Avoiding Denervation of Rectus Abdominis in DIEP Flap Harvest: The Importance of Medial Row Perforators

Background: The deep inferior epigastric artery (DIEA) perforator flap for breast reconstruction spares rectus abdominis muscle and has low donor-site morbidity. However, abdominal wall weakness and bulge remain significant complications, with damage to the motor innervation of the rectus abdominis postulated as a cause. This study describes the relationship between the nerves supplying rectus abdominis and perforators, based on a thorough cadaveric study and review of the literature. Methods: Twenty hemiabdominal walls from fresh and embalmed cadavers were dissected, mapping the course of the nerve and vascular supply of rectus abdominis. Results: The infraumbilical segment of rectus abdominis was innervated by T9-L1, with four to seven nerve branches entering rectus abdominis from its lateral border (12 cases) or posterior surface (93 cases). Each nerve entered a nerve plexus running with the most lateral branch of the DIEA, before running with arterial perforators into rectus abdominis. Nerves entered rectus muscle more medial than the lateral row perforators (83 percent of cases), with the medial branches of the DIEA devoid of these nerve branches. Conclusions: The nerves innervating rectus abdominis are at risk during the raising of a DIEA perforator flap. These nerves enter the posterior surface of rectus abdominis and run with the most lateral branch of the DIEA and its perforators. Damage to these nerves may denervate rectus abdominis muscle and contribute to donor-site morbidity. As medial row perforators were not related to these motor nerves, these perforators are ideal for inclusion in DIEA perforator and transverse rectus abdominis myocutaneous flaps.