Association of lumbar facet joint morphology with degenerative spondylolisthesis

Objective This study was designed to explore the role of lumbar facet joint morphology in the evolution of degenerative spondylolisthesis. Methods Forty-one subjects under the age of 60 years (mean 55 years) with degenerative spondylolisthesis at level L 4～5 and 32 subjects(mean 53 years)without degenerative spondylolisthesis were examined with computed tomographic scans to define the axial morphology of the facet joints.Assessments were made inclusive of the facet joint orientation, transverse articular dimension, depth of the articular surface, and shape of the articular surface at levels L 3～4 , L 4～5 , and L 5～S 1.In the second part of the study, we evaluated the morphology of the facet joint of 40 subjects under the age of 40 years and 40 subjects over 60 years with low back pain. Results The facet joint was oriented significantly more sagittally in the subjects with degenerative spondylolisthesis than those with no degenerative spondylolisthesis at the L 4～5 . The incidence of facet joint tropism and the depth ratios of the facet joint were also significantly different between these two groups of subjects. There was no statistical significant difference in the facet joint angles between subjects under the age of 40 years and those over the age of 60 years with low back pain. Conclusion These results suggested that lumbar facet joint morphology abnormalities were present in patients under the age of 60 years with degenerative spondylolisthesis. The facet joint sagittal alignment and/with tropism of the L 4～5 spine may be the critical risk factor of early degenerative spondylolisthesis.