A model of pressure distribution under peripherally secured foam dressings on a convex surface: does this contribute to skin graft loss?

Background: Successful skin grafting requires multiple factors for success. An even distribution of constant pressure exerted upon the graft is necessary for successful graft take. It is well known that excessive pressure on a graft causes ischemia and may result in the failure of graft take. The aim of this study was to demonstrate the variation in skin pressure (tension) on curved surfaces, particularly relating to apical pressure on such surfaces at standard atmospheric pressure.

Methods: A synthetic Sawbone skull model was used to determine skin tension over a curved surface. A 10-cm diameter circle was centered on the parietal eminence, the area of maximum curvature. Peripheral screws gave fixed reproducible points to secure the foam dressing. Open-cell VAC dressing foam was used and calibrated Tekscan sensors were used to determine pressure variation under the foam dressing.

Results: Five hundred pressure readings were obtained for the unscored foam, and an additional 500 for the cross-scored foam. In the unscored foam, the pressure under the dressing was significantly higher at the apex. Cross-scoring the foam reduced the pressure, with the greatest reduction being at the apex. The pressure under the foam dressing was maximal at the apical point (95% confidence interval).

Conclusion: Higher contact force at the apex of a curved graft bed may explain skin graft loss. Unequal pressure distribution can be reduced and equalized by scoring the foam.