The Lower Extremity Blocks

In contrast to the upper extremity, the nerves going down the lower extremity are not so neatly packaged. For the arm, we can usually anesthetize the brachial plexus with one injection. There are some blocks that miss a specific nerve (like the musculocutaneous or intercostobrachial), but for the most part, hand, wrist, and forearm surgeries can be handled quite easily. In contrast, the nerves innervating the lower extremity don't run together. To achieve surgical anesthesia, we often have to target two nerves in different compartments of the leg. A combined popliteal-saphenous block is sufficient for foot or ankle procedures. Both a femoral and sciatic block are necessary to get all aspects of the knee (though we usually only do the femoral so we don't delay physical therapy). For patients with trauma, positioning for the blocks can be tough because we need to get to different aspects of the leg; sometimes, we have to be creative and sacrifice ergonomics to block the patient who is in too much pain to move.

The truth is, lower extremity blocks do not have to be in the armamentarium of every anesthesiologist. A single shot spinal or epidural catheter can achieve many of the anesthetic or analgesic requirements, though it has other undesired consequences like affecting the nonoperative leg. I've come to respect lower extremity blocks, though, because a lot of leg, ankle, and foot surgeries happen in patients with many medical comorbidities. Patients requiring a knee replacement are often older and obese. Diabetics get foot and ankle complications that require amputation. Not all these patients are the lowest risk for a general anesthetic, and knowing how to do a good leg block can be the optimal anesthetic plan.

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