The anatomical and neurophysiological basis of the sensate free TRAM and DIEP flaps

Recent developments in autogenous breast reconstruction using the rectus abdominis myocutaneous free flap include attempts to reinnervate the flap tissue. We have carried out anatomical studies to determine the nature of abdominal-wall cutaneous innervation, with particular emphasis on the harvesting of sensate flaps. Dissections were performed on four embalmed and 12 fresh human cadavers (32 sides). The lowest five intercostal nerve trunks were identified and traced to the lateral border of the rectus sheath. A detailed dissection of the intramuscular course of the nerves and associated vasculature was performed. The relationship of the nerves to the vascular perforators used for rectus abdominis myocutaneous flaps was determined visually, and confirmed histologically. In contrast to previous studies, we show that nerves supplying cutaneous sensation can travel with both medial and lateral vascular perforators. In order to confirm clinically useful innervation, the abdominal flap skin of five patients undergoing TRAM flap reconstruction was stimulated electrically, and sensory recordings were made directly from the related intercostal nerve just prior to flap harvest. These studies represent, to our knowledge, the first clinical application of neurophysiological techniques to outline the perforator neurosomes of flaps based on the deep inferior epigastric vascular axis. We provide the first comprehensive study of abdominal-wall innervation with regard to sensate free-flap harvest. Our dissections show complex patterns of abdominal skin innervation that have not been previously described. The implications for sensate free TRAM and DIEP flap reconstructions, as well as the potential for more accurate inclusion of innervated flap skin, are discussed.