The saphenous nerve and its relationship to the nerve to the vastus medialis in and around the adductor canal: an anatomical study.

BACKGROUND: Recently, ultrasound-guided saphenous nerve blocks within and distal to the adductor canal have shown success. However, a potential side effect is an unintentional block of branches of the nerve to the vastus medialis resulting in undesired motor weakness.
METHODS: We dissected 40 embalmed cadaver thighs to determine the course and relation of the saphenous nerve to the nerve to the vastus medialis. Measurements were taken between various landmarks, and descriptive statistics were used to present the collected data.
RESULTS: In 72.5% of specimens, the most distal visible branch of the nerve to the vastus medialis pierced the muscle proximal to the site where the saphenous nerve crosses the anterior surface of the superficial femoral artery to become medial to the vessel.
CONCLUSION: Knowledge of this anatomy may help establish a safe region in preventing motor blockade when performing saphenous nerve blocks.