Allograft meniscus transplantation in the dog.

We studied transplantation of a fresh meniscus in 25 knees in 15 adult dogs. On 2 tables and with 2 surgical teams the medial menisci were explanted, exchanged and implanted into the opposite dog's knee. The animals were killed 4-12 months postoperatively, and the transplants were studied histologically. Complete healing in the host's capsular tissues was found in 18 knees, incomplete healing in 3, and healing by massive fibrovascular scar tissue in 4 knees. In the 4- and 5-month specimens the transplants were found to be narrower, thinner, and of changed color and consistency, while in the 8- and 12-month specimens most of the allografts appeared grossly normal. Histologically, the allografts had normal general microarchitecture, but a marked decrease in the number of cells. In the 8- and 12-month specimens the cells had increased but the number of cells in general was still less than in the controls. Although some degenerative changes of the medial tibial articular cartilage were noted in most knees, there were less changes beneath the allografted meniscus.