OSTEOCHONDRAL REPAIR USING PERICHONDRIAL CELLS - A 1-YEAR STUDY IN RABBITS

Articular cartilage repair remains a clinical and scientific challenge with increasing interest focused on the transplantation of chondrogen ic cells, This study evaluated the repair response during a 1-year per iod after implantation of allogenic perichondrium cell polylactic acid composite grafts into 3.7 x 5 mm osteochondral defects drilled into t he medial femoral condyles of 82 adult New Zealand White rabbits. The repair tissue was evaluated grossly, histologically, histomorphometric ally, biochemically, and biomechanically at 6 weeks, 12 weeks, 6 month s, and 1 year after implantation, After gross evaluation, cartilaginou s material appeared to fill the defeet in 70 experimental knees, for a n overall repair frequency of 85%. The histomorphometric results and t he histologic appearances were variable, None of the specimens were co mpletely normal at 1 year. Only specimens with subchondral bone reform ation displayed a definable cartilage appearing surface with chondrocy tes surrounded by dense matrix, Subchondral bone reformation was incon sistent, reaching 50% at 1 year. Biochemically, the repair tissue matu red during a 1-year period into a hyaline Type II collagen dominant ti ssue, whereas glycosaminoglycan content remained low at all time perio ds, The measured compressive properties of the repair tissue at 1 year were not significantly different from those of the contralateral knee that was not surgically treated. The treatment of osteochondral defec ts in the rabbit knee with allogenic perichondrium cell polylactic aci d composite grafts yielded a high percentage of grossly successful rep airs that showed inconsistent subchondral bone reformation, These resu lts suggest that healthy subchondral bone is important to articular ca rtilage repair, They also highlight that a cartilaginous appearing tis sue at gross inspection may not represent structurally normal articula r cartilage, Continued multidisciplinary studies on the arthroplastic potential of rib perichondrial cells are needed before human studies, which rarely can extend beyond gross assessment of repair tissue appea rance can be undertaken.