What is a cervical medial branch facet block and how is it performed?

Cervical Medial Branch Facet Block: Definition and Procedure

What It Is

A cervical medial branch block is a diagnostic and therapeutic injection procedure that targets the small nerves (medial branches) supplying the cervical facet joints to identify and treat neck pain originating from these joints. 1

The medial branches are sensory nerves that innervate the facet (zygapophysial) joints in the cervical spine. By blocking these nerves with local anesthetic, physicians can determine if the facet joints are the source of a patient's chronic neck pain. 1, 2

Why It Is Done

Diagnostic Purpose

• To identify facet joint-mediated pain when physical examination and imaging cannot reliably determine the pain source, as no physical findings consistently correlate with facet pain. 1, 3
• The procedure has a sensitivity of 54%, specificity of 88%, and positive predictive value of 81% for identifying cervical facet joint pain. 1
• Facet-mediated neck pain accounts for 36% to 67% of patients with chronic neck pain based on controlled studies. 2

Therapeutic Purpose

• To provide pain relief lasting an average of 14-19 weeks per injection in patients with confirmed facet-mediated pain. 4, 5
• Studies demonstrate that 83-93% of properly selected patients achieve significant pain relief (≥50%) with repeated blocks over 1-2 years. 4, 5
• The procedure serves as a prognostic tool before considering radiofrequency ablation, which is the definitive treatment for facet-mediated pain. 3, 6

Step-by-Step Procedure

1. Patient Selection Criteria

Before performing the block, patients must meet specific criteria:

• Axial neck pain (pain in the neck itself, not radiating significantly down the arm) that has persisted for more than 3 months. 3
• Failed conservative treatment for at least 6 weeks, including physical therapy and medications. 3, 7
• Pain that limits daily activities and affects quality of life. 3, 7
• Absence of untreated radiculopathy (nerve root compression causing arm pain/numbness), as facet blocks are not indicated for radicular symptoms. 7
• Physical exam showing cervical midline and paraspinal tenderness, limitation of cervical motion, and pain with extension/rotation movements. 3

2. Pre-Procedure Preparation

• Complete history and physical examination documenting the chronology, quality, intensity, distribution, and duration of pain, plus exacerbating/relieving factors. 1
• Review imaging studies (MRI or CT) to rule out other obvious causes of pain such as disc herniation, spinal stenosis, or tumor. 1, 7
• Obtain informed consent discussing risks, benefits, and the diagnostic nature of the procedure. 1

3. Procedure Technique

• Fluoroscopic (X-ray) guidance is mandatory to ensure accurate needle placement at the target medial branch nerves. 3, 7
• The patient is positioned prone (face down) or in a lateral position.
• The skin is sterilized, and local anesthetic is applied to numb the skin.
• Under continuous fluoroscopic visualization, a small needle is advanced to the waist of the articular pillar where the medial branch nerve crosses. 4, 2
• Typically 2-3 levels are injected on one or both sides, depending on the suspected pain levels. 8
• Approximately 0.5-1 mL of local anesthetic (usually bupivacaine 0.25%) is injected at each medial branch. 4, 8
• Some practitioners add steroid (e.g., 20 mg triamcinolone), though studies show no significant difference in outcomes between local anesthetic alone versus local anesthetic with steroid. 4, 5

4. Post-Procedure Assessment

• The patient is monitored for 15-30 minutes after the procedure.
• Pain relief is assessed immediately and over the following days to weeks. 4, 5
• For diagnostic purposes, the double-block technique is considered most reliable: performing blocks on two separate occasions using anesthetics with different durations of action to confirm facet-mediated pain. 1, 7
• A positive diagnostic block requires ≥80% pain relief and the ability to perform previously painful movements. 3, 6, 2

5. Follow-Up and Next Steps

• If the block provides significant temporary relief, it confirms facet-mediated pain and the patient may be a candidate for radiofrequency ablation (the definitive treatment that provides longer-lasting relief). 3, 6
• Therapeutic blocks can be repeated approximately every 3-4 months (average 3.5 times per year) for ongoing pain management. 4, 5
• Patients achieving good relief can expect significant improvement for 46-48 weeks per year with repeated blocks. 4

Important Caveats and Pitfalls

False-Positive Results

• False-positive rates range from 27% to 63% with single diagnostic blocks, which is why the double-block technique with ≥80% relief threshold is recommended for accurate diagnosis. 1, 7, 2
• Anesthetic leakage into adjacent structures can cause false-positive results by blocking unintended nerves. 3

Limited Therapeutic Value of Intra-articular Injections

• Medial branch blocks are superior to intra-articular facet joint injections for both diagnosis and treatment, as intra-articular injections have shown no long-term benefit over placebo. 7, 2
• The evidence specifically supports medial branch blocks, not injections directly into the facet joint itself. 7, 2

Patient Selection Errors

• The procedure should not be performed in patients with radiculopathy (arm pain from nerve root compression), as this indicates a different pain source requiring different treatment. 7
• Imaging must demonstrate no other obvious cause of pain such as disc herniation or spinal stenosis before attributing pain to facet joints. 7

Realistic Expectations

• While effective, medial branch blocks provide temporary relief averaging 14-19 weeks, not permanent cure. 4, 5
• Patients requiring frequent repeated blocks should be considered for radiofrequency ablation, which provides longer-lasting relief (typically 6-12 months or more). 3, 6