Histologic changes in the disc after cervical spine trauma: evidence of disc absorption.

We examined the histologic changes in the disc in two cases of traumatic cervical disc herniation and compared it with previous histologic studies done in degenerative disc herniations. Differences in the absorption of herniated cartilage endplate and annulus fibrosus are also discussed. The herniated disc material was surrounded by fibrovascular tissue. Vessels in this fibrovascular tissue were seen to continue into the annulus fibrosus but not into the endplate. Scattered cartilage fragments and macrophages in the fibrovascular tissue were localized around the margin of the disc. The herniation produced a visible defect in the injured intervertebral disc. On serial sections, the amount of herniated annulus fibrosus appeared to be smaller than the defect produced in the annulus fibrosus of the injured disc. However, the herniated endplate seemed to be the same size as the defect produced in the endplate of the injured disc. Fibrovascular tissue formation, vessel infiltration into annulus fibrosus, and the presence of peripheral macrophages suggest marginal absorption. The cartilage fragments are probably remnants of disc tissue produced during the process of absorption. These findings are similar to that seen in degenerated herniated discs and suggest an absorptive process. Absorption of the annulus is more significant than absorption of the endplate.