Reconstruction of rabbit Achilles tendon with three bioabsorbable materials: histological and biomechanical studies

This study investigated whether three biodegradable materials, poly-N-acetyl-D-glucosamine (chitin), poly-epsilon-caprolactone (p-CL), polylactic acid (PLA), and chitin/p-CL composite could be used as scaffold implants in the reconstruction of extra-articular ligaments or tendons. Braided artificial tendons made from these materials were soaked in phosphate-buffered saline or implanted in the subcutaneous tissue of 31 Japanese white rabbits and then subjected to load at failure testing. There was no significant loss of load at failure when chitin tendons were soaked in saline for 26 weeks, but a rapid decrease occurred in vivo. The other two types of tendons showed significant loss of strength after 26 weeks both in vitro and in vivo. Another 111 rabbits were used to assess Achilles tendon reconstruction with the braided tendon implants. The tendon regeneration process was assessed macroscopically, histologically, immunohistochemically, and mechanically (maximum load at failure). Chitin showed more rapid degradation than the other materials on histological examination. There was good formation of fibrous tissue composed of type I and type III collagen around the chitin, PLA, and chitin/p-CL fibers in comparison with p-CL fibers, but chitin tendons showed more rapid loss of strength after implantation. Both PLA and the chitin/p-CL composite tendons had good initial strength and showed increased ingrowth of fibrous tissue, suggesting that these materials are promising as artificial tendons.