Histologic examination of meniscal repair in rabbits.

After a cylindrical defect was made in the anterior segment of the lateral meniscus in rabbits, the meniscus was examined postoperatively at 2, 8, and 13 weeks. Horizontal sections were prepared at a central level of the meniscus from each sample and stained with hematoxylin and eosin, Safranin O, and Masson trichrome. In addition, part of the tissue was immunologically stained with antibodies to chondroitin-4-sulfate, chondroitin-6-sulfate, keratan sulfate, and Type II collagen. Hematoxylin and eosin stained specimens were analyzed for repair tissue by microscopic study, and the cells observed in repair tissue were found to change from fibroblastlike cells to chondrocytelike cells with the progress of repair. Safranin O stained specimens showed a higher stainability with the progress of repair, confirming that abundant proteoglycan existed. In cases of complete healing, the repair tissue immunostained with antibodies to chondroitin-4-sulfate, chondroitin-6-sulfate, keratan sulfate, and Type II collagen showed a higher stainability than did the surrounding meniscus tissue. Thus, it is possible that the repair tissue might have been hyalinelike cartilage.