Tears of the anulus fibrosus: correlation between MR and pathologic findings in cadavers

Tears of the anulus fibrosus, which have been implicated in back pain, have not been studied systematically with MR imaging. We correlated MR images with cryomicrotome sections to study the lumbar anulus fibrosus in 20 cadavers. Three distinct types of tears of the anulus were identified: concentric tears, characterized by fluid-filled spaces between adjacent lamellae; radial tears, characterized by a rupture of all layers in the anulus between the nucleus and the surface of the disk; and transverse tears, characterized by a rupture of Sharpey's fibers in the periphery of the anulus, near the ring apophysis. In each type, fluid or mucoid material was present in the tear. MR demonstrated the transverse and radial tears. We conclude that MR imaging provides an accurate means for investigating tears of the anulus.