Flow-Through Lateral Arm Flap With Vein Grafting for Repairing Circumferential Thumb Soft-Tissue and Segmental Vascular Defects.

Background: Circumferential soft-tissue loss of the thumb and vascular defects are among the most challenging problems in microsurgical reconstruction. Methods: We present the case of a 15-year-old male patient who sustained a thermal crush injury to the thumb, resulting in complete circumferential loss of skin and soft tissue with segmental defects of both the proper digital arteries and veins. After thorough debridement, reconstruction was performed with a free lateral arm flap based on the radial collateral artery. The flap was designed in a flow-through configuration: its proximal pedicle was anastomosed to the superficial branch of the radial artery, and its distal end to the remnant of the dorsal digital artery, thereby bridging the arterial defect while perfusing the flap. Because the venae comitantes were too small for venous repair, a Y-shaped vein graft was harvested from the forearm to reestablish distal outflow. Results: The flap and the thumb pulp survived completely, with satisfactory contour. At 1-year follow-up, flap sensory recovery was confirmed, and 2-point discrimination of the thumb pulp was 3 mm. The thumb achieved functional key pinch and contralateral-matched grip strength, despite mild interphalangeal joint limitation (20-degree flexion). Conclusions: This case highlights both the potential and the limitations of flow-through lateral arm flap in digital reconstruction and underscores the importance of tailoring flap selection and vascular strategies to the unique challenges posed by circumferential thumb defects.