Background: Autologous osteochondral transfer is an option for the
treatment of articular defects. However, there are concerns about graft
integration and the nature of the tissue forming the cartilage-cartilage
bridge. Chondrocyte viability at graft and recipient edges is thought to be an
important determinant of the quality of repair. The purpose of the present
study was to evaluate early cell viability at the edges of osteochondral
grafts from ex vivo human femoral condyles.
Methods: Fresh human tissue was obtained from eleven knees at the
time of total knee arthroplasty for the treatment of osteoarthritis.
Osteochondral cylinders were harvested with use of a 4.5-mm-diameter
mosaicplasty osteotome from regions of the anterolateral aspect of the femoral
condyle that were macroscopically nondegenerate and histologically
nonfibrillated. Plugs were assessed for marginal cell viability by means of
confocal laser scanning microscopy.
Results: The diameter of the cartilaginous portion of the
osteochondral plugs was a mean (and standard error of the mean) of 4.84
± 0.12 mm (as determined on the basis of three plugs). This value was
approximately 300 µm greater than the measured internal diameter of the
osteotome. There was a substantial margin of superficial zone cell death (mean
thickness, 382 ± 68.2 µm), with >99% cell viability seen more
centrally (as determined on the basis of five plugs). Demiplugs were created
by splitting the mosaicplasty explants with a fresh number-11 scalpel blade.
The margin of superficial zone cell death at the curved edge was significantly
greater than that at the site of the scalpel cut (390.3 ± 18.8 µm
compared with 34.8 ± 3.2 µm; p = 0.0286). Similar findings were
observed when the cartilage alone was breached and the bone was left intact,
with the margin of superficial zone cell death being significantly greater
than that obtained in association with the straight scalpel incision (268
± 38.9 µm compared with 41.3 ± 13.4 µm; p = 0.0286). The
margin of superficial zone cell death showed no increase during the
time-period between fifteen minutes and two hours after plug harvest. A
mathematical approximation of the mosaicplasty region suggested that early
cell death of this magnitude affects about one third of the superficial graft
Conclusions: The results of the present study suggest that
mosaicplasty, while capable of transposing viable hyaline cartilage, is
associated with an extensive margin of cell death that is likely to compromise
lateral integration and articular reconstruction.
Clinical Relevance: The data suggest that there is a need to improve
the plug-harvest technique, which may improve graft-recipient healing and