INTRODUCTION: Degenerative spondylolisthesis (DS) mainly occurs at L4-L5. The phenotype and critical values of facet joint (FJ) angulation and tropism (FJs angulation asymmetry) in relation to DS remain controversial. The study addressed the role of FJ angulation and tropism in relation to L4-L5 DS in the Asia Pacific region. METHODS: An international cross-sectional study was performed in 33 institutions of single level DS. Imaging assessment consisted of identifying the DS level and left/right L4-L5 FJ angulations. Patients were stratified to those without (Group A) or with L4-L5 DS (Group B). ROC and multivariate analyses were performed, assessing the FJ angulation profile and tropism in relation to DS. RESULTS: The study included 349 patients (63% females; mean age: 61.8 years). Group B had greater sagittal FJ angulation than Group A (p<0.001). 58 degrees or greater significantly increased the risk of DS (unilateral FJ: OR:2.5; 95% CI:1.2-5.5; bilateral FJ: OR:5.9; 95% CI:2.7-13.2; p<0.001). FJ tropism was found to be relevant between 16-24 degrees angulation difference (OR:5.6; 95% CI:1.2-26.1). CONCLUSIONS: To the authors’ knowledge, this is one of the largest studies to address the role of FJ angulation and tropism in relation to L4-L5 DS. Greater FJ angulation was associated with DS, with a critical value of ≥58 degrees increasing DS risk for unilateral and bilateral facet involvement. Specific FJT ranges were related to DS. This study further broadens the understanding of the phenotype of facet joint orientation in relation to DS.

Session: Free Papers Lumbar Spine 2: abstract no. 39935