Musculocutaneous Nerve Block — FRCA Final MCQ

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HardRegional AnaesthesiaMusculocutaneous Nerve BlockFRCA Final

A 40-year-old man (ASA II, 85 kg) requires brachial plexus anaesthesia for open reduction and internal fixation of a distal humerus fracture using an upper-arm tourniquet. A conventional single-injection plexus technique is planned, without a separate injection around any terminal nerve. Which approach is best supported for reliably blocking the musculocutaneous nerve while also reducing the likelihood of tourniquet pain?

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Correct answer: C — Infraclavicular

The correct answer is C, infraclavicular. This approach deposits local anaesthetic around the brachial plexus cords, proximal to formation of the musculocutaneous nerve from the lateral cord. A systematic review found significantly fewer musculocutaneous sensory-block failures than with single-injection axillary block and less tourniquet pain than with comparator approaches. At the axilla, the musculocutaneous nerve commonly lies outside the main neurovascular sheath between coracobrachialis and biceps, so a separate targeted injection may be required. A mid-humeral technique similarly depends on multiple terminal-nerve injections. Interscalene block is designed principally for shoulder surgery and may inadequately cover lower-trunk territories. Supraclavicular block can provide effective distal-arm anaesthesia, but infraclavicular block has the stronger combination of complete cord-level coverage, musculocutaneous reliability and reduced tourniquet pain under the conditions specified.

Reference: Chin KJ et al. Infraclavicular brachial plexus block for regional anaesthesia of the lower arm, systematic review, 2013. https://pubmed.ncbi.nlm.nih.gov/23986434/