Extraforaminal lumbar disc herniations: CT demonstration of Sharpey's fibers avulsion.

Forty-seven extraforaminal lumbar disc herniations (EFLDH) accounting for 7% of all lumbar disc herniations encountered during the same period of time were reviewed. L3-L4 or L4-L5 disc was involved in 89% of the cases giving rise to a L3 or L4 nerve root compression. An abnormal motion of lateral bending with rotation of the trunk was found retrospectively in 60% of the patients. In 53% of all EFLDH a bony avulsion of the vertebral end-plate facing the herniation was demonstrated at the site of attachment of Sharpey's fibers. This study suggests that this previously undescribed bony change witnesses a special injury of the spine responsible for most EFLDH.