Abstract
The saphenous nerve is classically described as innervating skin of the medial foot to the first MTP joint and thus is at risk in surgery to the medial ankle and foot. However, it has previously been demonstrated that the dorsomedial branch of the superficial peroneal nerve consistently supplies the dorsomedial forefoot, and therefore previous descriptions of the saphenous nerve maybe erroneous.
We undertook a cadaveric study to assess the presence and variability of this nerve.
21 cadaveric feet were dissected from a level 5 cm above the medial malleolus, and distally to the termination of the saphenous nerve. In 16 specimens (76%), a saphenous nerve was present, of which 14 were anterior to the saphenous vein. Two of 16 nerves terminated above the medial malleolus. Therefore, only 14 of 21 specimens (66%) had a saphenous nerve present at the level of the medial malleolus. In seven of these 14 specimens (50%), the nerve terminally branched before the level of the tip of the malleolus. The mean distance reached in the foot was 46mm. Only two nerves reached the forefoot, at 97mm and 110 mm from the ankle joint respectively. At the ankle, the mean distance of the nerve from the tibialis anterior tendon was 9mm, and the saphenous vein 1.2mm.
Discussion
Our study shows that the course of the saphenous nerve is highly variable, and when present usually terminates within 40mm of the ankle. Only 10% reach the first MTP joint. These findings are inconsistent with standard surgical text descriptions.
The saphenous nerve is at risk in distal tibial screw placement and arthroscopy portal placement, and should be included in local anaesthetic ankle blocks in forefoot surgery, as a small proportion of nerves supply sensation to the medial forefoot.
