MRI T2-mapping of lumbar facet joints is effective for quantitative evaluation of lumbar instability in patients with degenerative lumbar disorders

Purposes To analyze T2 relaxation times of the facet joint by MRI T2-mapping in patients with degenerative lumbar disorders (DLD), and to determine the correlation with lumbar instability in radiographs. Methods We conducted a T2-mapping of the lumbar facet joint using a 1.5 T MRI system. We classified patients with degenerative lumbar disorders scheduled to undergo decompression surgery into groups with stability and instability using radiographs, and compared the T2 relaxation times of the lumbar facet. Lumbar instability was defined as the presence of anterior translation ratio > 5% or disk range of motion (ROM) > 5° in the sagittal plane of SLFE radiographs. Results Inclusion criteria were met by 22 patients (45 levels, mean age 64.3 years). Facet effusions had high sensitivity (90%) but had low specificity (28%) for diagnosis of lumbar instability. Mean T2 relaxation times of right and left facet joints are significantly longer (98.4 ms) in the instability group than they are (87.6 ms) in the stability group ( p < 0.001). Anterior translation ratio was positively correlated with mean T2 relaxation times of facet joint ( R 2 = 0.493, p < 0.05). From a ROC analysis, the cutoff value of T2 relaxation times for lumbar instability was 98.65 ms (sensitivity 60.0%, specificity 95.7%, AUC 0.763). Conclusions The T2 relaxation times were positively correlated with lumbar instability. This new quantitative evaluation of lumbar facet joint using MRI T2-mapping might be useful to determine lumbar instability.