title: Weightbearing ovine osteochondral defects heal with inadequate subchondral bone plate restoration: implications regarding osteochondral autograft harvesting.
abstract: OBJECTIVE
  It is unknown what causes donor site morbidity following the osteochondral autograft transfer procedure or how donor sites heal. Contact pressure and edge loading at donor sites may play a role in the healing process. It was hypothesized that an artificially created osteochondral defect in a weightbearing area of an ovine femoral condyle will cause osseous bridging of the defect from the upper edges, resulting in incomplete and irregular repair of the subchondral bone plate.
  
  
  METHODS
  To simulate edge loading, large osteochondral defects were created in the most unfavourable weightbearing area of 24 ovine femoral condyles. After killing at 3 and 6 months, osteochondral defects were histologically and histomorphometrically evaluated with specific attention to subchondral bone healing and subchondral bone plate restoration.
  
  
  RESULTS
  Osteochondral defect healing showed progressive osseous defect bridging by sclerotic circumferential bone apposition. Unfilled area decreased significantly from 3 to 6 months (P = 0.004), whereas bone content increased (n.s.). Complete but irregular subchondral bone plate restoration occurred in ten animals. In fourteen animals, an incomplete subchondral bone plate was found. Further common findings included cavitary lesion formation, degenerative cartilage changes and cartilage and subchondral bone collapse.
  
  
  CONCLUSIONS
  Osteochondral defect healing starts with subchondral bone plate restoration. However, after 6 months, incomplete or irregular subchondral bone plate restoration and subsequent failure of osteochondral defect closure is common. Graft harvesting in the osteochondral autograft transfer procedure must be viewed critically, as similar changes are also present in humans.
  
  
  METHODS
  Prognostic study, Level III.
authors.affiliation: Julius Wolff Institute and Center for Musculoskeletal Surgery, Charité Universitätsmedizin Berlin, Augustenburger Platz 1, Forum 4, Postbox 24, 13353, Berlin, Germany. t.nosewicz@gmail.com
authors.forename: Tomasz L
authors.initials: TL
authors.lastname: Nosewicz
authors.forename: Mikel L
authors.initials: ML
authors.lastname: Reilingh
authors.forename: C Niek
authors.initials: CN
authors.lastname: van Dijk
authors.forename: Georg N
authors.initials: GN
authors.lastname: Duda
authors.forename: Hanna
authors.initials: H
authors.lastname: Schell
mesh_terms: D000818:Animals; D001861:Bone Regeneration; D016025:Bone Transplantation; D002358:Cartilage, Articular / Q000473:pathology / Q000502:physiology / Q000601:surgery*; D005260:Female; D005269:Femur / Q000473:pathology / Q000502:physiology / Q000601:surgery*; D051457:Hyaline Cartilage / Q000473:pathology / Q000502:physiology / Q000637:transplantation; D012756:Sheep; D013264:Stifle / Q000473:pathology / Q000502:physiology / Q000601:surgery*; D020858:Tissue and Organ Harvesting; D060053:Transplant Donor Site / Q000473:pathology / Q000502:physiology*; D014182:Transplantation, Autologous; D016474:Weight-Bearing; D014945:Wound Healing