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Medial branch blocks

A medial branch block is an injection that numbs the small nerves supplying a facet joint in the spine. It helps confirm whether that joint is a source of your pain, and because anti-inflammatory medication is usually included, it can also provide lasting relief in its own right.

Facet joints are the small paired joints at the back of the spine that allow it to bend and twist. Each is supplied by tiny nerves called medial branches. If a facet joint is generating pain, numbing its medial branches should reduce that pain — briefly, and specifically.

Diagnosis and treatment together. The local anaesthetic answers a question — is this joint responsible? — by producing a clear window of relief in the hours after the injection. Anti-inflammatory medication is usually included as well, and this is what can settle an irritable joint for considerably longer. Many people get relief lasting weeks to months from the block itself; for others the value is a clear diagnostic answer that guides the next step. Both outcomes are useful.

Why it is often done twice. A single block can mislead. Placebo response is common, and a proportion of people report relief from a block that has not, in fact, targeted the source. Performing two blocks on separate occasions — sometimes using anaesthetics of different durations — reduces the false positive rate considerably. This matters when longer-lasting treatment is being considered.

What counts as a positive result. A substantial reduction in your usual pain during the expected window — commonly taken as at least 80% relief. Partial or ambiguous relief is a genuinely useful answer too; it may point to more than one pain source.

How likely are facet joints to be involved? It varies by region and population. Facet-mediated pain is more commonly identified in the neck, particularly after whiplash-type injury, than in the low back. Dr Martin will explain the likelihood in your case based on your history and examination rather than on averages.

On the day. You lie face down. Skin is cleaned and numbed. Under X-ray guidance, fine needles are placed against bone at defined targets and a small volume of local anaesthetic, usually with anti-inflammatory medication, is injected. Most people describe pressure rather than pain. You will be asked to record your pain levels over the following hours — this record is the result of the test, so it matters.

Risks. Whilst pain procedures are generally safe and well tolerated, all procedures carry risks. The specific risks relevant to you and your procedure will be discussed with you, and written information provided, before you decide to proceed.

Afterwards. Do not drive yourself home if sedation was used. Return to normal activity the next day. Any longer-lasting benefit from the anti-inflammatory component typically develops over the following days. Bring your pain record to your follow-up.