Is reversed venous flow safe in free-flap transfer? A dilemma with the radial forearm flap

The distally based radial artery forearm flap has become our workhorse flap for hand and finger coverage, relying on reversed or retrograde venous outflow through the venae comitantes. Free-flap transfer, however, has been used by us only with antegrade venous anastomoses. This study was intended to determine if a single retrograde venous anastomosis would be adequate for flap viability. Six groups of saphenous flaps were developed in New Zealand White rabbits. In situ flaps compared antegrade with retrograde venous outflow in groups 1 and 2. Microvascular venous anastomoses with antegrade or retrograde outflow were compared in groups 3 and 4. Free-flap transfer with antegrade or retrograde venous outflow was compared in groups 5 and 6. No significant differences in survival was found between groups 1 and 2. A significant difference in survival (p = 0.025) was found between groups 3 and 4, but technical differences make these groups incomparable. Significantly better survival (p = 0.014, chi-squared test) was found in group 5 with antegrade outflow versus group 6 with retrograde outflow.