Adductor Canal Block
The adductor canal is found medially in the mid thigh. The canal is formed by the fascial planes of 3 different muscles. The most clinically relevant muscle is the sartorious muscle. The anterior aspect of the adductor canal is formed by the sartorious muscle. The sartorius muscle is often described as a boat shaped structure on ultrasound. The adductor canal may also be described as being sub sartorial. In addition to the sartorius muscle the adductor canal is bordered by the vastus medals and the adductor longus muscles. Beginning at the proximal end of the adductor canal and
scanning distally, the femoral artery , also found in the adductor canal, can be seen on ultrasound "moving" medial to lateral along the posterior border of the sartorius muscle before diving deep to the sartorius in the distal thigh. In the mid thigh the saphenous nerve is most often located lateral to the femoral artery in the adductor canal between the sartorius and vastus medialis muscles although branches of the saphenous nerve do occasionally occur medial to the femoral artery as well. The saphenous nerve at the level of the adductor canal can be blocked for procedures involving the distal thigh, femur, knee and the medial aspect of the lower leg. The adductor canal block is often performed with or without a sciatic nerve block for ACL reconstruction and total knee arthroplasty.
Image showing adductor canal (AC), Femoral Artery (FA)
compressed Femoral Vein (FV), Sartorius Muscle, Adductor Longus and Vastus Medialis
The adductor canal block should be performed near the mid thigh level. The goal is to place 10-20ml of local anesthetic lateral to the femoral artery in the adductor canal defined as the space lateral to the femoral artery between the sartorius and the vastus medialis muscles. The medial side of the femoral artery may be accessed by hydrodissection anterior to the femoral artery. Approximately 5-10ml of local anesthetic is placed medial to the femoral artery. Local anesthetic spread around the artery should be confirmed by ultrasound visualization.
Facts, Tips and Tricks
The saphenous nerve is mostly sensory and thus preserves much of the motor function of the quadriceps muscle and allows for effective rehab in the post operative period. It is still necessary to assess patient muscle strength and stability prior to ambulation post operatively as a fall can be catastrophic
Attention should be placed on the orientation of the femoral artery to the sartorius muscle. The femoral artery will dive deep laterally to the sartorius muscle as you examine more distally in the thigh. As you scan the femoral artery cephalo-caudally the artery seems to “move” along the posterior margin of the sartorius. Take note of where the femoral artery is in relation to the sartorius muscle and consistently perform the block at the same level for more consistent results. Aim for the local to be injected where the femoral artery is just lateral to the midline of the sartorius muscle (in some cases it may be reasonable to perform the block where the adductor canal is best visible)
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