Histologic changes in articular cartilage after medial meniscus replacement in rabbits

Meniscal allografts show capsular ingrowth, but it remains to be established whether meniscal transplantation can prevent long-term degeneration of articular cartilage. This study examined whether immediate or delayed transplantation of the medial meniscus can protect the knee from degenerative changes.

Experimental study.

Thirty-five rabbits were divided into 5 groups. Three rabbits developed infective arthritis and were excluded from the study. Group A (6 animals) and group C (6 animals) had meniscectomy only; group B (7 animals) and group D (6 animals) underwent meniscal transplantation immediately after meniscectomy; group E (7 animals) had delayed transplantation 6 weeks after meniscectomy. Six nonoperated knees served as controls. Histologic changes of the articular cartilage were examined 6 weeks (groups A, B) and 1 year (groups C, D, E, controls) after surgery.

All operated groups showed more histologic changes than the control group (P < .00001 for both the medial tibial plateau and medial femoral condyle in all groups). At 6 weeks follow-up, no differences were found between the postmeniscectomy group and the transplanted group. At 1 year, immediately transplanted knees showed less degenerative changes than meniscectomized knees (P < .0001 for medial tibial plateau and P < .005 for medial femoral condyle). Delayed transplantation resulted in more degenerative changes than both meniscectomy only and immediate transplantation (for both comparisons, P < .00001 for both medial tibial plateau and medial femoral condyle).

Immediate meniscal transplantation in rabbits has a protecting effect on articular cartilage for the long-term whereas delayed transplantation leads to even more degenerative changes than meniscectomy only.

If these results are applicable to humans, they would support immediate, not delayed, transplantation after removal of a meniscus.