Cartilage properties after allogeneic transplantation of cryopreserved osteochondral plugs and cartilage-bone paste-grafts
Gole, Madhura Dilip
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Articular cartilage has a limited capacity to heal due to the avascular nature of the tissue. A lesion that traverses the full thickness of cartilage and penetrates the subchondral bone plate will have access to subchondral blood flow. Blood-borne inflammatory mediators trigger a repair response that culminates in fibrocartilage repair tissue that may fill the lesion site. Unfortunately, fibrocartilage cannot withstand the physiologic load-bearing required of articular cartilage and begins to degenerate within a year. The aim of this research was to determine if transplantation of allogenic tissues could result in repair tissue that was more similar to native articular cartilage than to fibrocartilage. The first study, performed in 5 sheep, compared the transplantation of cryopreserved osteochondral allografts to fresh autografts (a clinically established technique) at one year after transplantation. The second study, performed in 40 rabbits, evaluated repair tissue properties 6 months after allogeneic cartilage and bone paste-graft implantation. In both studies, repair tissue was evaluated by the following techniques: macroscopic and histologic appearance, cartilage firmness, and chondrocyte viability. Viability was quantified through digital analysis of confocal microscopy images. In addition, sulfate-uptake analysis, an indicator of cartilage metabolism, was performed in the cryopreserved osteochondral allograft study. At one year, cryopreserved osteochondral allografts performed better when transplanted into load-bearing sites compared to those in non-load-bearing areas. Loadbearing grafts demonstrated macroscopic appearance, cartilage firmness, cell metabolism and viability similar to fresh osteochondral autografts and adjacent articular cartilage. Paste-graft tissue, evaluated at six months, was significantly inferior to intact articular cartilage, but superior to fibrocartilage repair tissue. Paste-graft properties were not affected by load-bearing site, the ratio of cartilage to bone within the paste-graft mixture, or by the use of fibrin sealant as an adhesive. While osteochondral allograft provided functional restoration of the articular surface, both repair techniques resulted in repair tissue that was inferior to native articular cartilage. However, both techniques demonstrated improvements in the quality of repair tissue compared to previous studies.