title: Repair of osteochondral defects in the knee by resorbable bioimplants in a rabbit model.
abstract: BACKGROUND
  The intrinsic healing capacity of articular cartilage remains poor, despite various attempts that have been undertaken to treat cartilage defects. This study describes the experimental use of a double-layer bioimplant consisting of a bone-substitute layer and a cartilage-substitute layer.
  
  
  METHODS
  In group A, 12 implants were placed into osteochondral defects of the load-bearing area of rabbit femoral condyles. In group B, 12 implantations were done in the same manner, with a separating membrane consisting of cement between both layers to investigate ingrowth of mesenchymal stem cells from the subchondral marrow space. Group C, with 12 similar defects but without treatment, served as control. Investigations by microscopy and immunohistochemistry were done after 12 weeks.
  
  
  RESULTS
  All bioimplants showed coverage of the defect with a regeneration tissue that contained cartilage-like regions. Implants with a cement layer showed less cartilage and more fibrous tissue. The bioimplant group showed more cartilage-like regeneration tissue than the control groups, which only showed incomplete fibrous filling of the defects. Results from the second group supported the hypothesis that the subchondral space must be opened for adequate regeneration. Additional examinations were done using an established semiquantitative score. The bioimplant group showed a significant improvement in results compared to the group with the separating layer and the control group.
  
  
  CONCLUSIONS
  Our findings indicate that cartilage repair by resorbable bioimplants seems to be a promising new approach, especially if mesenchymal stem cells are present and can differentiate under mechanical load.
authors.affiliation: Department of Orthopedics, Klinikum Grosshadern, Ludwigs-Maximilians-University Munich, Munich, Germany. peter.mueller@med.uni-muenchen.de
authors.forename: Peter E
authors.initials: PE
authors.lastname: Müller
authors.forename: Florian
authors.initials: F
authors.lastname: Schrimpf
authors.forename: Stephan
authors.initials: S
authors.lastname: Milz
authors.forename: Jörn
authors.initials: J
authors.lastname: Kircher
authors.forename: Hans Roland
authors.initials: HR
authors.lastname: Dürr
authors.forename: Bernd
authors.initials: B
authors.lastname: Wegener
authors.forename: Christoph
authors.initials: C
authors.lastname: Pellengahr
authors.forename: Volkmar
authors.initials: V
authors.lastname: Jansson
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D002358:Cartilage, Articular / Q000473:pathology / Q000502:physiology / Q000601:surgery*; D020007:Implants, Experimental; D007719:Knee Joint / Q000473:pathology / Q000502:physiology / Q000601:surgery*; D010007:Osteochondritis / Q000473:pathology / Q000601:surgery*; D011817:Rabbits; D014945:Wound Healing / Q000502:physiology