Background: The perfusion of the transverse abdominal flap was studied by many authors but became better known after Hartrampf published his work on the TRAM flap (zones I-IV). However, the classic Hartrampf zones II and III were demonstrated by Holm et al to be reversed using fluorescent perfusion techniques. This gave significant weight to the suggestion that blood flow from the deep inferior artery travels to the ipsilateral side before crossing the midline. Our hypothesis is that the zones of perfusion and the vascular anatomy differ greatly between a single lateral perforator and a medial row perforator.

Methods: We utilized four- dimensional CT angiography to re-appraise the four zones of vascularity. A total of twenty transverse abdominal flaps were used for this study. These flaps were all harvested from fresh cadavers from the University of Texas Willed Body Program. Fourteen single lateral row perforators versus twenty medial row perforators were injected in order to determine the vascular territory in the zones of perfusion. Individual perforators were injected with Isovue contrast using a Harvard precision pump and each flap subjected to dynamic CT scanning using a GE Lightspeed sixteen slice scanner. Scans were repeated at 0.125ml increments (every 15 seconds) for the first 1 ml, then at 0.5ml increments (every 60 seconds) for the next 3 ml, thus giving us progressive CT images over time. Images were viewed using both General Electrics and TeraRecon systems, allowing analysis of branching patterns and perfusion flow.

Results: We found that medial perforators conform to the Hartrampf zones of perfusion (zone II is over the contralateral rectus muscle), and lateral perforators follow the Holm theory of perfusion (zone II is on the ipsilateral lateral region). Injection of a lateral row-based perforator flap gave a vascular territory that rarely crossed the midline.

Conclusion: Medial and lateral row perforators offer distinct and stereotypical zones of perfusion that have a significant impact on flap design and harvesting.