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Lumbar medial branch blocks

Updated: May 22, 2022

Problem facts

-Diagnosing facet joint arthropathy as pain generator

-Traumatic/degenerative/inflammatory

-36% in young adults, >89% in >70yo (have changes)

-Indication – axial spine pain poorly controlled or unexplained

-Physical and neurological findings are not conclusive

-Imaging findings are not conclusive (inc SPECT)

-Facet takes 25% of axial and 40-65% of rotational forces

-RFs – Age, obesity, body mechanics, overuse, microtrauma

-Often associated with disc degeneration

-C2-3 if associated with headache

-L4-5, L5/S1 most common

Palpation shows tender transverse and paravertebral


Diagnosis

-Pain localised over back in non-dermatomal radiation pattern

-Back of buttock and thighs (rare below the knee)

-Neurology is unlikely as primary generator

-Though can have associated osteophytes/cysts

-Palpation shows tender transverse and paravertebral

-Pain exacerbated by extension and rotation

-Kemp test (Sens <50% and Spec <66%)


Imaging

-Plain film sensitivity and specificity is poor (even oblique views)

-MRI can show degen changes (>90% Sens/spec)

-CT better for bony margins though


Evidence

-Diagnostic block of facet joint has level 1 or level 2 on USPTF criteria

-Successful diagnostic block if >80% of pain relief post injection

-Can have false positive rate (due to local other structures)

-Though double diagnostic rarely performed


Complications

-Rare

-Case reports of infection

-Dural puncture

-Spinal anaesthesia

-Neuritis (5%)

-Transient numbness or dysaesthesias


Key anatomy to know:

-Superior articular process

-Transverse process

-Inferior articular process

-Spinous process

-Dorsal root ganglion

-Medial and lateral branch of





Procedural equipment

- Local anaesthetic

- Needles

- C-Arm




Procedural steps:

-Confirm the target level (AP view)

-Line up vertebral superior end plate of target

-Oblique the C-arm ipsilateral for Scotty Dog appearance ?Angle

-L1-L4 target is junction of SAP and TP – where nerve is midway between superior border of TP and the MAL notch (just superior to the eye of the Scotty dog)

-L5 target is dorsal ramus not MB. Goes over Ala of sacrum

-Iliac crest may block trajectory – 10deg less oblique required

-Target middle of base of SAP


Procedural steps tips:

-Caudally positioned bevel may reduce epidural spread

-0.3 ml of contrast

-0.5 ml of local anaesthetic











Outcomes

Follow up

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