Effects of Tissue Component Volumes on Vascular Resistance in Free Flaps

Background A successful free flap transfer is achieved, in part, by having a thorough understanding of vascular anatomy and blood flow dynamics. We previously reported that vascular resistance differs by type of free flap. To test the hypothesis that the difference reflects the proportion of tissue components within free flaps, we calculated blood flow and vascular resistance for free flaps in which we determined the volume of each tissue component. Methods Measurements and calculations were made for 40 free flap transfers performed at our hospital: 7 radial forearm flaps, 14 anterolateral thigh flaps, and 19 rectus abdominis myocutaneous flaps. Results The vascular resistance of free flaps was inversely related to the volume of each tissue component. Univariate regression analysis revealed that muscle volume correlated most closely with resistance (r = 0.881), followed by skin (r = 0.622), and fat (r = 0.577). Multiple regression analysis confirmed the relationship between combined muscle and fat volume and resistance (R² = 0.865). Conclusions A strong inverse correlation exists between vascular resistance and combined muscle and fat tissue volume in flaps. It may be helpful to consider these relationships when making decisions regarding choice of free flap and recipient vessels.