Meniscal allografts.

Loss of the meniscus has been proved to be associated with increased joint pressures, mechanical changes, and ultimately hyaline cartilage degradation. Since the first arthritic changes following meniscectomy were appreciated, attempts have been made to alter and reverse the joint deterioration that occurs after removal of the knee fibrocartilage. Replacement of the fibrocartilage with either a prosthetic or biologic implant appears to be the only method of restoring normal joint anatomy. By inserting a meniscus substitute for the removed meniscus, the development of joint pathology should be avoided. This article focuses on the procedure of allogenic implants. Allogenic meniscal implants have been performed in humans for over 8 years. Recent clinical work has shown a rapid increase in the number of implants in the last 3 years with clinical review only now being presented. At present, the orthopedic surgeon has available cryopreserved, fresh-frozen, or frozen and irradiated tissue. Although much work has been performed in the animal with fresh-frozen tissue, the newly appreciated risk of disease transmission may require that all future implants be secondarily sterilized. Regardless of the type of implant, the early results of cell viability studies appear the same. Allogenic implants sustain new cellular ingrowth from the host and the DNA is replaced with host DNA. The ultimate success of this operation is not whether allogenic collagen can be transplanted into a host knee, but whether this tissue can be made to function and to preserve hyaline cartilage. Available data suggest that the technique being used to transplant the meniscus does not preserve normal meniscus function. These menisci may not function as they did in the donor. Additionally, few surgical techniques have been tested mechanically to compare meniscus function after transplantation. For these reasons, although transplant surgery for the meniscus remains an exciting and encouraging procedure to save the knee in a person who has had a total meniscectomy, the operation is currently being limited to those involved in study groups and investigational protocols. The long-term follow-up is at present limited or nonexistent. Objective parameters for evaluating posttransplant meniscus function are only now being collected and reviewed. Meniscal transplantation remains a cautiously optimistic treatment for the future.