The Role of L4-L5 Facet Joint and Disc-Related Anatomy in Lumbar Spondylolisthesis: An Imaging Study.

STUDY DESIGN: Retrospective cohort.

OBJECTIVE: To compare morphologic anatomic features of individual with L4-L5 degenerative pathology with and without listhesis to identify predictive factors of instability.

SUMMARY OF BACKGROUND DATA: Aging-related degenerative changes in the lumbar spine can lead to instability in the form of a listhesis. Previous studies have identified elements of lumbar facet joint morphology that may be risk factors for instability when compared to an asymptomatic population.

METHODS: Patients with single-level L4-L5 degenerative pathology, with or without spondylolisthesis, who underwent L4-5 surgery were evaluated. Facet joint anatomic features were measured on standing radiographs and supine MRI. Multivariate stepwise regression was used to identify anatomic factors associated with L4-5 spondylolisthesis. Outcomes included: (1) change in % listhesis from standing radiographs to supine MRI, (2) change in listhesis between flexion and extension radiographs, (3) change in translation from standing radiographs to MRI, and (4) change in L4-5 disc angle between standing radiographs and MRI. Univariate Pearson correlation was performed for the strongest predictors.

RESULTS: Among 231 L4-L5 surgical patients (100 with spondylolisthesis; mean age 64.3 ± 12.6; BMI 29.0 ± 5.9; 23.8% female), anterior disc height predicted % listhesis change from MRI to standing radiographs (β=-0.33, P=0.01). Middle disc height predicted change in disc angle (β=-1.17, P=0.01). Anterior disc height correlated with preoperative listhesis (r=-0.51, P<.001). Facet effusion width predicted flexion-extension disc angle change (β=0.32, P=0.05).

CONCLUSIONS: In L4-L5 degeneration, spondylolisthesis was associated with sagittal facet orientation, greater effusion, and reduced anterior disc height, which most strongly correlated with increased translation. These features help interpret differences between standing radiographs and MRI and may assist in identifying segments where instability should influence surgical planning.