Abstract: Objective To investigate the clinical effects of free anterolateral femoral flap repair of soft tissue defects of the skin of the extremities. Methods Eighteen patients with cutaneous soft tissue defects of the extremities, with defect areas ranging from 9 cm × 6 cm to 26 cm × 15 cm, were treated with flap transplantation. preoperatively and intraoperatively, the recipient area was thoroughly cleared, and the anterolateral femoral flap was excised to repair the wound and deal with the vascular crisis. All 18 cases were followed up for 6 to 12 months. All of the flaps were viable after surgery, and two of the free flaps had postoperative vascular crisis, which were viable after exploratory treatment. Conclusion The anterolateral femoral flap donor area is concealed, simple and practical, and can be used for repairing skin and soft tissue defects of the extremities with good clinical results. 1 Materials and methods 1. 1 Case data There were 18 cases in this group, 10 males and 8 females, with the minimum age of 20 years and the maximum age of 53 years. The defect area: maximum 26cm×15cm, minimum 9cm×6cm. cause of injury: 8 cases of car accident injury, 6 cases of heavy object crushing injury, 4 cases of machine strangulation injury, 8 cases with exposed bone or internal fixation plate screw, 12 cases with different degrees of tendon exposure or partial tendon necrosis. 1. 2 Surgical method The patient was placed in the supine position. The affected area was thoroughly debrided to remove dirt, necrotic and inorganic tissues, expose the arteriovenous vessels in the affected area, evaluate the vessels in the affected area, and trim them to healthy vessels if necessary. The flap was designed according to the size and shape of the recipient wound. Using the midpoint of the line between the anterior superior iliac spine and the outer edge of the patella as the key point, 2/3 of the flap length was designed far from the midpoint of the iliac-patellar line and 2/3 of the flap width was designed beyond the midpoint of the iliac-patellar line, and the flap was cut according to the design. The flap was first incised along the surface projection of the vascular tip as the flap tip, and the gap between the rectus femoris and the lateral femoral muscle was separated, and the descending branch of the lateral femoral artery was found on the superficial surface of the middle femoral muscle along the gap between the rectus femoris and the lateral femoral muscle. Dissect distally along the descending branch to find the first myocutaneous artery crossing branch, slowly separate the muscle along the direction of the myocutaneous artery and then find the 2nd and 3rd myocutaneous artery crossing branch downward to increase the blood supply of the flap, pull the flap back to the original position and temporarily suture it, then make a lateral incision of the flap and cut part of the broad fascia together, dissect inward under the deep fascia, cut and ligate the vessel at the distal end of the flap, and free the vessel proximally along the descending branch of the lateral rotator femoris artery. At the beginning of the flap, the vessels were cut at this point to form a free flap. The flap was transplanted to the recipient area, and the vascular tip vessels were anastomosed with the recipient vessels, and the area around the anastomosis was covered with soft skin tissue. The donor area was repaired with one-stage sutures or implants as appropriate. All 18 cases were followed up for 6 to 12 months. All 18 cases were followed up for 6 to 12 months, and the donor area wound healed well, and the flap in the recipient area survived well with satisfactory appearance. A. Anterolateral femoral flap design; B. Free flap area of 13 cm × 12 cm; revealing the perforating branch; C. Postoperative flap grafting. 3 Discussion 3. 1 Treatment of the trauma In clinical practice, in order to achieve better clinical results, the treatment of the trauma of the recipient area is directly related to the survival rate of the flap. The patient’s general condition should be prepared, and the patient should be adjusted to the best condition possible to tolerate flap grafting. ② Thoroughly remove foreign bodies, necrotic inactivation, and contaminated serious tissues from the trauma, liquefy tendons, and chisel away the exposed bone until the bone surface is fresh. 3. 2 Blood supply of the anterolateral femoral flap The anterolateral femoral flap is axially vascularized by the descending and penetrating branches of the spinolateral femoral artery, with the descending branches issuing 2 to 5 penetrating branches that cross the lateral femoral muscle and broad fascia and then enter the skin directly, and the descending branch of the spinolateral femoral artery to the lateral femoral cutaneous artery, which is divided into the penetrating branch of the musculocutaneous artery accounting for 59.8% and the intermuscular cutaneous branch 40. 6% [3]. Luo Lixiang et al [4] proposed that of the above 2 types, approximately 45% of specimens had a direct cutaneous perforator issuing from a high location, originating from the root of the descending branch of the lateral rotor femoral artery, or even directly from the lateral rotor femoral artery with a thin outer diameter, traveling on the surface of the lateral femoral muscle and crossing the broad fascia from the outside up to the skin. Therefore, there are three types of anterolateral femoral flap blood supply: myocutaneous artery penetration type, high skin branch type, and intermuscular skin branch type. The main trunk of the lateral rotor femoral artery is less variable, but the site of skin branch penetration is not constant, and there are high and low positions. When revealing and selecting the skin branch, the decision should be based on the actual area and shape of the flap and the thickness of the skin branch [5]. In this group, three flaps were selected because of the small area, and only the thicker high skin branch from the transverse branch was used, and the flap designed before excision was moved proximally upward, because the high skin branch is often a direct skin branch, and the transverse branch is used as the main trunk and anastomosis of the recipient area without dealing with the femoral nerve muscle branch, which obviously reduces the difficulty of separating the vessels and shortens the operation time, while blood flow is also ensured. For larger flaps, as many vascular skin branches as possible should be preserved to ensure adequate blood supply. In this group, there were 10 larger area flaps, including the high cutaneous branches from the transverse branch and the low penetrating branches from the descending branch. The dissection of the tip of the anterolateral femoral flap revealed that the high cutaneous branches from the transverse branch all crossed the anterior aspect of the lateral femoral nerve, and the 2nd, 3rd or more myocutaneous branches from the descending branch all crossed the posterior aspect of the lateral femoral nerve. If the main trunk of the lateral femoral artery is dissected, it is easy to form a situation in which the vessels and the lateral femoral nerve are intertwined [6]. In this case, if the anterolateral femoral flap is cut, the lateral femoral nerve must be severed if two to three myocutaneous artery branches are to be included. In this case, the lateral femoral nerve was preserved by the author. If there are two sets of sutured arteries and veins in the recipient area, the artery can be a branch of the main trunk of the recipient area, and the two sets of vessels can be anastomosed at the root of the transverse and descending branches, respectively. If there is only one set of anastomosed artery and vein in the recipient area, the root of the transverse branch and the root of the descending branch will be dissected and the artery and vein of the root of the transverse branch will be anastomosed with the branches of the descending branch, and the main trunk of the descending branch will be anastomosed with the vessels of the recipient area. 3. 4 Postoperative precautions After free flap grafting, close observation and meticulous care should be paid attention to, for which we have the following experiences: ① Keep the room temperature at 25℃, local heat preservation, and light the affected limb to keep it warm and improve blood circulation; ② Postoperative analgesia to avoid vasospasm due to pain and affect the blood circulation of the flap; ③ Wrap loosely to avoid compression affecting blood circulation; ④ Brake or elevate the affected part if necessary to promote ⑤ Postoperative application of anticoagulation, antispasmodic and vasodilatory drugs to prevent thrombosis; ⑥ Close observation of flap blood flow, if vascular crisis occurs, active treatment, including removal of part of the suture or reoperative exploration; ⑦ Postoperative drainage is unobstructed to prevent subflap hematoma formation.