The Bio-integration Profile of Fiber-Reinforced Plates Following Tibial Implantation in Sheep.

Bio-integrative, mineral fiber-reinforced bone fixation implants recently introduced in orthopedic surgery have expanded available treatment options for fractures and bone deformities. This new technology aims to address the disadvantages of permanent metallic implants while overcoming inherent concerns of adverse inflammatory reactions when using polymer-based orthopedic implants. The purpose of this double-arm preclinical study was to evaluate the safety, biocompatibility and bio-integration of fiber-reinforced plates, following implantation on the tibias of eight sheep. Left tibias underwent periosteal elevation, allowing for implant attachment directly onto the cortical surface; right tibia plates were implanted over intact periosteum. Microcomputed tomography and histopathology were performed at 13, 26, 52, 78, 104, and 134 weeks post-implantation. All animals were evaluated clinically at each time point, with no evidence of local adverse reactions. Histopathology demonstrated anti-inflammatory M2-like macrophages and multinucleated giant cells (MNGCs) corresponding to implant bioabsorption, similar for both groups at each time point, and indicating expected implant biocompatibility. Inflammatory cells (i.e., eosinophils, lymphophyctes, plasma cells, and M1-like macrophages) were absent throughout the study. The bioabsorption process had started at 13W, with the highest rate at 52W to 78W. At 104W, only residual polymer material was left (~5% of implant area). Low amounts of mineral fibers were evident at 78W and were absent (fully remodeled) by 104W. At 134W, implants at both sites were fully bioabsorbed. In conclusion, these new fiber-reinforced implants demonstrated bone remodeling and complete bio-integration, with no adverse tissue response. This article is protected by copyright. All rights reserved.