Medial Branch Nerve Blocks

A medial branch nerve block is a minimally invasive injection procedure that involves injecting a small amount of a local anesthetic, with or without a corticosteroid, near the medial branch nerves – the small nerves near the facet joints of the spine that carry pain signals from the joints to the brain.^,

The injection aims to block the pain signals transmitted through the medial branch nerves and produce targeted pain relief.^,

Goals of Medial Branch Blocks

The primary purpose of medial branch blocks is to diagnose or pinpoint pain originating from a facet joint(s) and guide further treatment if a positive response is seen.^,

• Diagnostic: Significant pain relief following the anesthetic injection suggests that the facet joints are involved, while lack of pain improvement indicates they are likely not the main contributor to pain.^,
• Treatment planning: A positive response to medial branch block injections also indicates that a patient will likely benefit from medial branch radiofrequency ablation (RFA) treatments that involve creating heat lesions on the nerves to prevent long-term pain signaling.^,

RFA treatments are preferred as they offer longer pain relief (6 to 12 months) and are not associated with the potential risks linked to repeated corticosteroid use.

See Radiofrequency Ablation (RFA) Side Effects and Risks

Less commonly, medial branch block injections are used therapeutically after a positive diagnosis and involve injecting a combination of an anesthetic and a corticosteroid for sustained pain relief (2-4 months).^,

When Medial Branch Blocks are Recommended

Medial branch blocks are used in the diagnosis of injuries and/or medical conditions that are known to cause inflammation of the facet joints, including^,:

• Facet joint osteoarthritis
• Spinal osteoarthritis
• Degenerative spondylolisthesis
• Rheumatoid arthritis
• Ankylosing spondylitis
• Scoliosis

As a treatment, medial branch blocks are typically considered after first-line therapies such as oral medications, primarily non-steroidal inflammatory drugs (NSAIDs), and physical therapy are tried for at least 3 months.

When Medial Branch Blocks May Not Be Recommended

Due to an increased risk of complications, medial branch blocks are contraindicated in the following circumstances^,:

• Active systemic infection
• Local infection around the procedure site
• Bleeding disorders
• Pregnancy

Additionally, patients are advised to communicate any known allergies or sensitivities to the drugs used in medial branch block procedures with their doctor, and to discuss possible alternative medications or interventions.

How Medial Branch Blocks Treat Facet Joint Pain

Two medial branch nerves innervate each facet joint, and they communicate pain signals originating from the spine to the brain.

These nerves are enclosed by a fibro-osseous canal (a canal formed by bone and soft tissue), and injecting medication into this canal allows the drug to adequately surround the nerve, blocking the pain signals transmitted by the nerve.

Number of Medial Branch Injections Needed

It is recommended that patients undergo two diagnostic medial branch block procedures due to the high potential for false-positive (placebo) responses from a single block. The second injection should be performed 2-3 weeks later to provide sufficient time for the effects of the first block to dissipate.

Effectiveness of Medial Branch Blocks

Multiple studies have demonstrated significant pain reduction after diagnostic medial branch blocks in patients with spinal pain. The outcomes of these studies show:

• More than half of the patients experience at least 80% improvement in pain after a successful diagnostic medial branch block.  
• If two medial branch blocks independently confirm facet joint pain at the same spinal level, there is approximately a 60% chance of achieving significant and lasting pain relief with RFA treatment of those medial branch nerves.

Therapeutic medial branch blocks that combine an anesthetic and a corticosteroid are generally not considered effective because studies have shown that they do not provide more pain relief than a placebo injection.  

Differences Between Medial Branch Blocks, Facet Joint Injections, and Epidural Steroid Injections

Epidural, facet, and medial branch injections share a common goal of alleviating inflammation and spinal pain. However, the type of injection used depends on the specific nature of the pain.

The following table lists the similarities and primary differences between these 3 common injection techniques.^,

In general, medial branch blocks are primarily diagnostic, and facet joint injections and epidural steroid injections are therapeutic interventions.^,