Facet Joint Medial Branch Innervation — FRCA Final MCQ

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ModeratePain MedicineFacet Joint Medial Branch InnervationFRCA Final

A 60-year-old man (ASA III) with chronic pain has been referred for a lumbar medial branch block as a diagnostic test before considering radiofrequency denervation for facet joint-mediated low back pain. How many medial branch nerves need to be blocked to denervate a single facet joint?

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Correct answer: C — 2

Each lumbar facet (zygapophyseal) joint receives dual innervation from the medial branch of the posterior ramus at the same level AND the level above. Therefore, to denervate a single facet joint, two medial branch nerves must be blocked. For example, the L4/5 facet joint is innervated by the L3 and L4 medial branches. This is important for diagnostic blocks (which must be concordant to predict success of radiofrequency denervation) and for the RF procedure itself.

Reference: Faculty of Pain Medicine – 2021 – Interventional pain procedures; NICE – 2024 – NG59 Low back pain