Ultrathin Anterolateral Thigh Free Flap: An Adipocutaneous Flap with the Most Superficial Elevation Plane

Background: Although many efforts have been made to create thinner anterolateral thigh (ALT) flaps, their thickness varies among patients, and the flap may be still too thick to match shallow defects. The authors successfully harvested an ALT flap through the most superficial elevation plane, the superficial fat layer, which was useful to match the shallow defects.Methods: All patients who underwent ALT free flap reconstruction for upper and lower distal extremity defects were divided retrospectively into groups by ALT flap elevation plane: thin, above the deep fascia; superthin, at the superficial fascia; and ultrathin, through the superficial fat. Preoperative computed tomographic angiography and duplex ultrasonography planning were used for all patients. Anatomical characteristics of donor subcutaneous tissue and surgical details, including flap thickness, flap size, and incidence of flap necrosis were compared among the groups and between sexes.Results: The average deep and superficial fascial depths were 16.7 and 10.8 mm, 12.5 and 8.2 mm, and 9.1 and 5.6 mm (P < 0.05), and the average flap thickness was 5.8 mm, 7.9 mm, and 7.8 mm (P = 0.29) in the ultrathin, superthin, and thin ALT groups, respectively. No significant intergroup differences existed in flap size or complications. The deep and superficial fascia were located significantly deeper in female patients (9.4 and 6.0 mm in male patients and 14.9 and 9.6 mm in female patients, respectively).Conclusions: With precise preoperative planning, the most superficially elevated, ultrathin ALT flap can achieve optimal reconstructions of thin body areas. Female patients with thicker thighs and patients with a high body mass index would benefit from this flap.