title: Evaluation of subsidence, chondrocyte survival and graft incorporation following autologous osteochondral transplantation.
abstract: OBJECTIVE
  The aim of this study was to evaluate subsidence tendency, surface congruency, chondrocyte survival and plug incorporation after osteochondral transplantation in an animal model. The potential benefit of precise seating of the transplanted osteochondral plug on the recipient subchondral host bone ('bottoming') on these parameters was assessed in particular.
  
  
  METHODS
  In 18 goats, two osteochondral autografts were harvested from the trochlea of the ipsilateral knee joint and inserted press-fit in a standardized articular cartilage defect in the medial femoral condyle. In half of the goats, the transplanted plugs were matched exactly to the depth of the recipient hole (bottomed plugs; n = 9), whereas in the other half of the goats, a gap of 2 mm was left between the plugs and the recipient bottom (unbottomed plugs; n = 9). After 6 weeks, all transplants were evaluated on gross morphology, subsidence, histology, and chondrocyte vitality.
  
  
  RESULTS
  The macroscopic morphology scored significantly higher for surface congruency in bottomed plugs as compared to unbottomed reconstructions (P = 0.04). However, no differences in histological subsidence scoring between bottomed and unbottomed plugs were found. The transplanted articular cartilage of both bottomed and unbottomed plugs was vital. Only at the edges some matrix destaining, chondrocyte death and cluster formation was observed. At the subchondral bone level, active remodeling occurred, whereas integration at the cartilaginous surface of the osteochondral plugs failed to occur. Subchondral cysts were found in both groups.
  
  
  CONCLUSIONS
  In this animal model, subsidence tendency was significantly lower after 'bottomed' versus 'unbottomed' osteochondral transplants on gross appearance, whereas for histological scoring no significant differences were encountered. Since the clinical outcome may be negatively influenced by subsidence, the use of 'bottomed' grafts is recommended for osteochondral transplantation in patients.
authors: Orthopedic Research Laboratory, Department of Orthopedics, Radboud University Nijmegen Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
authors: Niels B
authors: NB
authors: Kock
authors: Gerjon
authors: G
authors: Hannink
authors: Albert
authors: A
authors: van Kampen
authors: Nico
authors: N
authors: Verdonschot
authors: Job L C
authors: JL
authors: van Susante
authors: Pieter
authors: P
authors: Buma
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000601:surgery*; D002470:Cell Survival; D019902:Chondrocytes / Q000637:transplantation*; D005260:Female; D006041:Goats; D006085:Graft Survival; D023421:Models, Animal; D011897:Random Allocation; D018709:Statistics, Nonparametric; D014182:Transplantation, Autologous; D014945:Wound Healing / Q000502:physiology