Super-thin ALT flap elevation using preoperative color doppler ultrasound planning: Identification of horizontally running pathway at the deep adipofascial layers

Introduction: Presently, super-thin ALT flap, which is elevated above the superficial fascial plane, is gaining popularity. Although there is a huge demand for thin flaps for various types of extremity reconstruction, the technique for ALT flap thinning remains controversial. In this study, we investigated the distance and vector between penetrating points of perforators in deep and superficial fascia using color duplex and clinical measurement to suggest a reliable super-thin flap elevation technique. Materials and Methods: From June 2018 to February 2020, 44 patients with various types of defects who were treated using super-thin ALT flaps were enrolled; 69 surgically detected perforators were analyzed. All patients’ flap outcomes and characteristics of the perforators were analyzed. In addition, the effects of patients’ body mass index (BMI) and thickness of super-thin flap were evaluated. Results: The average traveling length of perforator at the deep adipofascial layer (DAL) was 2.43 cm, and the vector of traveling was randomly arranged. The mean thickness of super-thin ALT flap was 6.8 mm. The thickness of super-thin flap was not significantly correlated with patients’ BMI (ranged from 17.4 to 34.2 kg/m²; p = 0.183). Conclusion: The novel elevation technique for super-thin ALT might be useful, as evidenced by perforator traveling distance and vector in DAL. Preoperative color duplex ultrasonography is helpful to detect the running course of the perforators during elevating the flap. This anatomic concept must be considered to obtain the reliability of the super-thin ALT flap.