Fluoroscopic Guided Thoracic Medial Branch Block – Technique and Overview

Name of Procedure

  • Diagnostic Thoracic Medial Branch Block (TMBB)
  • Therapeutic Thoracic Medial Branch Block (TMBB)

Sample Opnote

Goal

To block and/or administer medications to the medial branch nerves that innervate the facet joints of the thoracic spine.

Indications

A diagnostic medial branch block might be performed to ameliorate pain from facet joints temporarily by using local anesthetic agents. The temporary block provides diagnostic value because a temporary relief in pain can help to determine if the treated facet joints are the source of the patient’s pain. This in turn can be used as part of a double comparative set of diagnostic blocks to move onto a radiofrequency ablation of the medial branch nerves.

A therapeutic medial branch block might be performed to ameliorate pathology around the medial branch nerves themselves, such as if a patient develops neuritis of the medial branch nerves after radiofrequency ablation/rhizotomy.

Contraindications

  • Common contraindications
  • Posterior fusion at the same levels as the target facet joints (ie, avoid L4-L5 facet treatment in a patient with a fusion at L4-L5) (…)

Anatomy

First, see our common spine anatomy overview to understand [bony structures], [facet joint naming] and [nerve root naming].

A “medial branch” technically refers to the medial branch of the dorsal ramus of a spinal nerve. This medial branch also innervates the multifidus muscle, which is of particular importance when performing a medial branch ablation.

Source: https://www.ncbi.nlm.nih.gov/pmc
/articles/PMC2684949

The source/path/naming/innervation of the medial branch nerves and their target injection sites can be confusing so a few key points should be kept in mind:

  1. Each facet joint is innervated by 2 medial branch nerves. In the lumbar spine, a joint is innervated by a branch from its top level and from the level above it. For example, an L4-L5 facet joint is innervated by a branch from the L3 and L4 spinal nerve.

L4-L5 facet in red. L3 and L4 originating branches in green going to innervate that joint.

  1. The medial branch nerves run over the junction of the transverse process (TP) and superior articulating process (SAP) on the posterior side of the spine, at ONE LEVEL BELOW where it originates.
    1. See the L3 branch circled in green: to block the medial branch from L3 you target the TP and SAP at L4.
    2. Note how that branch innervates the L3-L4 joint and continues down to innervate the L4-L5 joint (red). So a block at the L3 level affects two joints.
    3. Likewise for the branch from L4, you block at L5.
  2. Now, put together the originating branches and their target sites to determine how to block a specific facet joint:
    1. To block the medial branch nerves that innervate the L4-L5 facet joint, you would target the junction of the TP and SAP at L4 and again at L5.
  3. Note this common pattern extends to multiple levels. To block 3 joints (L2-L3, L3-L4, L4-L5), your target sites will be at L2, L3, L4, L5. Note that at L3 and L4, you are getting two half joints at once, which simplifies our procedure.

Cervical notes:

  1. The shorthand for the cervical spine generally works also: To block the C3-C4 joint you would block nerves at C3 and C4, which is nice and simple.
  2. One exception is that the C2-C3 joint is innervated only by the medial branch from C3, which is called the third occipital nerve and can be blocked on C2.
  3. In practice you’ll often block multiple facets like C2-C3 and C3-C4, which means you end up blocking C2, C3, C4 anyway.

Equipment/Skills

See our disposables/equipment article for “core” supplies that are common to all procedures. Highlights below:

  • Core Equipment
    • c-arm, c-arm compatible bed
  • Core Disposables
    • Procedure tray. As outlined in the above link, core supplies include a pointer, syringes for subcutaneous local, syringe for injectate, drape.

Special items and suggested setup for this procedure (see quick guide video above for example tray prep):

  • For lumbar medial branch blocks:
    • 22g x 5” quincke needle (a 3.5” needle can also be used in most patients but might not be long enough in some patients)
    • 8cc local anesthetic (1% lidocaine or 0.5% bupivacaine) in 10cc syringe as primary injectate
    • 3-5cc 1% lidocaine in 5cc syringe with 25g x 1.5″ hypodermic needle for subcutaneous anesthetic
  • For cervical /thoracic medial branch blocks:
    • 25g x 1.5″ hypodermic needle as your primary needle
    • 5cc local anesthetic (1% lidocaine or 0.5% bupivacaine) in 10cc syringe as primary injectate
  • For radiofrequency ablation:
    • RF cannula and probe with RF machine. (2 cannulas and 1 probe will allow for placement of a second cannula, while the prior one is ablating)
    • 3cc 1% lidocaine in 3cc syringe
    • 10cc 1% lidocaine in 10cc syringe with 25g x 1.5″ hypodermic needle for subcutaneous anesthetic

Landmarks and Patient Positioning

Position the patient in a basic prone position so that the bottom of the c-arm can go under the table below the area of the spine that is being treated.

Technique

For the sake of this tutorial we will assume we are treating the T9-T10, T10-T11, T11-T12 facet joints on one side, which means we have targets at the junction of the SAP and TP at T9, T10, T11, T12.

Steps:

  1. Obtain an AP or oblique/scotty dog view of T12, which will be the first target.
  2. Use your pointer to set an insertion site just above the TAP/SAP junction of T12. Insert your hypodermic needle right above the target and simply use a “down the barrel” approach to go straight down to the target.
  1. Once on bone, confirm your depth on a lateral view
    1. Confirm that you do not appear to be beyond the transverse process or at the depth of the neuroforamina.
  1. Repeat steps 1-3 for each level being treated. (Remember to level of the vertebral body at the level that you’re targeting)

Tips

  1. ANATOMICAL NOTE: As you progress up the thoracic spine the medial branch nerves site more lateral on the transverse process so you’re target is a bit lateral compared to lumbar levels.
  2. NEEDLE CHOICE: The thoracic spine is fairly superficial in many thin patients, so you can often get to it with a basic 25g x 1.5″ hypodermic needle.
    1. This way you don’t have to use a quincke needle, and since you’re just using a 25g you probably don’t need to anesthetize the skin (it’s the same needle you would use to anesthetize so instead of doing 2 pokes with the same needle, just do the one poke).
    2. Also, you probably don’t need a bent needle since you’re traveling a short distance.
  3. COUNTING LEVELS: In the thoracic spine it can get confusing which level you’re at if you don’t have a frame of reference:
    1. In the example above, after injecting at T12, leave the needle there while placing the pointer at T11: This way you have a needle sitting at T12 (to act as a frame of reference) while pointing at T11.
    2. You can keep continuing this as far up as needed even when you no longer see the bottom or top of the rib cage.
  4. DEPTH AND SAFETY: If you enter skin right on top of the TP and go “down the barrel” till contacting TP, it is unlikely you can move to a dangerous depth.
    1. This means you probably don’t need a lateral after every image. As soon as you contact bone, you’ll know you’re at your target.

Sample Images

References

General

Cervical

Radiofrequency