AUTOLOGOUS TRANSPLANTATION OF RIB PERICHO NDRIAL GRAFTS FOR THE TREATMENT OF CARTILAGE LESIONS IN THE KNEE OF SHEEP - MORPHOLOGICAL COMPARISON FOLLOWING INTERNAL-FIXATION BY 2 DIFFERENT METHODS

The purpose of this study was to examine the fate of autologous perich ondrial -rafts after transplantation into cartilage lesions in weight- bearing joints, with reference to different fixation methods and diffe rent regimens of postoperative functional treatment. Full-thickness os teochondral lesions were drilled in the articular surface of knee join ts in 36 sheep. The defects were filled with autologous rib perichondr ial grafts, which were secured by either collagen sponges (group A; n = 12 animals) or fibrin glue (group B; n = 12 animals). Defects not fi lled with perichondrial grafts served as controls (group C; n = 12 ani mals). Following 1 week of immobilization of the treated leg, the plas ter was removed and the animals were allowed to move freely. Animals w ere sacrificed after 4, 8, 12 and 16 weeks. The -rafts were removed an d investigated histologically. In contrast to weight-bearing areas and control defects, hyaline-like cartilage formation could be noted in n on-weight-bearing areas after 4 weeks. This newly formed cartilage rev ealed strong metachromasie following staining with acidic toluidine-bl ue and reacted positively with PAS, indicating de novo synthesis of pr oteoglyvans and glycoproteins. Enzyme-histochemistry for alkaline and acid phosphatase activity showed positive reactivity only at the base of the transplants. Quantitatively, hyalin-like cartilage was achieved in 40/48 transplants from the non-weight-bearing area (20/24 transpla nts fixated with collagen sponge (group A); and 20/24 fixated with fib rin glue (group B). In control defects only fibrous scar tissue was de tectable. In transplants from the weight-bearing area only 7/48 (24 of group A and B each) a differentiation into hyalin-like cartilage was visible. Histological comparison revealed a subchondral transition zon e similar to enchondral ossification, following fixation with fibrin g lue, whereas in cases with collagen sponge fixation a broad zone of fi brous tissue was visible. Besides this, foreign-body giant cell format ion was detectable after the use of collagen sponges. From these resul ts fibrin glue is recommended for fixation of perichondrial grafts for the repair of full-thickness hyalin cartilage defects. This glueing t echnique allows secure graft fixation for necessary postoperative mobi lization.