Abstract
Adductor canal block is a promising alternative to femoral nerve block for below-knee procedures because it allows for better preservation of the muscle strength of the quadriceps.1, 2 For lower leg, ankle, and foot procedures, the combination of adductor canal block and popliteal sciatic nerve block is commonly used. However, the needle insertion point differs between these two blocks. Moreover, adductor canal block is performed in the supine position, whereas popliteal sciatic nerve block can be performed in the lateral decubitus position. Performing the two blocks might be time-consuming. A recent report suggested that the adductor canal may induce sciatic nerve block.3 This indicates that the adductor canal is proximal to the sciatic nerve (Figure 1). Our approach combining adductor canal block and the lateral approach of sciatic nerve block at the midthigh level has almost the same needle insertion point in the supine position.
Keywords
adductor canal block; lower leg surgery; sciatic nerve block;
Adductor canal block is a promising alternative to femoral nerve block for below-knee procedures because it allows for better preservation of the muscle strength of the quadriceps.1, 2 For lower leg, ankle, and foot procedures, the combination of adductor canal block and popliteal sciatic nerve block is commonly used. However, the needle insertion point differs between these two blocks. Moreover, adductor canal block is performed in the supine position, whereas popliteal sciatic nerve block can be performed in the lateral decubitus position. Performing the two blocks might be time-consuming. A recent report suggested that the adductor canal may induce sciatic nerve block.3 This indicates that the adductor canal is proximal to the sciatic nerve (Figure 1). Our approach combining adductor canal block and the lateral approach of sciatic nerve block at the midthigh level has almost the same needle insertion point in the supine position.
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The knee is flexed, and the leg is abducted and externally rotated (Figure 2). First, the ultrasound probe is used to locate the midthigh level for adductor canal block. The adductor canal is the space surrounded by the sartorius, adductor, and vastus medialis muscles. In the canal, the saphenous nerve is located just lateral to the femoral artery. The probe is then moved medially. At the bottom of the adductor magnus muscle, the sciatic nerve usually can be found. We use 0.25% levobupivacaine 10 mL for adductor canal block and 20 mL for sciatic nerve block. For adductor canal block, the target is the saphenous nerve. Therefore, injection of local anesthetics exclusively around the saphenous nerve with 10 mL is enough for our approach.
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The location of the sciatic nerve at this level is deeper than that at the popliteal fossa. Therefore, it is more difficult to block the sciatic nerve than at the popliteal level. However, the needle insertion points for the two blocks are close to each other. This indicates that all procedures can be performed at roughly the same level. This is the main advantage of this method. If the identification of the sciatic nerve proves difficult, we can choose popliteal sciatic nerve block instead.
Børglum et al4 presented a similar approach combining saphenous nerve and sciatic nerve block. However, we sometimes need a convex ultrasound probe for the anterior approach because the location of the sciatic nerve is deeper. As for our approach, adductor canal block and sciatic nerve block usually can be achieved with a linear probe.
If vitalization of the sciatic nerve is not easy, the probe should be moved slightly toward the popliteal fossa because the sciatic nerve runs more superficially. We also recommend the use of nerve stimulation in combination with ultrasound guidance if needed.
Appendix A. Supplementary data
The following is the supplementary data related to this article:
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