Biomechanics of A-to-T flap design.

OBJECTIVES/HYPOTHESIS: The objective of this study was to determine the vertical height, horizontal incision width, and extent of undermining that correlated with the lowest closure tension. STUDY DESIGN: Prospective, cadaver study. METHODS: Forty "A-to-T" flaps were made on the torso and lower extremities of fresh cadavers. Ten flaps each were designed at heights of three, four, and five defect radii. Closing tensions were measured for each of these flaps initially, followed by serial base extensions. Based on the information from these first flaps, 10 additional flaps were made at the optimal height and base extensions. These flaps were then serially undermined and tension measurements taken. RESULTS: Our results suggest that making the vertical height of the "A" twice the height of the defect yields a significant decrease in tension of closure when compared with a vertical height one and a half times the defect (P < .01), while increasing the height to two and a half times the defect height provides only a minimal further reduction in closure tension. Extending the base (horizontal) incision one defect diameter in each direction offers the greatest reduction in closing tension. Undermining up to three times the diameter of the defect offers progressive improvement in the tension of closure, while further undermining confers little additional benefit. CONCLUSIONS: Our findings indicate that the ideal A-to-T flap is designed to be twice the height of the original defect, with base extensions one defect diameter in each direction, and undermined to three times the diameter of the defect.