Medial Branch Nerve Block

What It Is

The medial branch nerves are tiny sensory nerves that branch off the spinal nerve and carry pain signals from the facet joints at the back of the spine. A medial branch block is a precise injection of local anesthetic (numbing medicine) onto these nerves under live X-ray (fluoroscopy) guidance.

It’s primarily a diagnostic test: if temporarily numbing those nerves substantially relieves the pain, the facet joints they serve are confirmed as the pain source — and the patient becomes a candidate for the longer-acting radiofrequency ablation. The current standard is two separate medial branch blocks on different days; both must give substantial relief to confirm the diagnosis.

How It Works

Each facet joint receives sensory input from two medial branch nerves (one from above and one from below). Numbing both nerves temporarily silences pain signals from that joint. If the patient feels substantial relief during the duration the local anesthetic works, the facets are the pain source. If relief is partial or absent, the source is something else — disc, muscle, sacroiliac joint, etc. — and a different treatment direction is indicated.

Because no steroid is used (in the diagnostic version), the relief from a medial branch block is short-lived by design. The point is to confirm or rule out facet involvement before committing to a longer-acting procedure.

When It’s Used

A medial branch block is typically considered when:

• Clinical exam and history strongly suggest facet-mediated back or neck pain
• A trial of physical therapy, NSAIDs, and activity modification has been completed without lasting relief
• The patient is being considered for radiofrequency ablation and needs the diagnostic confirmation first
• An intra-articular facet injection has been tried and produced only short-lived relief

What to Expect

• The procedure takes about 15 to 30 minutes in a fluoroscopy suite at the pain management office or surgery center
• You lie face-down; skin is cleaned and numbed with local anesthetic
• The interventional pain physician places small needles at the medial branch nerves at the relevant levels under live X-ray, confirms position, then injects local anesthetic
• You’re asked to track your pain over the next several hours and report what percentage of relief you got — this determines whether radiofrequency ablation is the next step
• Most patients drive themselves home
• Two separate blocks (typically a few weeks apart) are usually required to confirm the diagnosis before proceeding to ablation

Risks and Limitations

• Bleeding / bruising. More relevant if you take blood thinners.
• Infection. Very rare with sterile technique.
• Temporary numbness. A small area near the injection site may be numb for a few hours.
• False-positive or false-negative results. No diagnostic test is perfect — this is why two separate blocks are usually required.
• Headache. Rare, and usually self-limited.

Why OSI Doesn’t Do This In-House

OSI does not perform medial branch nerve blocks in-house. They require live fluoroscopy and dedicated interventional pain training outside the OSI orthopedic scope. Patients who are candidates for a diagnostic block are referred to a trusted pain management physician we work with, with the relevant exam findings and imaging sent ahead.

OSI continues to manage the conservative side — physical therapy, medications, follow-up — so the procedure fits into a larger plan, not a one-off referral.

Next Steps

If you think you might be a candidate — or you just want a generalist read on whether this procedure is the right next step — schedule a spine evaluation at OSI or call (830) 625-0009. We will examine you, review imaging you bring with you, and either start a non-operative plan or coordinate the referral to a trusted pain management partner.