Thin flaps are useful for reconstruction of exposed regions such as the face, neck and hand. However, the definition and classification of thin flaps differ among surgeons. Thus, we searched previous articles and discussed a new classification method for thin flaps. As a result, thin flaps can be classified anatomically, technically and temporally. These classifications can be mixed, and a new classification of “thin-type flap” and “thinned flap” was proposed. Moreover, “thinned flaps” can be separated into primary thinned flaps, secondary thinned flaps and multiple staged thinned flaps. For example, thin-type flaps include radial forearm flaps and SCIP (superficial circumflex iliac artery perforator) flaps. These flaps are naturally thin without the thinning procedure. The thickness of thin flaps is less than 1 cm. Primary thinned flaps have had fat tissues removed intraoperatively, and secondary thinned-flaps have been thinned before flap transfer, such as some delayed flaps and expanded flaps. Multiple staged thinned flaps include defatted flaps after transplantation.
