Histologic evaluation of human vertebral bodies after vertebral augmentation with polymethyl methacrylate

Histologic documentation of vertebral bodies retrieved from human patients.

The purpose of this study is to illustrate the histologic findings of two cases in which vertebroplasty and/or kyphoplasty had been performed.

There are a number of controversies to vertebral augmentation, including the use of inflatable bone tamps, use of nonstandardized polymethylmethacrylate (PMMA) preparations, the extent and significance of thermal necrosis, any foreign body reaction, and cement extravasation.

Four vertebral bodies from two cases ranging from 1 month to 2 years after surgery were analyzed histologically. Microscope slides of retrieved vertebral bodies were reviewed with special reference for evidence of thermal necrosis, foreign body reaction, migration of cement, cement voids and fractures, and for the influence of the bone tamp on adjacent bone.

The cancellous bone around the cement of the kyphoplasty specimen showed good density, suggesting that the tamping had displaced bone, essentially autografting the space around the cement. Bone immediately around the cement did not show extensive necrosis, but there were a few spicules of necrotic bone associated with creeping substitution, suggesting either thermal effect, the original fracture, or displacement of bone by the procedure. Foreign body giant cells and macrophages were identified in the fibrous membrane around the PMMA in all segments. These cells contained material consistent with cement particles and/or barium sulfate. Particles were also present within vascular spaces.

To our knowledge, these cases are among the first published reports of human histology after vertebral cement augmentation and have implications concerning the nature of the surgical procedures as well as the material used for injection.