The prevalence of lumbar facet joint edema in patients with low back pain

Objective The objective was to assess the prevalence of lumbar facet joint edema in patients with low back pain. Materials and methods Lumbar spine MR examinations (1.5 T) of 145 consecutive patients (87 women, 58 men; mean age 52.8, range 17-94 years) were retrospectively evaluated with regard to the presence of facet joint edema. The MR protocol included sagittal short-tau inversion recovery (STIR), T1- and T2-weighted as well as transverse T2-weighted images. In 9 patients follow-up MR examinations were performed and results were compared with pain. The agreement between the change in intensity of facet joint edema and the change in intensity of pain was assessed using kappa statistics and Kendall's tau coefficient. Results In 21 of the 145 patients (14%) edema was found at the facet joints: in 52.4% at L4/5, in 19.0% at L5/S1, in 14.3% at L4/5 and L5/S1, in 9.5% at L3/4 and L4/5, and in 4.8% at L3/4. The agreement between the change in pain score and intensity of edema within the follow-up group was "almost perfect" (kappa=0.81). Kendall's tau coefficient was 0.91, indicating high agreement. Conclusion Sagittal STIR images detect facet joint edema in 14% of patients with low back pain. This fact may be useful for planning treatment including facet joint injections.