Medial Branch Blocks
A medial branch block (MBB) is another technique that falls under facet joint injections. It is a diagnostic injection that targets the medial branch nerves, which are small nerves that carry pain signals from the facet joints in the spine to the brain.
Facet joints, located in the neck, mid-back, and lower back, can become irritated or arthritic, leading to chronic back or neck pain. By injecting a local anesthetic (and sometimes a steroid) into all of the medial branch nerves at the same time, the block can:
Help confirm whether the facet joints are the true source of pain (diagnostic purpose)
Who Benefits from a Medial Branch Block
A medial branch block may be recommended if you have:
- Chronic neck, mid-back, or low back pain not relieved by other treatments
- Pain that worsens with certain movements (twisting, bending backward, or prolonged standing)
- Tenderness over facet joints in the spine
- Suspected facet joint arthritis or degeneration based on imaging or clinical exam
What to Expect
- Preparation: Typically no major preparation is needed, though you may be asked to avoid food or drink for a few hours if sedation is used.
- Positioning: You will lie face down on a procedure table.
- Imaging Guidance: Fluoroscopy (X-ray) or ultrasound is used to guide the needle safely to the medial branch nerves.
- Injection: After numbing the skin, a thin needle is placed near the target nerve, and contrast dye is injected to ensure the medicine covers the medial branch nerves. Then, a small amount of local anesthetic (and sometimes a steroid) is injected.
- Duration: The procedure usually takes 15–30 minutes.
- Outpatient: Patients go home the same day.
After the Procedure
- The patient will rest in the recovery area for 20-30 minutes, where the physician will ask the patient to perform some movements or activities that would usually provoke the pain. This assessment is done in order to determine if the medial branch nerve block has reduced the patient’s pain.
- The medial branch nerve block is designed to interrupt the pain signal being carried by the medial branch nerves supplying a specific facet joint. Because of this, patients may feel complete or partial pain relief during the first 4 to 6 hours after an injection. They may also feel no pain relief during this time (anesthetic phase).
- Diagnostic Value: Depending on the amount of pain relief the patient has during the first 2 to 3 hours after the injection, the patient may be a candidate for a radiofrequency ablation (RFA) procedure to try and provide longer term pain relief. Patients must report at least 80% improvement in their pain during the first 2 to 3 hours after the injection to be considered a candidate for radiofrequency ablation.
- Steroid Effect (if used): If a steroid is included, it may reduce inflammation and provide extended relief over several days.
- Temporary Side Effects: Mild soreness or numbness at the injection site is common.
Recovery and Aftercare
- Activity: Rest the day of the injection; normal activities can usually be resumed the next day.
- Monitoring Pain Relief: Keep track of how much relief you experience and for how long—this information is critical for your doctor to determine next steps.
- Driving: Avoid driving for several hours if sedation was used.
- Next Steps: If pain relief is short-lived but significant, your doctor may recommend repeating the block or moving forward with radiofrequency nerve ablation for longer-lasting relief.
Risks and Considerations
Medial branch blocks are generally safe, but possible risks include:
- Temporary soreness, bruising, or swelling at the injection site
- Mild allergic reaction to the medication
- Infection or bleeding (rare)
- Very rarely, nerve injury