Adductor Canal / Saphenous

grays saphenous nerve IThe saphenous nerve is the terminal branch of the femoral nerve.   It courses distally along the superficial femoral artery and vein until approximately the distal third of the thigh.  At this point the artery and vein dive deep through the adductor canal.  The saphenous continues caudal where it passes through the vastoadductor membrane, a fascial plane deep to the sartorius muscle and adjacent to the vastus medialis, often referred to as Hunter’s Canal.  It emerges into the subcutaneous tissue between the sartorius and gracilis tendons where it joins the saphenous vein near the crease of the knee.  The saphenous nerve and vein travel together along the medial aspect of the lower leg and pass anterior to the medial malleolus.

At the level of the distal thigh, this block is used as augmentation (e.g. tourniquet coverage) of a sciatic block at the popliteal fossa for procedures of the distal lower extremity.  The saphenous can also be blocked at various locations below the knee (discussed in ankle blocks).  More recently authors have described performing a saphenous block more proximal in the thigh using ultrasound for post-operative pain management following surgical procedures involving the knee.

ADDUCTOR CANAL

Indications: Post-operative pain management of surgical procedures involving the knee

Patient Position: Supine, slight lateral rotation of the thigh

Transducer: High frequency linear array transducer (>7 MHz)

Transducer Orientation: Transverse view, short-axis image

Needle: 5cm B-Bevel block needle

Local Anesthetic: Up to 20 mL

Keys To A Successful Block: visualization of local anesthetic within the fascial plane deep to the satorius muscle and adjacent to the vastus medialis

adductor landmark and US image

SAPHENOUS NERVE BLOCK

Indications: Supplement sciatic block for procedures below the knee

Patient Position: Supine, slight lateral rotation of the thigh

Transducer: High frequency linear array transducer (> 7 MHz)

Transducer Orientation: Transverse view, short-axis image

Needle: 5 cm, B-bevel block needle

Local Anesthetic: 20 mL

Keys To A Successful Block: Visualization of local anesthetic within the fascial plane deep to the sartorius muscle

The patient is placed in the supine position with slight lateral rotation of the extremity (below left image).  At this level the saphenous can be identified using two methods.  The first involves finding the saphenous nerve which is adjacent to the femoral artery and vein in the mid-thigh, then scanning distally toward the knee.  In this distal thigh, the artery and vein will dive deep through the adductor canal, while the nerve will continue more superficially in the vastoadductor fascia between the sartorius (SAR) and vastis medialis (VM) muscles.  The second method involves starting in the distal thigh and locating the femur, then sliding the transducer medially until the saphenous nerve, sartorius and vastus medialis  muscles are identified.

saphenous distal thigh pre and post injection

 

 

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