Biocompatibility and degradation of collagen bone anchors in a rabbit model

Bone anchors are used to fasten tendons and ligaments to bone during reconstructive surgery. Although metal anchors are often used, an anchor that could resorb and permit normal bone regeneration would be advantageous. The objective of the study was to evaluate the biocompatibility and degradation of bone anchors that consist of collagen-based bodies, ceramic washers, and polyester sutures. Eighteen rabbits underwent bilateral implantations in the distal femoral condyles. Nine animals received glutaraldehyde-crosslinked fibrillar collagen bone anchors (FC) and nine received glutaraldehyde-crosslinked fibrillar collagen bone anchors containing tricalcium phosphate (FC-TCP). Three animals per group were sacrificed at postimplantation weeks 1, 6, and 12. One femur from each rabbit was evaluated histologically, and the contralateral side underwent biomechanical pull-out testing. Histological evaluation of the implant site indicated that the FC and FC-TCP bone anchors were both biocompatible. The FC-TCP formulation degraded earlier than the FC formulation, and FC-TCP showed significant degradation at 6 weeks; the FC and FC-TCP formulations both showed similar amounts of degradation at 12 weeks. The degrading anchor bodies appeared to be osteoconductive as evidenced by new bone ingrowth into the degrading collagen matrices without a fibrous interface. These results suggest that collagen-based bone anchors have potential as bioresorbable orthopedic implants.