An ex vivo biomechanical evaluation of a hydroxyapatite cement for use with vertebroplasty

Study Design. Comparative ex vivo biomechanical study. Objective. To determine the strength and stiffness of osteoporotic vertebra l bodies subjected to compression fractures and stabilized via bipedicular injections of the following: 1) Simplex P (Stryker-Howmedica-Osteonics, Rut herford, NJ), 2) Simplex P formulated consistent with the practice of verte broplasty (F2), or 3) BoneSource (Stryker-Howmedica-Osteonics). Summary of Background Data. Little is known about the mechanical stabilizat ion afforded by new materials proposed for use with vertebroplasty. Methods. Vertebral bodies (T8-T10 and L2-L4) from each of 10 fresh spines w ere harvested from female cal davers (81 +/- 12 years), screened for bone d ensity (t Score, -3.8 +/- 1.1; bone mineral density, 0.75 +/- 15 g/cm(2)), disarticulated, and compressed to determine initial strength and stiffness. The fractured vertebral bodies were stabilized via bipedicular injections of 4 mL (thoracic) or 6 mL (lumbar) and then recrushed. Results. Vertebral bodies repaired with Simplex P resulted in significantly greater strength (P < 0.05) relative to their prefracture states, those re paired with BoneSource resulted in the restoration of initial strength for bath the thoracic and lumbar level, and those repaired with F2 resulted in significantly greater strength (P < 0.05) in the thoracic region and restor ation of strength in the lumbar region. All cement treatments resulted in s ignificantly less stiffness compared with initial values. Conclusions. All three materials tested restored or increased vertebral bod y strength,but none restored stiffness. Both new materials show promise for use in percutaneous vertebroplasty, but,they need clinical evaluation.