P107. Releasing anterior soft tissue and reduction of the irreducible atlantoaxial dislocation associated with basilar invagination through single-stage posterior approach

Abstract

BACKGROUND CONTEXT The management of AAD combined with BI is challenging. Traditional posterior approaches lack the ability to release the anterior soft tissue and result in unsatisfactory reduction; posterior fixation followed by the anterior release approach has higher morbidity and lead to higher costs and a longer length of stay. PURPOSE This study aims to analyze outcomes of the release of anterior soft tissue through posterior route in order to reduce irreducible atlantoaxial dislocation (AAD) and basilar invagination (BI) through a single-stage operation. This study aims to analyze outcomes of the release of anterior soft tissue through posterior route in order to reduce irreducible atlantoaxial dislocation (AAD) and basilar invagination (BI) through a single-stage operation. STUDY DESIGN/SETTING This is a retrospective study. PATIENT SAMPLE Thirty-one patients with irreducible AAD and concomitant BI with congenital osseous abnormalities were analyzed. OUTCOME MEASURES The clinical results were evaluated using the Japanese Orthopedic Association (JOA) scale, and the radiological measurements included anterior atlantodental interval (ADI), the distance of odontoid tip above Chamberlain line, clivus-canal angle (CCA) and the length of the syrinx. METHODS The anterior soft tissue was released posteriorly, and cages were placed into the facet joint followed by occipital-cervical fixation with cantilever correction. We used paired t-test to compare preoperative and postoperative measurements. RESULTS The mean JOA score increased from 11.65 to 14.48 at 1-year follow-up. Complete reduction of AAD and BI was achieved in 23 patients (74.2%). The mean clivus-canal angle improved from 113.0 degrees preoperatively to 148.4 degrees postoperatively. Shrinkage of the syrinx was observed in 6 patients in one week after surgery. Nine patients had 18-month follow-up and achieved bone fusion. Twenty-two patients have a 12-month follow-up, and 19 (86.3%) achieved bony fusion. Unilateral vertebral artery occlusion was diagnosed in 2 cases without clinical symptoms. CONCLUSIONS It appears effective and safe to treat irreducible AAD associated with BI by releasing the anterior soft tissue from a posterior approach. Cage implantation within the facet and fixation using cantilever can achieve complete reduction in most cases. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.