Contact Pressure Comparison of Proud Osteochondral Autograft Plugs Versus Proud Synthetic Plugs

Abstract

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.

Synthetic PVA Osteochondral Implants for the Knee Joint: Mechanical Characteristics During Simulated Gait

“…While these values are low compared with native cartilage (6.3 ± 3.59 MPa), when confined in a defect, the instantaneous modulus of 20% PVA hydrogels is similar to the instantaneous modulus of native cartilage. 50 Finally, all implants were placed 0.2 mm proud, which improves the load-bearing capabilities of the implants 19,25 and avoids potential damage to opposing tissue in versions that have been kept as much as 1 mm proud. 53…”

“…While these values are low compared with native cartilage (6.3 6 3.59 MPa), when confined in a defect, the instantaneous modulus of 20% PVA hydrogels is similar to the instantaneous modulus of native cartilage. 50 Finally, all implants were placed 0.2 mm proud, which improves the loadbearing capabilities of the implants 19,25 and avoids potential damage to opposing tissue in versions that have been kept as much as 1 mm proud. 53 Of all implants tested, 20% PVA 1 pTi resulted in no significant difference in the sum of forces in the defect ROI when compared with the intact condition; a significant decrease in the sum of forces in the M-C ROI versus defect at 14% of the gait cycle; and a significant increase in the sum of forces in the C-C ROI versus defect at 45% of the gait cycle.…”

Ideal Donor Site for Osteochondral Autografting of the Distal Femur Using Radius of Curvature: A 3-Dimensional High-Resolution Scanner Comparison

“…It has been reported that there is a 21% to 57% increase in contact stress, with grafts that were only 1 mm proud. 33,34 Countersinking grafts may be more forgiving in terms of effecting contact pressures, but grafts sunk as little as 2 mm can lead to necrosis and fibrocartilage overgrowth. 34,35…”

“…Appropriate graft selection is believed to improve patient outcomes following OAT procedure and most agree that achieving anatomic restoration of the articular surface is of significant importance. 33,38,39 Attaining restoration requires consideration of many factors to include donor site morbidity, available surface area, and articular cartilage thickness. Donor site morbidity can be minimized by avoiding harvest in highly stressed areas.…”

Algorithm for Treatment of Focal Cartilage Defects of the Knee: Classic and New Procedures

“…If it is not possible to seat the graft perfectly flush, it is better for the graft to be slightly recessed than proud, as studies have shown that the graft being 1 mm proud equates to a 21% increase in peak contact forces. 125 Conversely, the plug being 2 mm recessed may result in cartilage necrosis or fibrocartilage overgrowth. 126 If the defect is large enough, mosaicplasty can be performed using similar concepts for each plug harvest and transfer.…”