Biomechanical evaluation of a new bone cement for use in vertebroplasty

Study Design. Comparative ex vivo biomechanical study. Objectives, To determine the strength and stiffness of osteoporotic vertebr al bodies subjected to compression fractures and subsequently stabilized vi a bipedicular injection of one of two bone cements: one is a commercially a vailable polymethylmethacrylate (Simplex P) and one is a proprietary glass- ceramic-reinforced BisGMA/BisEMA/ TEGDWIA matrix composite that is being de veloped for use in vertebroplasty (Orthocomp), Summary of Background Data. Osteoporotic compression fractures present diag nostic and therapeutic challenges for the clinician. Vertebroplasty, a new technique for treating such fractures, stabilizes vertebral bodies by injec tion of cement. Little is known, however, about the biomechanics of this tr eatment. Methods. Five vertebral bodies (L1-L5) from each of four fresh spines were harvested from female cadavers (age, 80 +/- 5 years), screened for bone den sity using DEXA (t = -3.4 to -6.4), disarticulated, and compressed in a mat erials testing machine to determine initial strength and stiffness. The fra ctures then were repaired using a transpedicular injection of either Orthoc omp or Simplex P and recrushed, Results. For both cement treatments, vertebral body strength after injectio n of cement was significantly greater than initial strength values. Vertebr al bodies augmented with Orthocomp recovered their initial stiffness; howev er, vertebral bodies augmented with Simplex P were significantly less stiff than they were in their initial condition. Conclusions. Augmentation with Orthocomp results in similar or greater mech anical properties compared with Simplex P, but these biomechanical results have yet to be substantiated in clinical studies.