Femoral Nerve Block: A guide for Patients
This page provides important information about a femoral nerve block (FNB). This is a type of injection of local anaesthestic commonly used to help reduce pain during and after hip surgery (for example a total hip replacement), or some types of lower leg surgery. This nerve block routinely causes reduced sensation across the front of the thigh, and may cause temporary reduction in muscle strength in the front of the thigh. These are normal and short-lived effects of the FNB.
The Process
This injection can be performed with you either awake, sedated or under anaesthetic. Your doctor will use an ultrasound machine to identify the femoral nerve running through the groin.​
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Local anaesthetic may be injected into the skin around this area if you are awake. Your doctor will then pass a special needle to the area around the nerve under ultrasound guidance, and inject local anaesthetic near the nerve.
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Depending on the type, strength and amount of local anaesthetic injected, this block may last from several hours to around 24 hours.
Risks
Almost all medical care and procedures carry some degree of risk of something not going according to plan, and it's important to be aware of this beforehand. Your anaesthetist is always best placed to provide information about the risks of anaesthesia specific to you and your upcoming surgery. The risks listed here are generic and not tailored to you and your circumstances. There are also multiple other less frequently encountered side effects/complications which are not listed here, to avoid providing an overwhelming list.
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1. Failure of the block. Normally this block works well, but on occasion has little or no effect
2. Nerve damage. Very rarely either temporary or permanent nerve damage to the femoral nerve occurs.
3. Infection resulting from this injection is incredibly rare
4. Bleeding resulting from this injection is incredibly rare
5. Local Anaesthetic Systemic Toxicity (LAST) occurs when local anaesthetic makes its way into the blood circulation, and can cause complications with the heart and brain.