Histologic changes after vertebroplasty.

BACKGROUND: Vertebroplasty with use of polymethylmethacrylate cement is gaining popularity in the treatment of some specific painful lesions of the spine. It remains unclear, however, what possible side effects this type of cement might have upon the vertebral body. We performed a histologic and radiographic analysis of the end plate and disc to determine whether there was a difference between vertebroplasty with polymethylmethacrylate cement and vertebroplasty with calcium phosphate cement in the surrounding tissue of the goat spine. Furthermore, we assessed whether a defect in the end plate, simulating end-plate fracture and allowing for direct contact of cement with disc tissue, had any effect on end-plate or disc degeneration.
METHODS: Twenty-four mature goats were divided between two follow-up periods (six weeks and six months). All animals underwent a bilateral transpedicular vertebroplasty at two lumbar levels, where one of the following treatments was applied: vertebroplasty with calcium phosphate cement with or without an end-plate defect, and vertebroplasty with polymethylmethacrylate cement with or without an end-plate defect. The effect of the various treatments on the integrity of the intervertebral disc, end plate, and surrounding tissue was examined with semiquantitative histologic analysis and radiography.
RESULTS: No sign of disc or end-plate degeneration was seen in any of the analyzed sections. The mean disc height did not decrease from the postoperative period to the time that the animals were killed in any group, thereby supporting the histologic findings. A mild inflammatory reaction was found in four vertebral bodies in the polymethylmethacrylate groups only.
CONCLUSIONS: Calcium phosphate cement and polymethylmethacrylate cement both seem to be adequate bone-void fillers in terms of biological behavior in the vertebral body.