Is lumbar facet joint tropism developmental or secondary to remodeling changes? An international, large-scale multicenter study by the AOSAP collaboration consortium

Abstract

INTRODUCTION: Facet joint tropism is asymmetry in orientation of the bilateral facets. Some studies have shown that tropism may increase the risk of disc degeneration and herniations, as well as degenerative spondylolisthesis (DS). It remains controversial whether FJT is a pre-existing developmental phenomena or secondary to progressive joint remodeling. The following study addressed the occurrence of FJT of the lower lumbar spine (i.e. L3-S1) in a degenerative spondylolisthesis patient model. METHODS: This was an international, multi-center cross-sectional study of 267 patients with single level DS recruited from 33 spine institutes in Asia Pacific. FJT (≥8 degrees asymmetry) was assessed on MRI from L3-S1 and in relation to the level of DS. Patient demographic were noted and assessed in relation to FJT of each lumbar segment. RESULTS: 65% were females (mean age of 63 years; mean BMI: 26 kg/m2). FJT was present in 31.3% to 50.6% of DS levels. FJT involved 33.3% to 58.8% of the one or two non-DS levels adjacent to the DS level. Patient demographics were not found to be significantly related to FJT at any level (p>0.05). CONCLUSION: To the authors’ knowledge, this is one of the largest studies conducted, in particular in an Asian population, addressing the “origins concept” of FJT. Although levels with DS were noted to have FJT, adjacent levels with no DS also exhibited tropism and were not related to age and other patient demographics. This study suggested that FJT may have a pre-disposed orientation.