Facet joint dilatation as a radiological indicator of vertebral segmental microinstability.

BACKGROUND: Chronic low back pain (LBP) is a major healthcare burden that reduces quality of life and productivity. Vertebral segmental microinstability is considered a contributing factor in LBP, while radiological signs reflecting biomechanical dysfunction, including disc degeneration, Modic changes, muscle fatty infiltration, and facet joint (FJ) dilatation, remain insufficiently defined as clinical markers. METHODS: This was a retrospective cohort study involving 168 adults with chronic LBP. Patients underwent clinical examination including passive lumbar extension (PLE), supine-sit, iliopsoas and quadratus muscle tests, along with lumbar spine magnetic resonance imaging. Imaging findings assessment included rating of FJ dilatation (grades 0-2), Modic changes (grades 0-2), disc degeneration (grades 1-5), and muscle fatty infiltration (grades 0-3). Pain intensity was measured using a 0-10 Visual Analog Scale. RESULTS: Among 168 patients, 70.5% (n = 120) demonstrated some degree of FJ dilatation, while 16.7% (n = 28) had high-grade dilatation. Dilatation was significantly associated with Modic type 1 changes, grade 4/5 disc degeneration, muscle fatty infiltration grade 2/3, positive PLE test, and FJ asymmetry. Three factors that did not significantly impact FJ dilatation included disc protrusion, supine-sit test, and muscle dysfunction test. CONCLUSION: For patients with chronic LBP, FJ dilatation is significantly associated with vertebral degeneration and clinical indicators of lumbar microinstability.