Abstract
The saphenous nerve is classically described as innervating skin of the medial foot extending to the first MTP joint and thus is at risk in surgery to the medial ankle and forefoot. However, it has previously been demonstrated by the senior author that the dorsomedial branch of the superficial peroneal nerve consistently supplies the dorsomedial forefoot, leading to debate as to whether the saphenous nerve should routinely be included in ankle blocks for forefoot surgery. We undertook a cadaveric study to assess the presence and variability of the saphenous nerve.
29 feet were dissected from a level 10 cm above the medial malleolus, and distally to the termination of the saphenous nerve. In 24 specimens (83%), a saphenous nerve was present at the ankle joint. In 5 specimens the nerve terminated at the level of the ankle joint, and in 19 specimens the nerve extended to supply the skin distal to the ankle. At the ankle, the mean distance of the nerve from the tibialis anterior tendon and saphenous vein was 14mm and 3mm respectively. The mean distance reached in the foot was 5.1cm. 28% of specimens had a saphenous nerve that reached the first metatarsal and no specimens had a nerve that reached the great toe.
The current study shows that the course of the saphenous nerve is highly variable, and when present usually terminates within 5cm of the ankle. The saphenous nerve is at risk in anteromedial arthroscopy portal placement, and should be included in local anaesthetic ankle blocks in forefoot surgery, as a significant proportion of nerves supply the medial forefoot.
