Objective To investigate the clinical effects of retrograde anterolateral thigh perforator flaps assisted with computed tomography angiography (CTA) in repairing skin and soft tissue defects around the knee or in proximal lower leg. Methods A retrospective cohort study was conducted. From May 2015 to October 2019, 17 patients with skin and soft tissue defects around the knee or in proximal lower leg were admitted to the Department of Orthopedics of Jizhong Energy Xingtai Mig General Hospital, including 12 males and 5 females, aged 16-65 years, with an average age of 35 years. The areas of skin and soft tissue defects after debridement ranged from 6.0 cm×3.0 cm to 15.0 cm×9.0 cm. The retrograde anterolateral thigh perforator flaps were designed according to the origin and distribution of the perforating branches in flaps and the length of the vascular pedicle examined with CTA and the condition of the wound to repair the wounds. The areas of resected flaps ranged from 6.5 cm×3.5 cm to 15.5 cm×9.5 cm. The wounds in donor sites of flaps were sutured directly or covered with medium-thickness skin grafts from healthy upper leg. The sources of the perforating branches in flaps were recorded. The lateral circumflex femoral artery, its branches, and the relative length of the vascular pedicle were compared between preoperative CTA detection and intraoperative observation. The survivals of the flaps were observed. At the last follow-up, the effects of flaps in repairing wounds were evaluated according to evaluation standard of efficacy satisfaction; the motion ranges of flexion and extension of the knee joint were measured, and the knee joint function was evaluated according to the Hohl knee joint function evaluation standard; the sensory function in the flap area was evaluated according to the sensory function evaluation standard formulated by the British Medical Research Council; the wound healing and the occurrence of complication affecting motor function of limb of flap donor sites was observed. Data were statistically analyzed with paired sample

test. Results The perforating branches in flaps originated from descending branches, oblique branches, and rectus femoris branches of lateral circumflex femoral artery in 7, 6, and 4 patients, respectively. The flaps with blood supply from descending branches, oblique branches, and rectus femoris branches of lateral circumflex femoral artery were type 1, 2, and 3 retrograde anterolateral thigh perforator flaps, respectively. The preoperative CTA examination of lateral circumflex femoral artery and its branches were consistent with those observed during operation. The relative lengths of vascular pedicles of type 1, 2, and 3 retrograde anterolateral thigh perforator flaps calculated after CTA examination were 0.32±0.13, 0.56±0.07, and 0.56±0.15, which were close to 0.35±0.12, 0.52±0.10, and 0.53±0.12 measured and calculated during operation, respectively (

=0.45, 0.80, 0.31,

>0.05). All flaps survived in 17 cases without vascular crisis. At the last follow-up, 16 patients were satisfied with effects of flaps in wound repair, with 1 patient feeling average about the effect; the flexion range of knee joint was 100-120°, and the extension range of knee joint was -2-0°; knee joint function was evaluated as excellent in 9 cases, good in 7 cases, and poor in 1 case; the sensory function of the flap area reached S₄ level in 2 cases, S₃ level in 8 cases, and S₂ level in 7 cases; the wounds in flap donor sites healed well; there was no adverse effect in motor function of limbs. Conclusions Retrograde anterolateral thigh perforator flap is an effective method for repairing skin and soft tissue defects around the knee or in proximal lower leg. Preoperative CTA examination can fully show the anatomical characteristics of the branches of the lateral circumflex femoral artery and the perforating vessels of each branch, which can guide preoperative flap design and operation, thus shortening operation time and improving flap survival rate, with good clinical effects.