Proud osteochondral autograft versus synthetic plugs--contact pressures with cyclical loading in a bovine knee model

To determine whether proud synthetic and proud osteochondral plugs conform to native surrounding cartilage after cyclical loading and if there are differences in height and contact pressure after loading.

Sixteen bovine knees were used. Each received one osteochondral plug and one of two types of synthetic plugs (Smith & Nephew TruFit® BGS plug or Kensey Nash OsseoFit® plug). Plugs were placed in the center of each condyle's highest pressure area of articulation identified prior to defect creation (control). Static loads of 800N were applied and contact pressures measured with Tekscan sensors.

Both types of synthetic grafts and the osteochondral grafts all subsided with cyclical loading (p<0.001). The OsseoFit® plug displayed a greater reduction in height than the TruFit® plug compared to osteochondral grafts. The OsseoFit® plugs had significantly lower height than osteochondral grafts after both periods of cyclical loading (p<0.001), while height of the TruFit® plugs was not significantly different than the heights of osteochondral grafts after either first (p=0.387) or second (p=0.261) periods of cyclical loading. Contact pressures for the OsseoFit® plugs were significantly lower than contact pressures for osteochondral grafts after both periods of cyclical loading (p<0.001 for both). There was no difference between the pressures of TruFit® and osteochondral plugs after the first (p=0.381) or second (p=0.292) periods of cyclical loading.

Precision and accuracy are demanded to achieve flush osteochondral plug placement and OsseoFit synthetic plugs may subside more with less pressure than TruFit plugs if placed proud.