The significance of increased fluid signal on magnetic resonance imaging in lumbar facets in relationship to degenerative spondylolisthesis.

STUDY DESIGN: Retrospective radiographic review of consecutive patients with universally applied standard.

OBJECTIVES: To define MRI findings at the facet joints that may suggest abnormal sagittal plane translation seen on standing lateral flexion-extension (SLFE) radiographs.

SUMMARY OF BACKGROUND DATA: MRI findings, including facet joint orientation, facet joint osteoarthritis, and the presence of synovial cysts, have all been linked with degenerative spondylolisthesis (DS). MRI can also detect facet joint effusion; however, there has not been a study specifically addressing the association of facet fluid signal to degenerative spondylolisthesis (DS).

METHODS: MRI and SLFE films of all patients seen at a single institution for an orthopedic spine consultation over a 2-year period were analyzed. The presence of facet effusions, synovial cysts, increased intensity within the interspinous ligament, degenerative changes at the facets, and anterior sagittal plane translation were all recorded. The data were analyzed to determine if there was a significant association between the presence of DS and the following: facet effusion, degenerative changes of the facets, synovial cysts, increased signal in the interspinous ligament, age, and gender.

RESULTS: There were 139 patients without DS at (NegDS) and 54 with DS (PosDS) on SLFE films at L4-L5 (n = 193). PosDS patients were more likely to be older (P < 0.0001), female (P = 0.0042), have synovial cysts (P < 0.0001), have higher osteoarthritis grade (P < 0.0001), and have larger facet effusion size (P < 0.0001). For both groups, facet joint effusions were also found to be significantly larger in patients with Grade 2 or less osteoarthritis, than in patients with Grade 3 osteoarthritis. Twenty-two percent of the listheses were not detectable on supine MRI.

CONCLUSION: Large (> 1.5 mm) facet effusions are highly predictive of degenerative spondylolisthesis at L4-L5 in the absence of measurable anterolisthesis on supine MRI. A clinically measurable facet effusion (> or = 1 mm) suggests the need for SLFE films to diagnose degenerative spondylolisthesis that can be missed with supine positioning on MRI.