Biomechanics of vertebral bone augmentation.

Percutaneous vertebral augmentation is a successful means of relieving pain and reducing disability after vertebral compression fracture; however, the exact mechanism by which vertebral augmentation eliminates pain remains unproven. Most likely, pain relief is because of stabilization of microfractures. The biomechanical effects of vertebral fracture and subsequent vertebral augmentation therapy, however, are topics for continued investigation. Altered biomechanical stresses after treatment may affect the risk of adjacent fracture in an osteoporotic patient; that risk may be different after vertebral augmentation with cavity creation (balloon assisted vertebroplasty or kyphoplasty) when compared with vertebral augmentation without cavity creation (vertebroplasty). Polymethyl methacrylate cement used in these procedures may have an important effect on the load transfer and disk mechanics, and therefore, the variables of cement volume, formulation, and distribution should also be evaluated. Finally, the question of whether prophylactic treatment of adjacent intact levels is indicated must be considered.