We report the use of a free flap with proximal arterial reconstruction to cover Gustilo III B skin defect wounds of the lower extremity. A 22-year-old man was injured in a motorcycle accident, sustaining a right femoral fracture and right leg joint open fracture. CT images revealed obstruction of the superficial femoral artery（SFA）, and ultrasonic examination demonstrated reduced distal blood flow. To cover the bone soft tissue defect of the right foot joint, free latissimus dorsi musculocutaneous flap transplantation was performed on the 70th day after injury with SFA reconstruction by a large saphenous vein graft. Right leg joint fixation was performed five months after surgery. He was able to walk one year after surgery. Evaluating the hemodynamics requires ultrasound examination or angiography, and ultrasound examination is useful, minimally invasive and highly accurate for assessing hemodynamics. We assessed the hemodynamics of the recipient vessel before and after reconstruction of the SFA by ultrasound, and confirmed hemodynamic improvement. Peripheral limbs may be preserved even in cases with decreased blood flow due to arterial injury. In cases with poor circulation, we should reconstruct the vessels whenever possible.