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

Purpose: 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. Methods: 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 800. N were applied and contact pressures measured with Tekscan sensors. Results: 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. Conclusions: 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.