[Emergency reconstruction of traumatic dynamic muscle defects using functional superficial vastus lateralis chimeric perforator flap based on descending branch of lateral femoral circumflex artery].

Objective: To investigate the feasibility and clinical outcomes of emergency reconstruction of traumatic dynamic muscle defects using functional superficial vastus lateralis chimeric perforator flap based on descending branch of lateral femoral circumflex artery.

Methods: A retrospective analysis was conducted of 10 patients with traumatic dynamic muscle defects treated between March 2020 and April 2024. There were 8 males and 2 females, aged 23-52 years (mean, 36.7 years). Injuries included 7 cases of Gustilo type ⅢB forearm trauma (2 with flexor muscle group defects, 3 with extensor muscle group defects, and 2 with combined flexor and extensor muscle group defects), 1 case of right first metacarpal defect with concomitant thenar muscle and skin defect, 1 case of complete transection of the right upper arm musclecutaneous nerve extracted from the biceps brachii muscle, and 1 case of Gustilo type ⅢC lower-limb trauma with extensor hallucis longus and toe extensor defects. Soft tissue defects ranged from 10 cm×8 cm to 36 cm×11 cm. Preoperative musculoskeletal ultrasound of the contralateral side was used to measure cross-sectional area, length, and pennation angle of the target muscles. Based on these parameters, anterolateral thigh flaps combined with one or two superficial vastus lateralis muscle segments were designed and transplanted to the recipient sites. The grafts were used to cover wounds, reconstruct major missing muscle groups, and were fixed in place. Vascular and neural anastomoses were performed simultaneously with repair of bone and soft tissue injuries to restore limb perfusion and function. Postoperative evaluation included musculoskeletal ultrasound, electrophysiology, and dynamic assessment of muscle strength during follow-up.

Results: All transplanted muscles and flaps survived primarily without vascular or neural complications. All the 10 patients were followed up 10-38 months, with an average of 22.8 months. The muscle strength recovery reached M₅ in 6 cases, M₄ in 3 cases, and $M_{3^{+}}$ in 1 case. Patients achieving M₄ or above regained their original work capacity; limb contours were symmetrical, with no joint deformities, and patients achieved effective ranges of motion; functional recovery included the ability to push or lift weights of 2-30 kg, perform opposition, and achieve grasping function. All flaps were soft and lustrous, and the protective sensation restored in all patients. There was no discomfort in the donor site and knee joint. Musculoskeletal ultrasound showed that the average cross-sectional area of the transplanted muscles increased by 4%-66% in 10 cases at 1 month after operation, and the ratio of the average cross-sectional area of the transplanted muscles in contraction and relaxation was 1.37±0.16 in 7 cases at 6 months after operation. Electrophysiological examination showed that motor potential could be detected in 8 cases at 2 months after operation, and then the amplitude increased gradually, and 2 cases were not detected.

Conclusion: Emergency reconstruction of traumatic dynamic muscle defects using functional superficial vastus lateralis chimeric perforator flap based on descending branch of lateral femoral circumflex artery achieves near-normal muscle strength recovery and effective joint motion. This technique allows for reconstruction of one or two major muscle groups as clinically required.