Title: Bionate biocompatibility: In vivo study in rabbits

Abstract

We are investigating the adequacy of Bionate® 80A (Bionate® II PCU 80A, a thermoplastic polycarbonate-urethane) as the material for a new nucleus disc replacement design. Bionate® human explants (neurostimulation, vascular, artificial heart, cardiac assist and diagnostic devices) show minor wear and slight local tissue reaction, but we do not know the response at the spinal cord, nerve roots, lymph nodes, or distant organs. Objectives: Comparative in vivo study to evaluate the tissue reaction against Bionate® 80A when implanted at the spinal epidural space. Methods: Twenty-four 20-week-old New Zealand white rabbits were submitted for the same surgical procedure. In the implant group (n 12) we implanted Bionate® 80A powder particle sample on the spinal epidural space. The other 12 rabbits where the control group. We studied tissues, organs, and tissue damage markers on blood biochemistry, urine tests, and necropsy. Results: The animals’ clinical parameters and weight showed no statistically significant differences. At 3 months, the basophils increased slightly in the implant group, platelets decreased in all, and at 6 months, implanted animals showed slight eosinophilia, but none of these changes was statistically significant. External, organ, and spinal tissue examination showed neither toxic reaction, inflammatory changes, nor noticeable differences between groups or survival periods. Under microscopic examination, the Bionate® 80A particles induced a chronic granulomatous response always outside the dura mater, with giant multinucleated cells holding phagocytized particles and no particle migration to lymph nodes or organs. Conclusion: Bionate® particles, when implanted in the rabbit lumbar epidural space, do not generate a significant reaction, being it limited to giant multinucleated cells in the surrounding soft tissues. In addition, the particles did not cross the dura mater or migrate to lymph nodes or organs. This means, it could be used in the design of a nucleus disc replacement.