Biomechanical Evaluation of a New Bone Cement for Use in Vertebroplasty

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Abstract
Comparative ex vivo biomechanical study. To determine the strength and stiffness of osteoporotic vertebral bodies subjected to compression fractures and subsequently stabilized via bipedicular injection of one of two bone cements: one is a commercially available polymethylmethacrylate (Simplex P) and one is a proprietary glass-ceramic-reinforced BisGMA/BisEMA/TEGDMA matrix composite that is being developed for use in vertebroplasty (Orthocomp). Osteoporotic compression fractures present diagnostic and therapeutic challenges for the clinician. Vertebroplasty, a new technique for treating such fractures, stabilizes vertebral bodies by injection of cement. Little is known, however, about the biomechanics of this treatment. Five vertebral bodies (L1–L5) from each of four fresh spines were harvested from female cadavers (age, 80 ± 5 years), screened for bone density using DEXA (t = −3.4 to −6.4), disarticulated, and compressed in a materials testing machine to determine initial strength and stiffness. The fractures then were repaired using a transpedicular injection of either Orthocomp or Simplex P and recrushed. For both cement treatments, vertebral body strength after injection of cement was significantly greater than initial strength values. Vertebral bodies augmented with Orthocomp recovered their initial stiffness; however, vertebral bodies augmented with Simplex P were significantly less stiff than they were in their initial condition. Augmentation with Orthocomp results in similar or greater mechanical properties compared with Simplex P, but these biomechanical results have yet to be substantiated in clinical studies.