Defining vascular supply and territory of thinned perforator flaps: Part I. Anterolateral thigh perforator flap

Background: The anterolateral thigh perforator flap is increasingly being used for trauma and reconstructive surgical cases. With the thinned flap design, greater survivability and a decrease in donor-site morbidity are observed. To increase our knowledge of the vascular territories in these flaps, an anatomic study was performed to determine pedicle number, location, and diameter; accompanying veins; vascular territory; and where surgical incisions can be made safely during thinning, as opposed to the "danger zone." Methods: Thirteen anterolateral thigh perforator flaps were harvested from seven adult cadavers. The largest perforator arteries were cannulated, and flaps were thinned to a thickness of 6 to 8 mm, with a 2.5-cm radius from the perforator retained. Vascular territories were quantified before and after thinning by nonradiographic and radiographic methods. A series of dyes were injected: red dye for skin (photography) followed by Omnipaque for the whole flap (radiography) before thinning, and blue dye for skin (photography) and lead oxide for the whole flap (radiography) after thinning. Pedicle locations were determined by ratios of anatomical landmarks. Danger zone measurements were derived at specific thicknesses using lateral radiographs of each flap. Results: In anterolateral thigh perforator flaps, the mean perforator artery diameter at the fascia level was 1.00 ± 0.08 mm (range, 0.84 to 1.11 mm) and the mean number of perforator arteries was 1.69 ± 1.03 (±SD). Perforator pedicles were located near the midpoint of the line between the anterior superior iliac spine and the lateral aspect of the patella in the vertical axis. The mean vascular territories were 256 ± 52.5 cm ² (photography) and 351 ± 72.8 cm² (radiography) in unthinned flaps and 211 ± 65.7 cm² (photography) and 289 ± 106.6 cm² (radiography) in thinned flaps. Differences in overall vascular territories after thinning were 83.3 percent (photography) and 81.8 percent (radiography) compared with unthinned flaps. Four respective vascular territory maps were drawn showing surgical territories using percentile confidence intervals (98th and 90th) and averages. From the skin at thicknesses of 4, 6, and 8 mm, the 98th percentile danger zones were 33 to 37 mm (proximal to distal), 30 to 35 mm, and 27 to 31 mm from the pedicle in the vertical axis, respectively; in the horizontal axis, they were 30 to 34 mm (medial to lateral), 28 to 31 mm, and 25 to 29 mm. Conclusions: These data define anterolateral thigh perforator flap pedicle location, number, and diameter before harvesting, surgical danger zones during thinning, and vascular territories after thinning. The authors' guidelines provide surgeons with anatomical vascular territory maps to design and harvest specific flaps for optimal results.