Correlation Between Calcification of Facet Joint Capsule and Dynamic Instability in Lumbar Degenerative...

To evaluate the association between facet joint capsule calcification (FCC) on computed tomography and dynamic instability on weight-bearing flexion-extension lateral X-ray in patients with degenerative spondylolisthesis at L4-5.

Clinical and radiologic data from 388 patients with degenerative spondylolisthesis who underwent lumbar magnetic resonance imaging, computed tomography, and dynamic X-ray within a 1-month interval from January 2012 to December 2021 were reviewed in this study. Radiologic factors associated with dynamic instability were evaluated: FCC, facet degeneration grade, facet joint fluid, facet tropism, disc degeneration grade, traction spur, and vacuum phenomenon. We evaluated the association between FCC and dynamic instability and determined the best cutoff value of cross-sectional area (CSA) of FCC for predicting dynamic instability.

The FCC, facet joint degeneration, disc degeneration grade, and traction spur were significantly correlated with dynamic instability. The optimal cutoff point of the average CSA of FCC was measured at 14.46 mm2 with 82.3% and 96.0% sensitivity and specificity, respectively, with an area under the curve of 0.950. In the distribution in CSA of FCC according to grade of facet joint degeneration, the best cutoff value of CSA of FCC related to dynamic instability, 14.46 mm², is almost the same as the mean value of CSA of FCC for grade 2 of facet joint degeneration.

FCC is significantly correlated with dynamic instability in degenerative spondylolisthesis at L4-5. FCC is a radiologic finding that can be helpful in detecting dynamic instability together with dynamic X-ray.