spinal cord functions after operation were studied, and length of hospital stay, operative time, intraoperative bleeding, and complications were recorded, as well as preoperative and postoperative cervicomedullary angles(CMA). Japanese Orthopaedic Association(JOA) score was used for evaluating spinal cord function, and the improvement rate of spinal cord function(JOA improvement rate)=[(After treatment JOA score-Before treatment JOA score)/(17-Before treatment JOA score)]×100%. CMA improvement rate was used to describe the imaging improvement of atlantoaxial dislocation[CMA improvement rate=(Postoperative CMA-Preoperative CMA)/Preoperative CMA×100%], and it was compared between the two groups. Results: All 32 IAAD patients who underwent revision surgery due to insufficient atlantoaxial reduction had myelopathy before surgery, including 14 cases in group A and 18 cases in group B. In group A, the preoperative JOA score was 13.00±1.96, which was 15.54±1.08 at the final follow-up; The preoperative CMA was 132.66°±9.36°, and the final follow-up CMA was 144.74°±11.18°; The length of hospital stay was 21.93±14.07d, the operative time was 211.43±92.64mins, and the intraoperative blood loss was 279.29±345.17mL. In group B, the preoperative JOA score was 11.78±3.23, the final follow-up JOA score was 14.97±1.47; The preoperative CMA was 126.28°±11.06°, the final follow-up CMA was 154.71°±6.50°; The length of hospital stay was 35.83±26.19d, and the operative time was 368.83±118.55mins, and the intraoperative blood loss was 534.50±324.66mL. The complication rate of revision surgery in group A was 57.1%, the JOA improvement rate was (68.00±15.16)%, and the CMA improvement rate was (9.23±6.23)%. The revision surgery complication rate in group B was 33.3%, the JOA improvement rate was (63.59±10.89)%, and the CMA improvement rate was (23.21±9.83)%. The operative time and intraoperative blood loss in group A were significantly less than those in group B, and there was no significant difference in length of hospital stays between the two groups. The improvement rate of CMA in group B was significantly better than that in group A, while there was no significant difference in the rate of improvement in myelopathy(JOA score improvement rate) and complication rate of revision surgery between the two groups. Conclusions: Cases with insufficient atlantoaxial reduction of IAAD have higher rate of revision surgery complications and poorer clinical outcomes. Compared with transoral odontoid resection, the CMA improvement rate of the "posterior-anterior-posterior" combined approach surgery is better, and its biggest advantage is that it can completely restore the cervical spine force line while relieving spinal cord compression. The initial operation should be done with atlantoaxial anatomical reduction, and fixed fusion should be avoided as much as possible in the state of insufficient atlantoaxial reduction.