Manual punch versus power harvesting of osteochondral grafts

Purpose: The purpose of the study was to analyze the effect on chondrocyte viability of 2 existing methods of harvesting osteochondral grafts used for articular cartilage resurfacing. Type of Study: Acute animal experiment. Methods: Power (P) trephine versus manual (M) punch harvesting was tested; 2.7-mm and 4.5-mm dowels were harvested from 8 femoral trochlea from 4 sheep using the Acufex MosaicPlasty system (Andover, MA). Grafts were harvested perpendicular to the articular surface to a depth of 10 mm under constant saline irrigation. Power trephine grafts (n = 46, 2.7 P; n = 45, 4.5 P) were harvested by coupling the serrated trephine to a standard orthopaedic nitrogen powered drill. Manual punch grafts (n = 41, 2.7 M; n=33, 4.5 M) were harvested by malleting the punch to the required depth, minimizing rocking, and only slightly turning the punch on removal. Five 40-mum-thick fresh cartilage sections oriented perpendicular to the articular surface were obtained from each graft and then stained with Syto 13 and ethidium bromide vital stains, and the proportion of live cells per field and physical damage were compared between groups. Masson's trichrome stain was used on paraffin-embedded histologic sections. Results: Power harvesting was technically more difficult and resulted in more gross and light microscopic damage to the osteochondral grafts. Chondrocyte viability was significantly greater for manual punch versus power harvesting of both graft sizes (P < .005). Chondrocyte viability was greater for 4.5 P versus 2.7 P grafts (P < .005), but no difference was found between the 2.7 M and 4.5 M groups (P = .357). Conclusions: Chondrocyte viability is significantly greater using manual punch versus serrated power trephines when harvesting osteochondral grafts for cartilage resurfacing procedures. Power trephines should not be used for this procedure. Clinical Relevance: This study shows that the original method (power trephine) of harvesting osteochondral grafts results in great loss of chondrocyte viability versus manual punch harvesting and should no longer be used.