|Level of blockade||Coverage distribution (Figure 145-1)|
|Saphenous nerve at various levels along its route||Anteromedial aspect of the lower leg distal to the level of the blockade, extending more or less down the medial aspect of the ankle and the foot|
Figure 145-1. Sensory Territory of the Saphenous Nerve Block
Reproduced from Hadzic A. The New York School of Regional Anesthesia Textbook of Regional Anesthesia and Acute Pain Management. Figure 40-1. Available at: www.accessanesthesiology.com. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.
The saphenous nerve is a purely sensory branch of the femoral nerve. It emerges in the inguinal area, travels in the femoral canal, deep to the sartorius muscle, along with the femoral artery and vein and the nerve to the vastus medialis (NVM), which gives branches along the way in the thigh. The saphenous nerve gives off some articular branches to the knee joint. In the lower leg, while traveling in proximity to the greater saphenous vein, it innervates the skin of the anteromedial aspect of the lower leg.
Figure 145-2. Anatomy of the Saphenous Nerve
Techniques have been described to block the saphenous nerve at every level along its route (Figure 145-3):
- In the inguinal area (perifemoral)
- In the femoral canal (using a subsartorial or transsartorial approach)
- At the medial femoral condyle
- As a field block below the knee, from the anterior tibial tuberosity to the anterosuperior edge of the muscle belly of the gastrocnemius (Figure 145-4)
- In the lower leg (paravenous approach)
- At the ankle, anterior to the medial malleolus
Figure 145-3. Multiple Approaches to Saphenous Nerve Blockade
Adapted with permission from Benzon HT, Sharma S, Calimaran A. Comparison of the different approaches to saphenous nerve block. Anesthesiology. 2005;102(3):633–638.
Figure 145‐4. Below‐the-Knee Field Block
(1) Tibial tuberosity; (2) medial head of the gastrocnemius. A field block is performed by infiltrating the subcutaneous tissues from the tibial tuberosity toward the gastrocnemius. The success rate is poor. Beware not to lacerate the saphenous vein that runs near the anterior aspect of the medial head of the gastrocnemius.
Anesthesia or analgesia of the medial aspect of the lower leg or the ankle, in combination with a popliteal sciatic block, for surgery of the lower leg, the ankle, or the foot.