Changes in vertebral bodies adjacent to acutely narrowed intervertebral discs: observations in baboons.

STUDY
DESIGN: The study used nonhuman primates to investigate changes in the vertebral bodies adjacent to acutely narrowed intervertebral discs.
OBJECTIVE: To describe changes in the vertebral bodies adjacent to acutely narrowed intervertebral discs in the lumbar spine. SUMMARY OF BACKGROUND DATA: Alterations in the intervertebral disc are known to affect the adjacent vertebral bodies. The consequences of sudden narrowing of the intervertebral disc on adjacent vertebral bodies have not been studied. We studied the effect of decompression of the normal primate IVD on the adjacent bone. The use of larger primates was appropriate for this study since the biomechanics of the spine on these animals mimics the human spine.
METHODS: Experiments were performed on 36 adult baboons. The intervertebral discs were decompressed with enzymes or surgically. On death at 4, 12, and 24 weeks, the spines were radiographed, sectioned, and photographed. The changes in the subchondral vertebral bone were documented. Segments were examined histologically.
RESULTS: At 24 weeks, 8 of 10 enzyme-injected discs (and at 14 weeks, 3 of 3 of the discectomies) contained semicircular yellowish-white areas in the bone adjacent to the narrowed discs. These showed bone marrow cell depletion and microfractures of trabecular bone. The lesions were most extensive following surgical nucleotomy. These changes were not seen following bone graft (0 of 4) or spacer replacement (0 of 4) of the intervertebral discs.
CONCLUSION: Alteration in vertebral bodies adjacent to suddenly narrowed intervertebral discs suggest trabecular bone response to physical stress. This is manifested by microfractures and bone marrow depletion.