Effect of vertebral cement augmentation with polymethylmethacrylate on intervertebral disc and bone tissue

Vertebral cement augmentation is reported to be a safe and effective technique for providing stabilization and pain relief. However, adjacent intervertebral discs may be at risk of accelerated degeneration as a result of aggravated nutritional constraints. Therefore, we investigated the effects of injecting polymethylmethacrylate (PMMA) into three adjacent lumbar vertebrae on intervertebral disc and vertebral bone tissue in 12 skeletally mature sheep. After 6 and 12 months of augmentation, the sheep were euthanized and their spines were processes for histological evaluation. Semiquantitative histomorphological analysis of discs and endplates was conducted using published criteria. Histomorphological changes in the augmented bone were assessed qualitatively. Approximately 80% of the length of the endplates was in contact with PMMA. However, there was no significant difference between the histopathological score of the discs adjacent to augmented vertebrae and the score of the control discs. Bone tissue reaction to PMMA was characterized by a thin fibrous tissue layer and occasional foreign-body reactions. New bone formation was present in all augmented vertebrae. Concerns about aggravation of disc degeneration as a result of vertebral cement augmentation seem to be unsubstantiated. Furthermore, adverse effects of PMMA cement on bone biology do not seem to be a relevant issue.