Facet joint asymmetry and protrusion of the intervertebral disc.

In a study of 47 cases of lumbar disc protrusion, the hypothesis that asymmetry of the facet joints is correlated with the presence of a disc protrusion, was tested. Seventeen cases of protrusion of the L4-L5 disc and 30 cases of protrusion of the L5-S1 disc were measured on coronal computed tomography (CT) scans. The nonprotruded discs of each level were used as controls of the protruded discs of the same level. The transverse interfacet angle, the inclination and curvature of the facet joints, and the frequency of asymmetric facet joints showed no significant differences, whether there was a disc protrusion or not. The magnitude of the asymmetry was significantly greater only at the L4-L5 interspace in cases of disc protrusion. However, taking into consideration the error of measurement, the difference becomes highly questionable. These results do not indicate any relation between facet joint asymmetry and protrusion of the intervertebral disc.