HEALING OF THE ANTERIOR ATTACHMENT OF THE RABBIT MENISCUS TO BONE

In a rabbit model the healing process of the anterior attachment of th e medical meniscus was observed during the first 12 weeks after sharp transection and refixation in a tibial bone channel, Evaluations of th e healing tissue were histologic analysis, application of immunohistoc hemical methods to show collagen types and nerve regeneration, and mec hanical load to failure tests, Secondary changes to knee joint cartila ge, as signs of eventual dysfunction of the refixed meniscus, were eva luated by analysis of proteoglycan fragment concentration in joint flu id and histologic analysis of knee joint articular cartilage and synov ium. The healing tissue between the refixed attachment and bone mature d from highly cellular, nonspecific granulation tissue at 1 week, to b one, fibrocartilaginous, and fibrous tissues, which at some sites de,d oped an insertion specific tissue arrangement within a la-week period, However, the irregular interface between the fibrocartilaginous tissu e and the underlying bone, which is typical for a normal insertion, wa s not reestablished, Labeling for collagen Types I and II in the newly formed insertion did not return to normal. In addition a fen. collage n fibers connected the refixed attachment tissue to bone, New bone for mation turned the initially cancellous bone tunnel walls into more sol id cortical bone, However, new bone formation did not fill the distal part of the channel, The refixed meniscal attachment underwent necrosi s and was revitalized by cell ingrowth from the periphery, Nerve fiber s were found in the newly formed insertion by 12 weeks. The failure lo ad at tensile testing never reached more than 20% that of a normal att achment, Degeneration of articular cartilage and increased proteoglyca n fragment in the joint fluid were common after this procedure, These data suggest that, despite the focal appearance of insertion specific tissues and healing of collagen fibers to bone, the tissue architectur e of a normal meniscal insertion and a normal meniscal joint protectiv e function were not reestablished.