At Hospital for Special Surgery, a saphenous nerve block may be used for pain control after surgery of the knee and foot. The saphenous nerve is a branch of the femoral nerve. It is purely a sensory nerve, that is, it conveys only sensory information and does not control any muscle in the leg. It transmits pain, temperature, and touch sensation from parts of the knee and along the inner aspect of the lower leg and foot.
Blocking the function of the saphenous nerve (a technique known as a saphenous nerve block) is one the methods used for controlling pain after knee and foot surgery. Another closely related method is the femoral nerve block. However, the femoral nerve innervates several muscles in the thigh, and blocking this nerve may result in temporary weakness of those muscles. In contrast, the saphenous nerve block would result in less muscle weakness, while providing similar degree of pain control. Some patients may benefit from a saphenous nerve block compared to a femoral nerve block, and the choice will be made between you and your anesthesiologist.
Prior to the placement of the block, you will be given sedation with intravenous medication. Your anesthesiologist will clean the skin with an antiseptic solution and, depending on the site of the injection, an ultrasound machine may be used to identify the saphenous nerve.
Local anesthetic is deposited around the nerve via a small needle. Pain relief is expected to last between 6 to 18 hours, depending on the mixture of local anesthetics used. As with any anesthesia procedure, there are risks and benefits associated with the saphenous block. Details will likely be included in the discussion of the anesthesia plan for you.
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