Chondrocyte damage following osteochondral grafting using metal and plastic punches: comparative study in an animal model.

PURPOSE Osteochondral impaction grafting to manage isolated chondral defects in femoral condyles usually uses a metal punch to impact the grafts into predrilled cavities. Damage to the chondrocytes during impaction is a concern, however, and new methods are being sought to minimise the damage. We studied if impaction with a plastic punch instead of a metal punch reduces the extent of chondrocyte damage in an animal model. METHODS 32 osteochondral plugs were prepared from knees of 10 freshly slaughtered sheep knees; the contralateral condyles were then prepared to receive the osteochondral grafts. 20 plugs were impacted into predrilled holes: 10 using a metal punch and 10 using a plastic punch. The 12 remaining plugs were used as controls. The plugs were recovered, incubated for 24 hours in calf serum, and stained with 3-[4,5-dimethylthiazol]-2,5-diphenyltetrazolium to measure the content of viable cells. Digital photographs of the stained cartilage were then analysed on a 0-to-255 grey-scale. RESULTS We found no significant difference in the extent of chondrocyte damage caused by impaction using metal and plastic punches. The content of viable cells in plugs impacted by metal and plastic punches, however, was significantly lower than that in the control plugs, as reflected by higher means of light intensity of 52.9 (p<0.001) and 32.4 (p=0.005), respectively. CONCLUSION Impaction grafting clearly damages chondrocytes of the osteochondral plug. The use of a plastic punch does not reduce the extent of chondrocyte damage during the impaction grafting procedure.