title: Histologic changes after meniscal repair using radiofrequency energy in rabbits.
abstract: OBJECTIVE
  Our purpose was to investigate histologic changes in the rabbit meniscus after meniscal repair via radiofrequency energy (RFE).
  
  
  METHODS
  Twenty Japanese white rabbits underwent bilateral knee arthrotomies, and a longitudinal tear was made in the avascular area of both medial menisci. On the right knees, RFE treatment (60 degrees C and 40 W) was performed on the femoral surface of the meniscal tear in monopolar mode. On the left knees, the meniscus was left untreated as a control. The rabbits were killed at 0, 1, 2, 4, or 12 weeks after surgery, and all medial menisci were examined histologically. The expression of autocrine motility factor in meniscal fibrochondrocytes was examined by immunohistochemical analysis.
  
  
  RESULTS
  Histologic examination at baseline showed fusion of collagen fibers in the tear. Failure of fusion was found in 2 of 4 menisci at 2 weeks and 1 of 4 menisci at 4 and 12 weeks. One week after surgery, the specimens showed an acellular area as a result of fibrochondrocyte death. The acellular area expanded deeper until 4 weeks and was reduced at 12 weeks. On the femoral surface of the RFE-treated area, fibroblast proliferation was found at 2 weeks, and fibroblasts had invaded into the meniscus tissue from the meniscal surface at 12 weeks. Immunohistochemical analysis showed that the expression of autocrine motility factor in RFE-treated menisci was significantly higher than that in control menisci from 1 to 12 weeks.
  
  
  CONCLUSIONS
  RFE treatment at 60 degrees C and 40 W fused the collagen fiber in the meniscal tear in rabbits just after surgery. After RFE treatment, an acellular area developed as a result of fibrochondrocyte damage. RFE caused fibroblast proliferation at 2 weeks. The acellular area was reduced by cell repopulation at 12 weeks.
  
  
  CONCLUSIONS
  RFE may induce fibroblast proliferation for meniscal repair.
authors.affiliation: Department of Orthopaedic Surgery, Gunma University Faculty of Medicine, Maebashi, Japan. kazuhisa@zg7.so-net.ne.jp
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Hatayama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Higuchi
authors.forename: Masashi
authors.initials: M
authors.lastname: Kimura
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Takeda
authors.forename: Hideki
authors.initials: H
authors.lastname: Ono
authors.forename: Hideomi
authors.initials: H
authors.lastname: Watanabe
authors.forename: Kenji
authors.initials: K
authors.lastname: Takagishi
mesh_terms: D000818:Animals; D017115:Catheter Ablation; D005260:Female; D008592:Menisci, Tibial / Q000473:pathology* / Q000601:surgery*; D011817:Rabbits