INTRAOSSEOUS INCORPORATION OF COMPOSITE COLLAGEN PROSTHESES DESIGNED FOR LIGAMENT RECONSTRUCTION

Composite collagen prostheses are potentially useful for reconstructio n of the anterior cruciate ligament (ACL). We evaluated the intraosseo us response to composite collagen prostheses to determine if ''biologi cal fixation'' could be used to secure the prostheses within surgical bone tunnels. The rate of degradation of the prosthesis and the respon se of the tissue were evaluated, as a function of collagen crosslinkin g agent and time, in nonloaded bone tunnels in rabbits. Prostheses wer e fabricated by the alignment of 200 reconstituted type-I collagen fib ers (60 mu m in diameter) and the embedding of the fibers within a col lagen matrix. The prostheses degraded rapidly within the bone tunnels in comparison with soft-tissue implantation sites. Dehydrothermal-cyan amide crosslinked collagen fibers were completely degraded by 8 weeks. Only 10% of glutaraldehyde crosslinked collagen fibers remained intac t at 12 weeks. Fibrous tissue and inflammatory cells rapidly infiltrat ed the prostheses, and new bone surrounded the circumference of the pr ostheses, advancing toward the center at longer times. At the lateral cortex, where fibrous tissue emerged, the bone/soft-tissue interface w as delineated by a tidemark, similar to that observed in a normal liga ment insertion site. Preliminary pull-out testing of the soft tissue f rom the bone was discontinued because failure consistently occurred in the soft tissue; this suggests rapid incorporation of the prostheses within the bone tunnels. Composite collagen prostheses designed for AC L reconstruction degrade rapidly in bone and induce rapid ingrowth of fibrous tissue and bone. These results suggest that tissue ingrowth in the bone tunnels might provide biological fixation for collagen prost heses used for ACL reconstruction.