Lumbar medial branch block is a diagnostic test to ascertain whether pain in the lower back is arising from the facet joints (see facet joint syndrome for more on the facet joints) in the lumbar spine, that is the lowest section of the spine.
The test works by temporarily interrupting pain signals from this area transmitted to the brain via the medial branch nerves (that supply sensation from the facet joints), by injecting a small quantity of local anaesthetic directly to these nerves. Where pain is significantly reduced, this indicates that the facet joints are the source of the pain.
A lumbar medial branch block generally lasts for 24-48 hours, but in some cases it may continue to suppress pain for longer.
To accurately diagnose facet joint related pain, you may need two sets of lumbar medial branch blocks.
Lower back pain.
For a lumbar medial branch block (as a primarily diagnostic procedure), it is important to be able to reproduce the pain at the time of the procedure. For this reason, you should stop taking any pain medication around 5-6 hours beforehand.
If there is no pain on the day you are due to undergo a lumbar medial branch block, we may suggest postponing it to a later date.
You should avoid undergoing any other medical procedures, such as for example dental treatment or a colonoscopy, within 48 hours (before or after) of a lumbar medial branch block.
Please also let us know ahead of the procedure if…
- You are taking any antibiotics.
- You have a pacemaker or defibrillator.
- You have any known allergies.
- You are ill (in which case we may need to postpone the procedure).
You should also not drive yourself to or from the appointment, or drive in the 24-hour period immediately after the procedure.
The procedure generally takes no longer than 15-20 minutes (although we recommend allowing around one hour for the appointment).
You are asked to lie face down on theatre table, with a pillow placed under your stomach. An IV line is put in place in your arm or hand (for any medication needed so you remain comfortable during the procedure).
The injection site is then cleaned and numbed with a local anaesthetic and a thin needle is inserted at the injection site and then guided to the correct position using a mobile x-ray unit.
Before the anaesthetic is injected, a small quantity of contrast dye is introduced to check that the anaesthetic will get to the target area.
Once the procedure is complete, you will need to spend around half an hour under observation before being able to go home. While under observation you will be asked to see if you can reproduce the pain you normally feel, and let the doctor know if there has been any reduction in pain, and how much.
After the procedure you are able to return home. There is no restriction on day-to-day activities. In some (relatively rare) cases there may be some discomfort and/or bruising to the skin at the injection site. You will be asked to complete a 24-hour pain diary.
A lumbar medial branch block procedure is a relatively low-risk procedure – however all medical treatment comes with some level of risk. Possible complications may include…
- Pain at injection site.
- Allergic reaction to anaesthetic and / or contrast dye.