[Visco-elasticity of transplanted menisci in rabbits. A correlative histological and hydrodynamical studies].

The purpose of this study is to investigate the visco-elasticity, histology and hydrodynamics of transplanted menisci following transplantation. Experiments to examine visco-elasticity are performed on 30 rabbits, to examine NMR on 20 rabbits and on 12 rabbits respectively for histological study. Under intravenous general anesthesia the medial meniscus was completely resected, and a cryopreserved allograft meniscus was implanted. The rabbits are sacrificed 1, 2, 3 and 5 months post-operatively, and the implanted menisci are removed for examination. One month after surgery, dynamic stiffness is markedly lower in the implanted menisci than in the controls. Thereafter, it gradually increased. Three months after surgery, there is no significant difference between the transplanted menisci and the controls. However the value of tan delta which serves as indicator of dynamic visco-elasticity is larger in the implanted menisci than in the control specimens throughout the experiment. The water content was higher in the transplanted menisci throughout. The 1H-NMR relaxation time (T2) was markedly prolonged 1 month post-operatively, but shortened rapidly after that. Nevertheless, it is still longer than in the control specimen after 5 months. In the histological study, no chondrocytes are observed in the transplanted menisci, and the matrix was poorly stained with Eosin 1 month after surgery. Thereafter, granulomatous tissues proliferated in the menisci, and by 5 months after surgery, the chondrocytes appear to be almost normal. However, matrix was weakly stained with Eosin. These results suggest that the interactions between high molecular weight matrix and water in transplanted menisci are different from those in normal menisci, and that therefore the viscosity of transplanted menisci is higher.