Intravertebral body reconstruction with an injectable in situ-setting carbonated apatite: Biomechanical evaluation of a minimally invasive technique

The ability to mechanically reinforce an osteoporotic vertebral body could impede spinal compression fracture and the associated pain and complication s. Previous studies have shown that reinforcement of fractured vertebrae wi th conventional acrylic cement can relieve symptoms and avoid further colla pse. In this study, we explored the use of a carbonated apatite cement comb ined with a minimally invasive injection technique to improve the compressi ve mechanical properties of cadaveric vertebral bodies, After establishing the biomechanical characteristics of cement formulations intended to have a ppropriate viscosities, we evaluated the infiltration of the cements into t horacic vertebral bodies using a combined suction-injection technique. The energy-absorption capabilities of the reinforced vertebral bodies were then measured during axial compressive tests and compared with those of nonrein forced vertebrae. The ultimate compressive strength of the cement formulati ons averaged from 11.6 to 17.7 MPa. depending on curing conditions. The suc tion-injection technique allowed from one-half to two-thirds of each verteb ral body to be infiltrated with cement. Energy absorption was significantly higher (p < 0.05) between 25 and 70% collapse of the vertebral body in the specimens that received the apatite injection as compared with the control s. These results suggest that osteoporotic vertebral-body augmentation with the injection of apatite cement could prevent further collapse after initi al failure has occurred. The osteoconductive nature of the cement and its a bility to be remodeled by bone, together with its compressive strength, whi ch is higher than that of cancellous bone, could provide better clinical re sults than those of current treatments with acrylic cement.