Analysis and Optimization of the Rhombic Flap Wound Closure

Objective: 1) Develop a hyperelastic computational model of skin viscoelastic properties for analysis of wound closures, and 2) Apply the model to variations of the rhombic skin flap to quantify closure force vectors and optimize wound closure tension.

Method: A computational model employing the finite element method was created to simulate skin defect closure employing rhombic transposition flaps. Variables of transposition angle, flap width, and tissue undermining were analyzed. Outcome measures of tissue stress, strain, and wound distortion were evaluated and optimized for a standard defect.

Results: A second order Yeoh hyperelastic model was fit to previously published experimental skin data with good approximation of observed properties. In the analysis of transposition flap closures of the 60 to 120 degree rhomboid defect, the model suggests that a biomechanically ideal flap design is constructed with distal flap angle of 30 degrees, as is employed in the Webster flap, with the donor site near margin oriented parallel to the short axis of the defect, as in the traditional Limberg flap. This configuration minimizes tissue stress and strain and most evenly distributes wound tension across the closure line.

Conclusion: The model quantitatively demonstrates several recognized principles of the rhombic flap. Square defects, as compared with rhomboid defects, close with lower tissue strain, but form a larger standing cutaneous deformity. The Webster flap best distributes wound tension across the incision line, and the Dufourmental modification alters the closure force vector.