[Meniscus transplantation using a cryopreserved allograft--an experimental study in the rabbit]

In twenty rabbits with completion of bone growth, the medial meniscus was replaced with an allograft meniscus that had been preserved at -80 degrees C for 6 to 14 days. As a control, the medial meniscus was removed and reattached without cryopreservation in 14 rabbits. Replaced menisci were examined histologically and microangiographically. Allografted menisci were found to attach to the capsule at 4 weeks. However, the attachments of the anterior and posterior horns were not stable in the majority of rabbits, because the nylon thread for anchoring was broken in these cases. There was osteophyte formation on the medial tibial plateau and the medial femoral condyle. Histological examinations revealed proliferation of vascularized synovial tissue along the meniscal surface and invasion of para-meniscal connective tissue into the meniscal substance. Chondrocytes showed regeneration in the superficial layer at 12 weeks. This study has demonstrated that cryopreserved meniscal allograft was capable of regeneration. The osteophyte formation of the medial femoral condyle and the tibial plateau appears to be produced by the abnormally unstable transplanted meniscus resulting from the insufficient anchorage of anterior and/or posterior horns.