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Abstract & Commentary
Synopsis: Rasping of torn meniscal surfaces in the avascular zone expressed cytokines on these surfaces. It is suggested that this may be the key to explaining the mechanism of vascular induction and meniscal healing by meniscal rasping.
Source: Ochi M, et al. Expression of cytokines after meniscal rasping to promote meniscal healing. Arthroscopy. 2001;17(7): 724-731.
Many advocates of meniscal repair have attempted to extend the indications for repair into the so-called avascular (white-white) zone of the meniscus using a variety of adjunctive measures. Ochi and colleagues propose a "new" method to promote meniscal healing in this zone of the meniscus. The method involves rasping of not only the perimeniscal synovium, but also the meniscal surfaces, including the injured site.
In an experimental, randomized trial of 26 rabbits, longitudinal "tears" were surgically created in the avascular zone of the medial menisci of both knees. On the right knee of each rabbit, meniscal rasping was done on the femoral surface from the perimeniscal synovium to the inner portion of the tear, the left knee was not rasped. Four rabbits were killed for immunohistochemical analysis at the following intervals: 1, 7, 14, 28, 56, and 112 days. Immunostaining for IL-1 alpha, TGF-beta 1, PDGF, and PNCA was accomplished. A positive ratio of each of the cytokines was present at varying times in the experimental groups. IL-1 alpha peaked at day 1, TGF-beta 1 and PCNA both peaked at 7 days, and PDGF peaked at 14 days after surgery. Ochi et al conclude that these cytokines, induced by rasping not only the perimeniscal synovium, but the meniscus to include the tear itself, may stimulate the recruitment and the proliferation of cells and synthesis of collagen, leading to healing of a meniscal tear in the avascular zone.
Comment by Mark D. Miller, MD
In a well-done experiment using an animal model, Ochi et al report encouraging research on the possibility of extending meniscal healing to the avascular zone of the meniscus. Unfortunately, it is a bit premature to conclude that the mere presence of these factors is enough to result in successful repair in the avascular zone. A variety of enhancement techniques such as fibrin clot, trephination, fibrin glue, and rasping have been used to extend the envelope for meniscal repair. Ochi et al’s technique for meniscal rasping is, in fact, not new. In a study of meniscal repair in the goat model, we used a similar technique of meniscal rasping in the avascular zone with encouraging results.1 Although we were not aware that the inducement of cytokines was responsible for this response, we did describe this technique for meniscal rasping. The discovery of cytokines, induced by rasping, is encouraging and may explain our improved results in this experimental group. Further experimental and clinical application of these findings is clearly needed.
1. Ritchie JR, et al. Meniscal repair in the goat model. The use of healing adjuncts on central tears and the role of magnetic resonance arthrography in repair evaluation. Am J Sports Med. 1998;26:278-284.