Impaction affects cell viability in osteochondral tissues during transplantation

Symptomatic full-thickness defects of articular cartilage are increasingly treated with osteochondral allografts. The present study focused on the viability of cells in cartilage that had been impact loaded by the instruments used in preparation of the cartilage for transplantation. Osteochondral plugs were removed and reimplanted using a plastic tamp device fitted with a load cell. Plugs were examined at time 0 or after 48 hours or 7 days of tissue culture. During insertion, the force was 25 +/- 6 N and increased with time to a peak of 307 +/- 84 N. On average, 18 taps were necessary for the insertion of each plug, and the applied total impulse ranged from 5.7 to 17.8 N. Peak force and total impulse were highly correlated (R2 = 0.76, P < .001). Typically, a loading cycle lasted <10 milliseconds with peak loading rates up to 133 +/- 25 kN/s for each individual plug. The loading rate was dependent on the peak force, ie, the higher the applied load, the higher the rate. Cell death was 60% in the upper zone for all groups at all time points and lower (20%) for the middle and deep zones. Cell death appeared to be higher in all zones of the impacted group. Investigating the whole plug at time 0, cell viability was significantly lower for the impacted plugs compared to control (dead: P < .02, living: P = .05). After 48 hours, as well as after 7 days, mean cell viability remained affected. These data suggest that the range of loading used in the manipulation of cartilage tissue in transplantation must be carefully considered if cell preservation is to be maintained.