Course and Topography
The topography of the n. saphenus is closely related to the femoral vessels and the adductor canal.
- In the thigh: The nerve accompanies the femoral vessels (a. et v. femoralis). Together, they enter the adductor canal (Hunter's canal, canalis adductorius).
- Within the adductor canal: The nerve lies within the canal, bounded laterally by the m. vastus medialis, medially by the vastoadductor membrane (lamina vastoadductoria), and posteriorly by the m. adductor longus (superiorly) and m. adductor magnus (inferiorly).
- Exit from the canal: The saphenous nerve does not exit through the adductor hiatus (hiatus tendineus / adductorius). Instead, it leaves the canal through the anterior opening in the vastoadductor intermuscular septum (septum intermusculare vastoadductoria). According to anatomical variations, exit may occur through a single common opening or multiple separate openings.
- After exit: The nerve emerges beneath the m. sartorius and travels deep to the fascia toward the medial aspect of the knee. The n. saphenus and v. saphena magna travel together in the medial retromalleolar region.
Accomorting Structures
Along its pathway, the n. saphenus is associated with the following structures:
- Femoral vessels (a. et v. femoralis) — the nerve accompanies them in the thigh and within the adductor canal.
- Descending genicular artery (a. descendens genus) and its saphenous branch (r. saphenus a. genus descendens) — the nerve emerges through the anterior opening of the adductor canal alongside these vessels.
Innervation Territory
The saphenous nerve provides sensory innervation to the skin of the following areas:
- Leg: A narrow strip of skin on the posteromedial surface. On the medial side of the leg, its branches extend to the border with the anterior compartment.
- Foot: Its terminal branches supply the skin along the medial border of the foot, extending to the midpoint of the medial arch. The lateral border of the foot is supplied by the n. suralis, and the majority of the dorsal foot by branches of the n. fibularis superficialis.
Clinical Significance
Injury or entrapment of the saphenous nerve presents with the following clinical features:
- Adductor canal entrapment: Compression of the n. saphenus within the tight confines of the canal can cause paresthesias along the medial leg. Concomitant compression of the femoral vessels may cause ischemic pain in the leg and foot.
- Isolated lesion: Results in hypesthesia along the medial aspect of the leg and foot. A key diagnostic sign is the absence of motor deficits.
- Diagnostics: Electromyography (EMG) and nerve conduction studies (NCS) are the gold standards for assessing peripheral nerve injuries, including the n. saphenus.