Incidence of unfused ossicles in the lumbar facet joints: CT, MR, and cryomicrotomy study.

The incidence of unfused ossicles in the lumbar spine, in radiographic studies, is 0.7-1.5%. With a sledge cryomicrotome, we sectioned 273 lumbar facet joints in 38 adult cadavers and correlated the anatomic appearance of the joints with CT and magnetic resonance (MR) images. Ossicles were present in 13% of the cadavers and 2.6% of the facet joints and were demonstrated effectively by MR. The incidence of ossicles, which can be confused with fractures, in the facet joints is higher than previously reported.