Histologic evidence of absorption of sequestration-type herniated disc.

Study Design: The reactions to sequestrated disc fragments, which were removed surgically from 35 patients, were examined histologically.
Objectives: To elucidate whether or not there is histologic evidence of absorption of sequestrated discs.
Summary of Background Data: Spontaneous disappearance or diminution of lumbar herniated discs in the spinal canal has been recognized, and this could be a possible explanation for relief of symptoms without surgery. The mechanism of this phenomenon is unclear.
Methods: Sequestrated discs removed surgically from 35 patients were examined histologically.
Results: In 30 cases, neovascularization was observed at the periphery of the sequestrated discs. Many foamy cells (macrophages) were present in the vascularized areas. In addition, immunohistochemistry revealed that many spindle-shaped, fibroblast-like cells were positive for CD68, a marker of macrophages. No fibrous scar formation was observed in any region.
Conclusion: These findings suggest that organization is not a main course for this type of herniated disc and that a kind of "absorption" process occurs predominantly in the healing stage.