What Is US-guided Carpal Tunnel Injection?
No specific preparation is needed. You might feel numbness or pins and needles in your hand for up to 1 hour after the injection, and driving is not recommended during this period. It is generally advised that you bring someone with you who can drive you home.
US-guided Carpal Tunnel Injection Overview
You will be taken into the scanning room. You will either be lying on a scanning bed or sitting down with your hand on a table or bed in a comfortable position. The sonographer will apply gel over your wrist and take images using ultrasound.
You will be able to ask any questions at this time. The skin over your wrist is cleaned with antiseptic liquid. A small needle is passed through your skin directly into the carpal tunnel using ultrasound images to guide the placement of the needle. A small amount of corticosteroid (or ‘steroid’) and local anaesthetic (usually just a few millilitres) is then injected, and the needle removed. Most people are surprised by how quick and easy the procedure is.
The wrist and hand should generally be rested completely for 6 hours, followed by minimal use for between 1 and 3 days.
Before and After the Procedure and the Risks
Before the Procedure
No specific preparation is needed.
After the Procedure
Immediately after the injection, you might have numbness in your hand from the local anaesthetic. It is recommended that you do not drive until the numbness has settled or have someone drive you home after the procedure.
The most common after effect is a temporary increase of your symptoms over 1, 2, or even 3 days. The corticosteroid does not start working for at least 24 hours and sometimes up to 7 days.
Symptoms from nerves generally take longer to respond to corticosteroid than symptoms relating to muscles or joints. During this time, the normal symptoms might continue or, occasionally, are worse. A major flare of symptoms generally indicates a local reaction to the injected medication or to having the needle. Anti-inflammatory medication, rest (use of a splint) and the application of cold packs is recommended. If the reaction is persistent, then you should seek medical attention, as it might be an infection, although this is unlikely.
Procedure Risks
This is a very safe procedure with few significant risks, but occasionally problems are experienced.
An allergic reaction to the corticosteroid or local anesthetic is uncommon. Allergies to antiseptic liquid and dressings/band aids can also occur.
Some people find that the injection gives them pain relief for a few months, but the symptoms can then return. There are no concerns about having another injection, but ongoing injections over a long period are not recommended. Although the exact risk of multiple injections is not known, most doctors would advise against having the injection more than three times a year to avoid tissue atrophy (thinning and scarring) within the carpal tunnel.
There is a very small risk of infection, which is minimized by the doctor carrying out the procedure under clean conditions. The injection will not be administered if there is broken skin or infection in the skin over the carpal tunnel area.
There is a remote risk of the needle passing through the nerve, which would cause severe pain or nerve symptoms. Although this is extremely remote, it is a known risk of injections carried out close to nerves.
