Aim: To evaluate the role of facet tropism as an etiological factor in lumbar intervertebral disc prolapse. Setting: Medical college teaching hospital from South India Design: Case series analysis Methods: The study included MRI scans of 120 patients which were studied by Heithoff's technique. The facet angles of each segment were measured by Cyron and Hutton's method. The association of asymmetry of lumbar facets and low back pain was studied. Results: In 80 patients with MRI showing disc prolapse, there was more asymmetry of lumbar facets compared to 40 patients with low back pain but MRI showing no disc prolapse. Although facet tropism was observed in subjects with MRI showing no disc prolapse, it was encountered far more frequently in patients with disc prolapse. It was seen that lateral disc prolapse occurred more frequently in patients with facet tropism and the prolapse tended to occur more frequently on the side where facet angle was lower. The results showed no significant association between facet tropism and lumbar disc prolapse. Conclusion: Facet tropism may be one of the causes of back pain because altered mechanism of the spinal motion segment. The association of facet tropism and lateral disc herniation needs to be investigated further before attributing a causal relationship.

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