Immediate versus delayed meniscal allograft transplantation in sheep.

The aim of the current study was to assess the effect of immediate and delayed transplantation on articular cartilage. Icelandic sheep had surgery on the medial menisci in both knees. The knees were divided into four groups; 16 control knees had sham surgery, 15 knees had meniscectomy, 14 knees had immediate allograft transplantation, and 14 knees had delayed transplantation 3 months after meniscectomy. The two horns of the fresh allograft were fixed with suture anchors through bone tunnels. The sheep had autopsies 6 months after surgery. An additional six knees were examined 3 months after meniscectomy to examine the cartilage before the delayed implantation. Four standardized samples were taken from the medial compartment of the knee for histologic evaluation according to a modification of Mankin's system, where degenerative changes to the articular cartilage were scored semiquantitatively for structure, proteoglycan content, cellularity, and cell cloning. Knees that had meniscectomy and delayed transplantation showed equally high scores in articular cartilage degeneration, and both scored higher than knees that had immediate transplantation, which again scored higher than the control knees. In short-term observations, immediate medial meniscal allograft transplantation reduced but did not prevent degeneration of the articular cartilage. Immediate transplantation was superior to delayed transplantation in preventing cartilage degeneration.