MR abnormalities of the intervertebral disks and adjacent bone marrow as predictors of segmental instability of the lumbar spine

Purpose: To assess whether MR abnormalities of the intervertebral disks and adjacent bone marrow can predict segmental instability of the lumbar spine as diagnosed on functional radiographs. Material and Methods: A consecutive review was made of 60 patients examined with MR imaging and with lateral flexion and extension views of the lumbar spine. Sagittal T1- and T2-weighted images were evaluated blindly with regard to abnormalities of the intervertebral disk and the adjacent bone marrow. Segmental instability was diagnosed when a.p. translation of 3 mm or more was present on the functional radiographs. Moreover, the presence of osteophytes was evaluated on lateral standard radiographs. Results. Of a total of 300 segments, 32 (10.7%) were unstable. Anular tears were the most relevant MR finding. Their sensitivity, specificity, and positive and negative predictive values for segmental instability were 18.8%, 97.0%, 42.9% and 90.9%. The corresponding values for traction osteophytes were 12.5%, 98.1%, 44.4% and 90.4%. Abnormalities of bone marrow were not significantly related to segmental instability (p=0.35). Conclusion. Functional radiographs should be considered in patients with anular tears or traction osteophytes. No correlation was found between segmental instability and abnormalities of bone marrow adjacent to the endplates.