Flow-through flaps: a review of current knowledge and a novel classification system

Flaps have long been recognized as an essential tool for soft-tissue reconstruction. Flaps range in complexity from local to free and perforator flaps and can include a variety of composite tissues. The concept of a flow-through flap, in which both the proximal and the distal ends of the vascular pedicle of a free flap are anastamosed to provide blood flow to distal tissues, was first described by Soutar et al. in 1983. An uninterrupted arterial flow was established by Soutar et al. between the external carotid and distal facial artery via a radial forearm flap for head and neck reconstruction (Soutar et al., Br J Plast Surg 1983;36:1-8). Shortly thereafter, Foucher et al. were the first to report the reconstruction of an extremity with a simultaneous vascular defect by utilizing a radial forearm flow-through flap (Foucher et al., Br J Plast Surg 1984;37:139-148). The utility of the flow-through flap is now well established, and its indications for use continue to grow. The principle advantage of this flap is that it provides the opportunity for a single stage composite reconstruction of both soft tissue and vascular defects, making it particularly useful in the reconstruction of ischemic extremities and defects from oncologic ablations. Improvements in microsurgical equipment and techniques are making early difficulties with these flaps irrelevant, giving plastic surgeons opportunities to become more creative in the choices and uses of flow-through flaps. The literature consists mostly of case reports and series. The nomenclature used to describe the types of flow-through flaps is confusing and inconsistent. The purpose of this article is to provide an organized review of flow-through flaps and to classify these flaps based on their inflow, outflow, and the nature of their vascular conduit. Additionally, we have included a discussion on the physiology of these flaps, reviewed the current literature, and summarized the various types of flow-through flaps in a reference guide that can aid in flap selection.