Clinical study on the 3D morphology and mechanical factors of lumbar facet joints in patients with degenerative lumbar spondylolisthesis

Aims: To construct a mechanical model using a spatial Cartesian coordinate system and vectors, and to explore the role of facet joint morphology and mechanical parameters in degenerative lumbar spondylolisthesis (DLS). Methods: A retrospective imaging study was conducted to collect the demographic data and imaging parameters of patients with and without DLS. The 3D structure and mechanical parameters of facet joint were constructed for comparative analysis. Receiver operating characteristic and regression analysis explore predictors for DLS. A total of 149 patients (67.8% female) were included in the study, with a median age of 63 years (IQR 58.5 to 68.0). Results: Compared with non-DLS patients, there were significant differences in the facet joint angle (FJA), facet degeneration of L4-5, the sagittal joint angle (SJA), and intervertebral angles of L3-5 in DLS. Regardless of correction, the L4-5 posterior shear force of DLS patients is smaller than non-DLS. Posterior shear force has a high area under the curve and is significantly different from FJA, medial shear force, and vertical stress. High SJA and low posterior shear force are independent predictors for the progression of lumbar spondylolisthesis. Conclusion: In addition to the FJA, the larger SJA and lower posterior shear forces are also a good index to predict the progress of DLS. The posterior shear force is a more valuable indicator for predicting DLS progression, and may be a direct factor in the anterior displacement. When the posterior shear force is less than 0.537, the possibility of lumbar spondylolisthesis greatly increases. At this time, even in cases where patients do not experience spondylolisthesis, muscle exercise or intraoperative fixation are recommended to maintain lumbar stability.