The effect of skin graft preparation on wound contraction

Both clinically and experimentally, full thickness skin grafts inhibit wound contraction better than do split thickness grafts. This occurs even if full thickness grafts are thinner than split grafts. Since inhibition of wound contraction does not depend on graft thickness alone, other differences should be sought between full and split grafts to explain this inhibition. One such difference is method of preparation. While full thickness grafts are cut with sharp dissection, split grafts are cut with mineral oil or with dermatome glue which is then stripped off. Both mineral oil and surface stripping in intact skin cause epidermal hyperplasia, more prominent in split grafts than in full thickness grafts. In this study, the effect of skin graft preparation on wound contraction and epidermal hyperplasia was tested. Seventy-four split thickness skin grafts were cut from Fischer rats with lubrication using mineral oil, Lubafax, normal saline solution or glue and a Padgett dermatome. Six full thickness grafts were treated with mineral oil. All grafts were placed on syngeneic rats; the area was measured with a planimeter, and biopsies were taken at zero, one, two, four, eight, 14 and 20 weeks. Mineral oil prepared split grafts lost 17.8 +/- 2.2 per cent area by one week, with a maximal loss of 38.8 +/- 4.8 per cent by four weeks. Split grafts cut with Lubafax, saline solution or glue plus drum dermatome lost similar area. Split grafts later enlarged as the rats grew, but in no group did split grafts surpass their original area. Full thickness grafts, even though treated with mineral oil, grew 3.9 +/- 4.3 per cent beyond their original area by four weeks and enlarged through 20 weeks. Histologic examination showed that all split skin grafts, regardless of surface preparation, had considerable epidermal hyperplasia and scarring in graft dermis and bed between one and four weeks. Thus, both skin graft contraction and epidermal hyperplasia occur independently of how grafts are prepared. The explantation of why full and split thickness grafts inhibit wound contraction differently must lie intrinsic rather than extrinsic to the skin.