Contact pressure comparison of proud osteochondral autograft plugs versus proud synthetic plugs

Osteochondral autograft transfer is an accepted treatment for chondral and osteochondral defects of the knee. Synthetic plugs may eventually be used for primary treatment of defects. Currently they are largely used for osteochondral donor site backfill. Placement of osteochondral or synthetic plugs proud leads to articulating surface incongruity, increases in contact pressure, and potential for both plug and opposing surface degenerative change. We conducted a biomechanical study of human cadaver knees to determine whether differences exist in the contact pressure of osteochondral autograft plugs placed proud versus synthetic plugs placed proud. Ten human cadaveric knees were used (20 condyles). Contact pressure was measured with Tekscan sensor technology (South Boston, Massachusetts) with both static and cyclical loads (of 250 and 500 cycles) created by an MTS Bionix system (Eden Prairie, Minnesota) under the following conditions: native articular cartilage, surgically created defect (7-mm diameter), 1-mm proud osteochondral autograft, and 1-mm proud synthetic graft. Proud osteochondral autograft plugs resulted in a 21.4% increase in peak contact pressure over surrounding native articular cartilage versus a 4.9% increase with proud synthetic plugs. Synthetic plugs compressed their structure and subsided versus subchondral bone collapse with compressive load in osteochondral autograft plugs. Proud osteochondral autograft plugs have significantly higher peak contact pressures than proud synthetic plugs when placed for treatment of chondral and osteochondral defects in the knee.