Biologic anchorage of cruciate ligament prosthesis. Bone ingrowth and fixation of the Gore-Tex ligament in sheep.

The biologic fixation and strength of fixation of the polytetrafluoroethylene (PTFE) Gore-Tex ligament prosthesis was investigated in sheep knees. The device was inserted to replace the anterior cruciate ligament according to the recommended technique. Histological bone tunnel evaluation together with mechanical tensile studies were done at 6, 12, and 18 months. Already at 6 months the pull-out load of the prosthesis exceeded that of the normal ligament, and this finding persisted up to 18 months postoperatively. At 6 months there was marked fibrous tissue ingrowth into the prosthesis, and at 12 months trabecular bone had replaced the fibrous tissue between the interstices of the filaments; at 18 months bone even penetrated into the individual porous fibers of the prosthesis. The intra-articular part of the prosthesis was surrounded and partly invaded by undifferentiated connective tissue, with no recognizable macrophages or other inflammatory cells. In this experiment, the biocompatibility and porosity of the Gore-Tex prosthesis seemed optimal to permit ingrowth from surrounding fibrous and osseous tissues and firm anchorage into the bone tunnels.