title: Time dependence of changes of two cartilage layers in anterior cruciate ligament insertion after resection on chondrocyte apoptosis and decrease in glycosaminoglycan.
abstract: BACKGROUND
  The purpose of this study is to clarify the differences in time-dependent histological changes (chondrocyte apoptosis and glycosaminoglycan (GAG) layer thickness decrease) between uncalcified fibrocartilage (UF) and calcified fibrocartilage (CF) layers at the anterior cruciate ligament (ACL) insertion after ACL resection of rabbits.
  
  
  METHODS
  Forty male Japanese white rabbits underwent ACL substance resection in the right knee (resection group) and same operation without resection in the left knee (sham group). Animals were sacrificed 1, 2, 4 and 6 weeks after surgery.
  
  
  RESULTS
  In the UF layer, the apoptosis rate in the resection group was significantly higher than that in the sham group at 1 and 2 weeks. The GAG layer thicknesses of the UF layer in the resection group at 1, 2, 4 and 6 weeks were lower than those in the sham group. In the CF layer, the apoptosis rate in the resection group was significantly higher than that in the sham group at 2 and 4 weeks. The GAG layer thickness of the CF layer in the resection group was lower than that in the sham group only at 6 weeks.
  
  
  CONCLUSIONS
  The increase in chondrocyte apoptosis rate preceded the decrease in GAG layer thickness in both layers. In the UF layer, the increase in chondrocyte apoptosis rate and the decrease in GAG layer thickness preceded those in the CF layer. Using a surviving ligament and minimizing a debridement of ACL remnant during ACL reconstruction may be important to maintain cartilage layers of ACL insertion. An injured ACL should be repaired before degenerative changes of the insertion occur.
authors.affiliation: Department of Orthopaedic Surgery, Institute of Clinical Medicine, Graduate School of Comprehensive Human Science, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8575, Japan. sakane-m@md.tsukuba.ac.jp.
authors.forename: Masataka
authors.initials: M
authors.lastname: Sakane
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Mutsuzaki
authors.forename: Shinya
authors.initials: S
authors.lastname: Hattori
authors.forename: Hiromi
authors.initials: H
authors.lastname: Nakajima
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Ochiai