Techniques in Functional Muscle Reconstruction of Full-Thickness Defects of the Abdominal Wall

Full thickness abdominal wall reconstruction following oncologic resection remains a complex reconstructive challenge. The standard technique of bridging mesh repair has extremely high rates of long-term recurrent hernia. Functional muscle transfer, often in combination with bridging mesh, addresses this challenge by providing vascularized muscle as a functional counterforce to intra-abdominal pressure. Oncologic safety, timing, and recipient nerve identification are important considerations. The purpose of the review is to summarize flap options, technical considerations, and outcome data for both pedicled and free functional muscle reconstruction of the abdominal wall. Options for innervated abdominal wall reconstruction generally include the latissimus dorsi and regional muscle flaps from the thigh: the vastus lateralis, gracilis, rectus femoris, and tensor fascia lata. Pedicled flaps such as the vastus lateralis offer the advantage of immediate innervation and decreased complexity compared to free tissue transfer but suffer from limitations in pedicle reach and non-synergistic innervation with the abdominal wall. The latissimus dorsi free flap benefits from a large surface area and the potential for synergistic innervation to the abdominal wall. The ability to harvest the muscle in the supine position facilitates transfer to the abdomen and avoids position change. The vastus lateralis flap has been described as both a pedicled flap with reach extending to periumbilical defects as well as a free flap to extend reach. This flap may be harvested alone or in combination with the ALT flap when skin coverage is necessary. The vastus benefits from excellent bulk and maintained function when performed as a pedicled flap but suffers from limitations in reach and orientation for many defects. The gracilis muscle is a thin flap that offers minimal donor site morbidity, excellent muscle excursion, and a reliable anatomy and has been described as both a pedicled and free flap for smaller defects. Several modifications are described to extend reach to the level of the xiphoid and increase the cross-sectional area for coverage. The rectus femoris may be used as a pedicled or free flap to reconstruct abdominal wall defects. However, given the functional morbidity in knee extension, the rectus femoris is generally not considered a first line option. The pedicled tensor fascia lata flap is suited for infraumbilical and lateral abdominal wall reconstruction whereas free tensor fascia lata flap has improved coverage of supraumbilical and larger defects in case reports in the literature. The TFL flap, similar to the vastus, provides acceptable donor site morbidity and muscle bulk, but is limited in its reach and coverage. Given the inordinately high rates of recurrent hernia in the setting of bridged mesh repair for complex full thickness defects of the abdominal wall, free or pedicled functional muscle transfer may be considered as an adjunct to bridging mesh, as it provides vascularized coverage, additional strength to the repair, and a functional counterforce to intra-abdominal pressure overtime.