A study of skin flap advancement as a function of undermining.

An experimental model using piglets and strain gauges was used to measure the effect of undermining on the tension required to advance skin flaps. There was no simple relationship between undermining and wound-closing tension. In this model, wide undermining of broadly based flaps was not mechanically advantageous. Progressive undermining of narrow skin flaps, however, resulted in a continued decrease in advancement tensions. When a widely undermined, broadly based flap was progressively narrowed, measured advancement tensions decreased and approached zero. Forces involved in wound closure are discussed, and some possible mechanisms for these experimental findings are proposed.