Preserved and foreign cartilage interpositional materials for silastic finger joint implant arthroplasty

Cartilage grafts were implanted as interpositional materials (IPMs) around the stems of silicone finger joint prostheses to protect their surfaces from abrasion with the local bone tissue. The knee joints of New Zealand White rabbits were implanted with finger joint prostheses and grafted with preserved auto- and allografts as well as fresh xenografts. Data were obtained after one month and compared to controls that received only the silicone prostheses. The grafting procedures did not cause any variations in joint function or differences in the amount of lipids absorbed by the prosthesis. A thin fibrous capsule formed about the control implants, whereas the capsules of the grafted legs were greater in thickness and area. Gross examination of the implant surfaces, weight analyses, and light microscopic studies of the number of wear particles found in the surrounding tissue capsules all indicated a reduction in prosthetic wear with grafting. The cartilage grafts were surrounded by inflammatory cells and were losing their proteoglycans. As expected, the xenografts exhibited the most degradation. No differences were noted between the preserved grafts. These results indicate that at one month, cartilage has provided protection for early implant motion. The biodegradable graft was being replaced by fibrous connective tissue. Long-term protection needs to be studied in additional experiments.