Adductor Canal Block: A guide for Patients
This page provides important information about an adductor canal block (ACB), also known as a saphenous nerve block. This is a type of injection of local anesthestic commonly used to help reduce pain during and after knee surgery (for example a total knee replacement), or some types of ankle surgery.
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 region of the saphenous nerve running down the inside of the thigh, and is sometimes able to see the nerve itself. Around 2/3 of the way down the thigh is often the best spot for this injection to be performed.
​
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.
Depending on the type, strength and amount of local anaesthetic injected, this block may last from several hours to several days.
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.
​
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 saphenous 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.