A Novel Stepwise Technique for Safe and Effective Transoral Release of Irreducible Atlantoaxial Dislocation: A Retrospective Study of 201 cases.

Abstract

Retrospective cohort study. To verify the clinical efficacy of a novel Transoral Stepwise Release Technique (TSRT) for treatment of irreducible atlantoaxial dislocations (IAAD). Anterior release for IAAD remains challenging, with 3.2 times higher complication rate than posterior release. However, there are some patients who cannot achieve successful reduction from a posterior approach, and require the higher-risk anterior release. Our work presents a novel anterior release technique that aims to minimize iatrogenic injury and associated complications from an anterior release. IAAD cases who were treated with TSRT were retrospectively studied. Primary outcomes included fusion rate, complications, and neurological function over the course of minimum one-year follow-up. Radiographic differences between preoperative and postoperative imaging were also considered. A preoperative prediction model for the actual release grade was developed using multivariate logistic regression based on demographic factors and the craniovertebral abnormalities identified on preoperative images, evaluating the need for higher-grade TSRT release. We included 201 IAAD cases, with 42% (84/201) demonstrating degeneration of the atlantoaxial joint or anterior-hook-like dens. Reduction was achieved in all cases, with 80% (160/201) of cases only requiring relatively low-grade (grade I) TSRT release. Degeneration of the atlantoaxial joint was significantly associated with the need for higher-grade TSRT release (OR 16.68, CI: 2.91-94.54, P=0.002). The overall complication rate was 4.5% (9/201). Over the course of follow-up, the fusion rate reached 98.5%, and the ASIA and JOA score were significantly improved to 97.28 and 16.25 (P<0.01 and P<0.01), respectively. This study demonstrated that our novel TSRT anterior release technique demonstrated complication rates similar to those published in the literature for posterior release. TSRT can be used as an alternative to posterior release techniques for refractory cases or when a posterior approach is not considered viable.