Patterns of flap loss related to arterial and venous insufficiency in the rat pedicled TRAM flap

Vascular supply to the contralateral portion of the conventional transverse rectus abdominis musculocutaneous (TRAM) flap (zone IV) may become comprom ised, resulting in partial flap loss and requiring segmental excision. The etiology of this necrosis is not clear. This study determines skin necrosis patterns on a superiorly pedicled caudal TRAM flap during conditions of ve nous and arterial insufficiency, and determines whether cutaneous venous ou tflow can sustain a flap with venous insufficiency. Twenty-eight adult male Sprague-Dawley rats underwent superior pedicled TRAM flap elevation, and t he zones were marked on the skin paddle. The animals were divided into four groups: control (group A, N = 6), arterial ligation (group B, N = 6), veno us ligation (group C, N = 8), and venous ligation with cutaneous venous out flow (group D, N = 8). After 10 days, the skin paddle was photographed and the areas of necrotic skin were measured. Results showed that group 8 (sele ctive arterial ligation) had 51.7 +/- 2.8% and 40.0 +/- 2.0% skin necrosis In zones I and II respectively. Zone I necrosis was significantly greater i n group 8 compared with the control (p < 0.05), Group C (selective venous l igation) resulted in 73.8 +/- 16.4% and 93.8 +/- 33.4% skin necrosis in zon es III and IV respectively. This necrosis was significantly greater compare d with the control (p < 0.001). Group D rats' lateral skin necrosis compare d significantly less with group C (p < 0.001). These results demonstrate th at the patterns of flap necrosis in rat TRAM flaps with poor arterial inflo w differ from those with venous stasis. Necrosis of the contralateral porti on (zone IV) of human TRAM flaps may be related to problems with venous sta sis; thus, a cutaneous venous outflow may prevent this problem.