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Chapter 32E. Ultrasound-Guided Saphenous (Subsartorius/Adductor Canal) Nerve Block

The saphenous nerve:

A. Innervates the lateral aspect of the knee

B. Sends infrapatellar branches to the knee joint

C. Supplies only skin and subcutaneous structures

D. Typically innervates the skin at the entire medial side of the foot to the base of the first toe

B is correct. The saphenous nerve sends infrapatellar branches to the knee joint.

A is incorrect. The saphenous nerve does not innervate the lateral aspect of the knee. The infrapatellar branches innervate the anteromedial part of the knee. Anterolaterally the knee is innervated by the lateral femoral cutaneous nerve, the common peroneal nerve, and the femoral nerve branch to the lateral vastus muscle.1

C is incorrect. The saphenous nerve also supplies deeper structures. Cadaver studies have verified nerve endings form the saphenous nerve in the medial and ventral parts of the joint capsules of the ankle and the talocalcaneonavicular joint and the periosteum of the medial malleolus.2–4

D is incorrect. In the majority of cases, the saphenous nerve extends only to the midfoot.4,5

Which of the following statements is true regarding the course of the saphenous nerve?

A. There is no consistent landmark for the saphenous nerve in the lower leg.

B. The saphenous nerve lies in the adductor canal in close proximity to the femoral artery and vein.

C. The saphenous nerve lies posterior to the medial malleolus before it terminates in several fine branches.

D. The saphenous nerve pierces the fascia lata to become subcutaneous posterior to the tendon of the gracilis muscle.

B is correct. The saphenous nerve lies in the adductor canal in close proximity to the femoral artery and vein.

A is incorrect. The saphenous nerve lies in close proximity to the great saphenous vein in the lower leg. For the paravenous approach at the level of the tibial tuberosity the great saphenous vein serves as an important landmark.6

C is incorrect. The saphenous nerve follows the great saphenous vein in its entire course and therefore also courses anteriorly to the medial malleolus.

D is incorrect. The saphenous nerve consistently pierces the fascia lata and becomes subcutaneous between the tendons of the sartorius and gracilis muscles. On the other hand, the infrapatellar branch from the saphenous nerve shows much more variation in relation to the distal part of the sartorius muscle ...

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