The unfavorable anatomy of vastus lateralis motor nerves: a cause of donor-site morbidity after anterolateral thigh flap harvest.

Background: The anterolateral thigh flap is a popular reconstructive option, with a major advantage being its low donor-site morbidity. However, donor-site morbidity following anterolateral thigh flap harvest does occur, with postulated causes including damage to muscle, deep fascia, and the motor nerves to the vastus lateralis. No anatomical studies have yet described the relationship of these motor nerves to the vascular pedicle of the anterolateral thigh flap.

Methods: Thirty-six human cadaveric thighs underwent dissection studies, and the innervation of the vastus lateralis and the relationship of the nerves to the descending branch of the lateral circumflex femoral artery were documented. Variations were recorded.

Results: The nerve to the vastus lateralis branches extensively before entering the muscle, with four to seven nerves identified per thigh. Two particular variations of the nerve anatomy are uniquely susceptible to damage: where the motor nerve passes through the vascular pedicle itself or passes between perforators supplying the flap. At least one unfavorable variation was present in 28 percent of cases.

Conclusions: The nerves innervating the vastus lateralis are intimately related to the vascular pedicle of the anterolateral thigh flap. These nerves may be damaged during flap harvest and may contribute to donor-site morbidity after anterolateral thigh flap surgery.