ObjectiveTo explore the feasibility and accuracy of modified three longitudinal and five transverse method in locating perforating branches before anterolateral thigh perforator flap (ALTP) repair.MethodsBetween January 2019 and December 2019, 41 patients with skin and soft tissue defects were repaired with ALTP. There were 31 males and 10 females. The age ranged from 18 to 61 years, with an average of 32 years. The soft tissue defects were caused by trauma in 38 cases, and the time from injury to operation was 3-7 days, with an average of 4 days. The wounds left after excision of scar contracture deformity because of burn in 3 cases. Soft tissue defects located at upper limbs in 16 cases and lower limbs in 25 cases. The size of soft tissue defects ranged from 10 cm×4 cm to 25 cm×12 cm. Before operation, zonesⅠ, Ⅱ, Ⅲ, and Ⅳwere formed on the anterolateral thigh by modified three longitudinal and five transverse method. The perforating branches were detected in these four zones by Doppler ultrasound, and the skin flaps were designed according to the wound area. The perforating branches were explored during operation, and the distribution and types of perforating branches in each zone and the relationship between perforating branches and lateral femoral cutaneous nerve were observed. The ALTP with the size of 12 cm×5 cm to 30 cm×10 cm was used to repair the wound, and the donor site was sutured directly or repaired with the flap. ResultsA total of 117 perforating branches were detected in 41 patients before operation, and 111 perforating branches were found during operation, with a false positive rate of 5%. The probability of perforating branches in zonesⅠ, Ⅱ, Ⅲ, and Ⅳ were 56%, 73%, 76%, and 66% respectively, and the false positive rates were –9%, 7%, 16%, and 4%, respectively. All perforating branches located near the trunk of lateral femoral cutaneous nerve, especially in posterolateral area. There were only 1 perforating branch in 6 cases, 2 perforating branches in 12 cases, 3 perforating branches in 10 cases, and 4 perforating branches in 13 cases. The main types of perforating branches in zonesⅠ, Ⅱ, Ⅲ, and Ⅳ were transverse perforating branches, oblique perforating branches, descending perforating branches, and descending perforating branches, respectively. Partial distal necrosis occurred in 2 cases and complete necrosis occurred in 1 case after operation, and the wounds were repaired with skin grafts. The remaining 38 flaps survived successfully, and the wounds and the incisions of donor sites healed by first intention. All patients were followed up 3 to 12 months, with an average of 6 months. The appearance and texture of the skin flap were acceptable, and linear scar remained in the donor site.ConclusionIt can simply locate and distinguish the perforating branches and better protect the lateral femoral cutaneous nerve by using the modified three longitudinal and five transverse method before ALTP repair.