Artificial biological ligament: its making, testing, and experimental study on animals

By applying a novel biochemical technique using porcine tendon as the raw material with its antigen minimized, we developed an artificial biological ligament (ABL). We examined and tested its structure, mechanical properties, and biocompatibility and explored the feasibility of reconstructing the anterior cruciate ligament (ACL) with ABL. By means of treating porcine tendon with epoxy crosslinking fixation, diversified antigen minimization process, mechanic enhancement modification, and surface activating process, we fabricated the ABL samples. We then analyzed its in vivo and in vitro performances, respectively, with animal (goat) implantation, histological examination, scanning electron microscope, cells culture, and mechanical tests before and after animal implants. The appearance of ABL was similar to that of normal human ligament. Histological examination showed that the ABL was composed of collagen fibers with no cells. Electron microscope examination revealed that the ABL was composed of hair-appearing and fiber-like objects running uniformly in a certain direction and closely parallel-arranged. Three weeks after xenogenic marrow matrix cells were cultured on the surface of the ABL, it was noted that cells adhered and the matrix secreted by the cells precipitated around the cells. There were no cells found inside the ABL. The average diameter of ABL was 5 mm and the mechanical test at a speed of 100 mm/min showed that its average tensile limit was 927.19 N; the tension-resistant strength was 47.22 N/mm. Those measurements were close to the corresponding parameters of the normal goat ACL. Twelve weeks after ABL replacement of the goat ACL, synovial membrane covering with the ingrowths of small blood vessels was seen on the surface of the implant. Fifty weeks after the replacement, the ABL material was partially replaced by regenerated host ligament-like tissue. Around the ABL material fibers in the bone tunnel close to the joint surface the direct connection mode, ligament-fibro cartilage-calcified cartilage-bone, was seen. As we used the unique biochemical technique and minimized the xenogenic protein immunogenicity of the porcine tendon, ABL showed acceptable biomechanical properties and superior biocompatibility. As a substitute for ligament in the reconstruction of the ACL, ABL has a promising prospect in clinical applications.