Potential Healing of Meniscal Injuries in the Avascular Zone after Radiofrequency Stimulation (SS-34)

Abstract

Meniscal repair in the white-white zone has a high incidence of failure due to poor vascularity. Radiofrequency application has been shown to increase the angiogenic capabilities of fibroblasts in chronic tendinopathies. The purpose of this study was to evaluate the effect of radiofrequency (RF) stimulation, in conjunction with suture repair, on the healing of tears in the white-white zone of the meniscus. 54 New Zealand white rabbits underwent surgically induced meniscal injuries within the avascular (white-white) region. Rabbits were then divided into three treatment groups: no repair (N=6), suture repair only (N=15) and suture repair in conjunction with RF treatment (N=33). Radiofrequency was applied using a 0.8 mm radiofrequency wand at level 4 for 500 milliseconds. Rabbits were then sacrificed at 9, 28 and 84 days for gross, histological and biochemical examination by two blinded observers. Biochemical analyses included evaluation of cell proliferation (3H-thymidine) as well as mitogenic (IGF-1, bFGF) and angiogenic (VEGF, αV) factors. Of specimens repaired with radiofrequency combined with suture, 19 (58%) showed increased gross morphologic and histological healing compared to controls. Two meniscal explants treated with RF had complete histological healing. No significant healing was seen in specimens that had either no repair or repair with suture alone. Biochemically, at nine days, the rate of 3H-thymidine for meniscal tears treated with suture repair + RF was 590±80 cpm/mg dry tissue. This value was approximately 40% greater than the menisci treated with suture repair only, which had a value of 380±30 cpm/mg (p < 0.05). Normal, unrepaired meniscal tissue had a 3H-thymidine incorporation rate of 250±35 cpm/mg. Semiquantitative RT-PCR analysis showed that at nine days post-repair, the RF-treated menisci had significantly increased mR.N.A expression of IGF-1, bFGF, VEGF and αV relative to untreated repairs. By day 28 and 84, the levels appeared equivalent between all treatment groups (p > 0.05). This study demonstrated that in our animal model, radiofrequency application in adjunct to suture repair of white-white meniscal tears led to a significantly increased healing response both in vitro and in vivo. Although the mechanism by which RF stimulation improves the healing response is not completely understood, our biochemical analyses suggest that it may enhance cellular proliferation as well as the mitogenic and angiogenic capability of the meniscal fibroblast.