Chondrocyte-seeded hydroxyapatite for repair of large articular cartilage defects. A pilot study in the goat

The aim of this study was to evaluate the potential for restoration of a la rge cartilage defect in the goat knee with hydroxyapatite (HA) loaded with chondrocytes. Isolated chondrocytes were suspended in fibrin glue, seeded o n top of the HA, and then the composite graft was implanted in the defect. After transplantation, cell behaviour, newly synthesised matrix and the HA- glue interface were assessed histologically after 2, 4, 12, 26 and 52 weeks . Special attention was paid to the incorporation process of HA in the subc hondral bone and interactions between this biomaterial and the fibrin-glue- chondrocyte suspension. Chondrocytes in the glue proved to survive the transplantation procedure an d produced new metachromatically stained matrix two weeks after implantatio n. The glue-cell suspension had penetrated the superficial porous structure of the HA. Four weeks after surgery, islands of hyaline-like cartilage wer e observed at the HA-glue interface. A layer of fibrous tissue was formed s urrounding the HA graft, resulting in a relatively instable fixation of the HA in the defect. This instability of the graft in the defect, possibly to gether with early weight bearing, resulted in a gradual loss of the newly f ormed hyaline cartilage-like repair tissue. Progressive resorption of the H A occurred without any sign of active bone remodelling from the host site. One year after surgery part of the defect which extended down to the cancel lous bone had been predominantly restored with newly formed lamellar bone. Only small HA remnants were still present at the bottom of the original def ect. Resurfacing of the joint had occurred with fibrocartilaginous repair t issue. The absence of adequate fixation capacity of the Hd near the joint space re sulted in a relative instability of the graft with progressive resorption. Therefore, HA is not a suitable biomaterial to facilitate the repair of lar ge articular cartilage defects. (C) 1998 Elsevier Science Ltd. All rights r eserved.