Mechanical Strain of the Trilobed Transposition Flap in Artificial Skin Models: Pivotal Restraint Decreases With Decreasing Rotational Angles.

BACKGROUND In transposition flaps, thicker tissue and higher degrees of rotation are associated with increased pivotal restraint; however, limited experimental data exist quantifying the degree to which these affect flap biomechanics. The use of artificial skin models in conjunction with digital image correlation technology allows for investigation into biomechanical properties of skin flaps. OBJECTIVE To quantify the effects of tissue thickness and rotational angles on pivotal restraint within transposition flaps using artificial skin models. METHODS Ninety degree bilobed and trilobed flaps were used to close defects in artificial skin models of increasing thicknesses. Digital image correlation was used to quantify strain. Quantitative and qualitative differences in strain were assessed in increasing flap thicknesses and between flap designs. RESULTS Increasing flap thickness was associated with decreasing strain. In the bilobed flap, increasing thickness was associated with displacement of the flap pivot point away from the distal flap edge. Comparatively, lower angles of rotation in the trilobed flap were not associated with migration of the flap pivot point. CONCLUSION Increased pivotal restraint observed in higher degrees of rotation is due to migration of the flap pivot point. This model supports the common practice of decreasing flap angles to compensate for pivotal restraint.