Facet Joint Injection

What is it?

Facet joints are small joints at the back of the spine, found on the left and right at every level. They guide bending and twisting movements and help carry load. With age or strain, these joints can develop wear and tear (osteoarthritis) and cause low back pain, neck pain or upper back and chest wall pain.

A facet joint injection places medication, under image guidance, into these joints or next to the small nerves that supply them. There are two main types:

• Intra-articular injection: local anaesthetic, sometimes with a corticosteroid, is injected directly into the joint.
• Medial branch block: local anaesthetic is injected next to the small nerves, called medial branches, that carry sensation from the joint.

When is it considered?

Facet joint pain is usually felt in the middle of the lower back, neck or upper back. It can spread to the buttock, around the shoulder blade or into the shoulder, but it rarely travels below the knee or down to the hand. Leaning back, twisting and standing for long periods can make it worse, and morning stiffness is common.

Symptoms and imaging alone cannot confirm the diagnosis: joint wear seen on an X-ray or MRI is not always the source of pain. That is why facet joint injections are mostly used for diagnosis. If the pain clearly eases after local anaesthetic is injected, the joints are likely to be the source.

Guidelines differ. The UK's National Institute for Health and Care Excellence (NICE) does not recommend spinal injections as a treatment for low back pain, but it accepts the medial branch block as a diagnostic step before radiofrequency treatment. An international, multispecialty consensus report also notes that the effect of steroid injections into the joint can be limited and short-lived for many people. The procedure is therefore considered as part of a longer-term treatment plan.

How does it work?

The local anaesthetic blocks pain signals from the joint, or from the nerve supplying it, for a few hours. How much your pain eases during this time gives important information about where it is coming from. When a corticosteroid is added to an intra-articular injection, the aim is to reduce inflammation around the joint.

If a diagnostic block clearly reduces the pain, radiofrequency treatment of the same nerves can aim for longer-lasting relief. To make the result more reliable, the block is sometimes done twice with medicines that act for different lengths of time.

Before the procedure

Your examination and imaging are reviewed together to decide which levels to treat. You and your doctor will plan how to manage any blood thinners. To make the diagnostic block easier to interpret, you may be asked not to take painkillers in the hours beforehand; check this with your doctor in advance.

Let the team know about any possibility of pregnancy, an allergy to medicines or contrast dye, or a fever. The aim of the procedure, possible risks and the alternatives are explained before you give your consent.

What happens during the procedure?

For the lower and upper back you lie face down; for the neck, lying face down or on your side may be used. After the skin is cleaned and numbed, fine needles are guided to the target joints or nerves under imaging. Several levels are usually treated in the same session.

For a diagnostic block, only a very small amount of medicine is used, so that it reaches the target nerve alone. Deep sedation is not usually given, because it can make it harder to judge the change in your pain. The procedure usually takes fifteen to thirty minutes.

After the procedure

You will be observed for a short time and can go home the same day. If you had a diagnostic block, you will be asked to score your pain from 0 to 10 at set times over the following hours and record it in a pain diary. Carefully trying the movements that usually provoke your pain during this time makes the result more meaningful.

Because the local anaesthetic can make your legs or arms feel temporarily numb or heavy, do not drive on the day of the procedure. The injection site may feel tender for a few days. You can return to your usual activities from the next day. Contact your doctor if you develop a fever, increasing pain or redness.

When might you notice results?

The local anaesthetic starts working within minutes and lasts a few hours; the diagnostic assessment is based on this period. If a corticosteroid was injected into the joint, the effect usually begins within a few days. How long it lasts varies: for some people it lasts several weeks, while others notice no clear effect.

The results help decide the next step. People who respond well to a diagnostic block may go on to radiofrequency treatment, while for those who do not, other sources of pain are investigated. To arrange an assessment, you can request a consultation.