Biomechanical and Radiographic Comparison of Demineralized Bone Matrix,and a Coralline Hydroxyapatite in a Rabbit Spinal Fusion Model

The use of bone grafts is an essential component in spinal fusion. Autologous bone has been shown to result in long-term stable arthrodesis between spinal motion segments. However, autograft can be associated with significant morbidity and a limited supply. Alternatives, such as allogeneic demineralized bone matrix (DBM), are a potential source and supplement to autograft bone. The current study compares the ability of a DBM product (BioSet^® RT) and a coralline hydroxyapatite (Pro Osteon^® 500R), for inducing spinal fusion in a rabbit model. BioSet^® RT, alone or in combination with autograft, and Pro Osteon^® 500R were implanted in the posterior lateral inter-transverse process region of the rabbit spine. The spines were evaluated at 18 weeks for fusion of the L4—L5 transverse processes using a total of 33 skeletally mature male rabbits; 4 naïve animals were also included in the study. Samples were evaluated radiographically, histologically, by palpation, and through mechanical strength testing. Radiographical, histological, and palpation measurements demonstrated the ability of BioSet^® RT to induce new bone formation and bridging fusion comparable to autograft. This material performed well alone or in combination with autograft material. Despite significantly higher biomechanical testing results, minimal bone formation and fusion was recorded for the Pro Osteon^® 500R-treated group. This in vivo study demonstrates the ability of BioSet^®RT to induce new bone formation, and there was a clear relationship between bridging bone and mechanical strength.