The fate of osteochondral grafts after autologous osteochondral transplantation: a one-year follow-up study in a minipig model.
BACKGROUND
Because articular cartilage shows little intrinsic capacity of spontaneous regeneration, a variety of treatment options are currently at use to repair cartilage damage. One of these is the autologous osteochondral transplantation (AOT). The aim of the present work was to study the histological changes during the progress of 1 year after AOT in the knee joint.


METHODS
Twelve Minipigs underwent an AOT on the medial femoral condyles of both knees using cooled diamond studded trephines with a diameter of the grafts of 4.6 mm. Three animals were sacrificed at each 2, 8, 26 and 52 weeks after the operation. The condyles were analyzed histologically and immunohistologically for collagen types I and II.


RESULTS
A successful bony incorporation was observed in all specimens. The transplant demonstrated an increasingly stable integration of the chondral matrix into the cartilage of the surrounding femoral condyle. At 52 weeks after the operations 5 of 6 condyles showed a chondral integration at least at one side of the graft. Immunohistologically all specimens showed physiological staining characteristics up to 52 weeks after operation. The quality of the chondral part of the graft showed a wide range of variations, ranging from vital tissue resembling native cartilage after 52 weeks, to severe degenerative signs beginning 2 weeks after operation and ending at 52 weeks with deep fissures fragmenting the cartilage and the complete loss of vital cells.


CONCLUSIONS
The press-fit technique allows a stable bony incorporation. A chondral integration of the graft seems to occur, provided that a close contact between the interfaces can be achieved. Present results demonstrate a vital cartilagenous transplant for up to 52 weeks. However, some specimens showed in part severe degenerative signs. A possible explanation is an insufficient cooling of the trephines in relation to the small diameter of the grafts used in the minipig model. The collagen network seems not to be affected for up to 52 weeks.
Department of Trauma, Hand and Reconstructive Surgery, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
Klaus
K
Baumbach
Jan-Philipp
JP
Petersen
Peter
P
Ueblacker
Jens
J
Schröder
Christiane
C
Göpfert
Alexander
A
Stork
Johannes M
JM
Rueger
Michael
M
Amling
Norbert M
NM
Meenen
D000818:Animals; D016025:Bone Transplantation; D002356:Cartilage / Q000637:transplantation*; D002357:Cartilage Diseases / Q000473:pathology* / Q000601:surgery*; D004195:Disease Models, Animal; D005500:Follow-Up Studies; D007719:Knee Joint / Q000473:pathology* / Q000601:surgery*; D013552:Swine; D014182:Transplantation, Autologous