ObjectiveTo explore the effectiveness of iliac myocutaneous flap pedicled with deep circumflex iliac artery (DCIA) on the repair of lower limb composite defect wounds with cavity. MethodsA retrospective analysis of 7 patients with lower limb composite defect wounds treated between March 2017 and September 2020 was conducted, including 4 males and 3 females, aged 24-58 years, with a median age of 37 years. The causes of injury were machine twisting injury in 2 cases, fall from height injury in 2 cases, and traffic accident injury in 3 cases. According to Gustilo-Anderson classification, there were 1 case of type Ⅲa, 4 cases of type Ⅲb, and 2 cases of type Ⅲc (combined with anterior tibial artery rupture); according to AO/Orthopaedic Trauma Association (AO/OTA) classification, there were 2 cases of type 42-C3, 2 cases of type 43-A2, and 3 cases of type 43-B1. The time from injury to admission ranged from 2 to 10 hours, with an average of 6 hours. Tibial bone defect and surrounding soft tissue defect with deep cavity were left after primary emergency debridement. In the second stage, according to the characteristics of the wound, the three-dimensional repair of the composite defect was designed with DCIA embedded iliac myocutaneous flap. The size of the iliac flap was 2.0 cm×2.0 cm×2.0 cm to 7.0 cm×3.0 cm×2.5 cm, and the size of the flap was 12.0 cm×8.0 cm to 21.0 cm×13.0 cm. The internal oblique muscle flap was harvested in size of 3.0 cm×2.0 cm×2.0 cm to 5.5 cm×4.0 cm×4.0 cm. The donor site was primarily closed. ResultsAll the flaps survived after operation, except for 1 case of partial necrosis of the flap edge, which healed after secondary skin grafting, and the donor and recipient wounds healed by first intention. All patients were followed up 16-24 months, with an average of 18 months. The broken end of the bone defect healed well, and the healing time was 8-10 months, with an average of 7.3 months. At last follow-up, the shape of the flap was satisfactory, the texture was soft, and there was no abnormal hair growth, pigmentation, and so on. Only linear scar was left in the donor site, and no complication such as abdominal hernia occurred. According to Paley fracture healing scoring system, bone healing was rated as excellent in 5 cases and good in 2 cases. The limb function was satisfactory, and full weight bearing was achieved at 12-16 months after operation. According to the lower extremity functional scale (LEFS), 6 cases were excellent and 1 case was good. Conclusion The iliac myocutaneous flap pedicled with DCIA is flexible in design and highly free in tissue composition, which can repair the composite defect wound of lower limbs with deep cavity in a three-dimensional way, and repair the limb shape and reconstruct weight-bearing function to the greatest extent.