Osteochondral graft transplantation: relationship between graft insertion depth, insertion forces, cell death, and matrix degeneration (SS-41)

      Purpose: The objective of this study was determine the range of forces encountered during surgical insertion of osteochondral autografts and the effect on cellular viability and matrix degeneration. Methods: Osteochondral graft transplantation was performed in fresh frozen cadaveric knees. Forces required to extrude the cartilage from the harvester device, seat the cartilage flush with the surrounding cartilage and recess the cartilage 2 mm into the recipient site were measured using a uniaxial load cell. These forces were then applied to osteochondral grafts obtained form six fresh human femoral condyles harvested from total knee arthroplasty cases and one fresh normal knee. Applied loads varied from zero (sham) to 800 newtons. Chondrocyte viability and glycosaminoglycan release was determined at 48 and 120 hours post impact. Results: Graft insertion forces were relatively low (<400 newtons) during insertion or seating the graft compared to recession of the graft in the recipient site (max 800 newtons). A mean of 91% of the cells were viable in unimpacted grafts from the total knee specimens and nearly 100% for the fresh normal knee. Total knee specimens demonstrated 50% decreased in viability at 800N (P < .01). The fresh normal specimen demonstrated a significant decrease in viability approaching 20% at 400N and 800N (P < .01) at 120 hours post impact. Glycosaminoglycan release did not correlate significantly with insertion loads although there was a trend toward increased release with higher loads at 120 hours. Conclusions: Typical insertion loads for osteochondral grafting may not be immediately harmful to the cartilage implant but recession or placement of a graft into a relatively shorter recipient hole may reduce cellular viability in the graft.