title: Biomechanical and histological evaluations of the doubled semitendinosus tendon autograft after anterior cruciate ligament reconstruction in sheep.
abstract: BACKGROUND
  A sheep or goat anterior cruciate ligament (ACL) reconstruction model with the semitendinosus tendon autograft has not as of yet been established.
  
  
  OBJECTIVE
  The semitendinosus tendon graft may be necrotized after ACL reconstruction until 12 weeks. Structural properties of the femur-graft-tibia complex may not be restored to the normal ACL level even at 12 months after surgery.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Thirty-eight mature sheep were used. In each animal, the right knee underwent ACL reconstruction using the semitendinosus tendon autograft. Two of them were not tested because of pneumonia. Twenty of 36 sheep were used for biomechanical evaluations. Five randomly selected animals were sacrificed at 0, 12, 24, or 52 weeks after surgery. In each animal, both the knees were harvested, and the left knee was used to obtain the control data. The remaining 16 sheep were used for histological evaluation. Two or 3 randomly selected animals were sacrificed at 0, 2, 6, 12, 24, or 52 weeks after surgery.
  
  
  RESULTS
  The tendon graft was predominantly acellular at 2 weeks. Although cell infiltration increased at 6 weeks, the core portion remained necrotic even at 12 weeks. At 24 and 52 weeks, the necrotic lesion disappeared in the core portion. In each period, the anteroposterior translation of the reconstructed knee remained significantly greater than that of the control (P < .0001). At 52 weeks, the maximum load of the femur-graft-tibia complex was significantly lower than that of the femur-ACL-tibia complex (P < .0001), although there was no significant difference in the cell density, the tissue dimensions, the stiffness, and the elongation at failure between the 2 complexes.
  
  
  CONCLUSIONS
  The sheep ACL reconstruction model showed predominant intrinsic fibroblast necrosis in the tendon autograft until 12 weeks. Although the structural properties of the femur-graft-tibia complex gradually improved, they were not completely restored to the femur-ACL-tibia complex level even at 52 weeks.
  
  
  CONCLUSIONS
  Remodeling of the semitendinosus tendon autograft after ACL reconstruction is not different from that of the bone-tendon-bone graft. This study has suggested that vigorous activity should not be permitted for patients in the early periods after ACL reconstruction using semitendinosus tendon autografts, which are necrotized and weakened after surgery.
authors.affiliation: Department of Sports Medicine and Joint Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan. eijik@med.hokudai.ac.jp
authors.forename: Eiji
authors.initials: E
authors.lastname: Kondo
authors.forename: Kazunori
authors.initials: K
authors.lastname: Yasuda
authors.forename: Taro
authors.initials: T
authors.lastname: Katsura
authors.forename: Riku
authors.initials: R
authors.lastname: Hayashi
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kotani
authors.forename: Harukazu
authors.initials: H
authors.lastname: Tohyama
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D016118:Anterior Cruciate Ligament / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction; D001696:Biomechanical Phenomena; D005260:Female; D007719:Knee Joint / Q000601:surgery; D023421:Models, Animal; D009336:Necrosis; D012756:Sheep; D013710:Tendons / Q000473:pathology* / Q000503:physiopathology* / Q000637:transplantation; D013718:Tensile Strength; D014945:Wound Healing