title: Sequential changes in implanted cartilage after autologous osteochondral transplantation: postoperative acoustic properties up to 1 year in an in vivo rabbit model.
abstract: OBJECTIVE
  For successful autologous osteochondral transplantation, it is important that the cartilage in an implanted plug provide histologic replacement of damaged cartilage with cartilage that is structurally and mechanically normal. The purpose of this study was to investigate whether the press-fit technique reconstructs the normal hyaline cartilage and provides acoustic stiffness equal to that of normal intact cartilage.
  
  
  METHODS
  In 36 rabbits an osteochondral plug, 6 mm in diameter, was removed from the right patellar groove and grafted into a recipient hole, 5 mm in diameter, in the left patellar groove. Specimens at 2, 4, 8, 12, 24, and 52 weeks postoperatively were assessed by macroscopic and histologic observation and by use of an ultrasonic system. The ultrasonic acoustic stiffness, acoustic surface irregularity, and acoustic thickness of the implanted cartilage were examined and compared with normal intact cartilage.
  
  
  RESULTS
  The gross appearance of the implanted cartilage was glossy, maintained good surface smoothness, and survived well throughout the observation period. The cartilage recovered histologic features of hyaline cartilage. The acoustic stiffness decreased up to 12 weeks and then increased at 24 and 52 weeks after surgery. The acoustic stiffness at 8 or 12 weeks was significantly lower (acoustically softer) than that of control cartilage (P < .001). The acoustic stiffness at 52 weeks was equal to that of the control. The difference in acoustic surface irregularity was not significant. The acoustic thickness at 8 weeks was higher (acoustically thicker) than that of the control (P < .01).
  
  
  CONCLUSIONS
  Although the reason acoustically soft cartilage in plugs becomes acoustically stiff and whether the histology of the implanted cartilage had recovered completely remain unclear, the acoustic stiffness recovered to normal control values by 52 weeks postoperatively.
  
  
  CONCLUSIONS
  Postoperative care for up to 12 weeks should be taken after autologous osteochondral transplantation.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kuroki
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Nakagawa
authors.forename: Koji
authors.initials: K
authors.lastname: Mori
authors.forename: Masahiko
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Okamoto
authors.forename: Ko
authors.initials: K
authors.lastname: Yasura
authors.forename: Kohei
authors.initials: K
authors.lastname: Nishitani
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakamura
mesh_terms: D000818:Animals; D016025:Bone Transplantation / Q000000981:diagnostic imaging / Q000473:pathology; D002358:Cartilage, Articular / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000637:transplantation; D051457:Hyaline Cartilage; D008297:Male; D011184:Postoperative Period; D011817:Rabbits; D013997:Time Factors; D014182:Transplantation, Autologous; D014463:Ultrasonography