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Axillary nerve injury following anterior shoulder dislocation — MSRA MCQ

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HardShoulder InjuriesAxillary nerve injury following anterior shoulder dislocationMSRA

A 38-year-old man is reviewed 6 days after reduction of a first traumatic anterior dislocation of his right shoulder. Pre- and post-reduction radiographs showed no fracture and concentric reduction. Immediately after reduction, deltoid power and sensation over the lateral upper arm were documented as normal. His pain has been improving and there is no recurrent deformity. Since yesterday, however, he has noticed numbness over the lateral aspect of the upper arm and is now unable to initiate abduction or hold the arm abducted at 90 degrees. Passive abduction is 160 degrees. External rotation is painful but preserved against resistance. Radial pulse, capillary refill, hand power and hand sensation are normal. What is the most appropriate management today?

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Correct answer: C — Make an urgent orthopaedic referral for assessment of a new axillary nerve deficit

Explanation lettering: D = shown as A · A = shown as B · E = shown as D · B = shown as E

This is a new axillary nerve deficit after shoulder dislocation. The combination of loss of sensation over the lateral upper arm (the ‘regimental badge’ area) and marked deltoid dysfunction localises to the axillary nerve. Crucially, both were normal immediately after reduction, making this a new or progressive neurological complication rather than a residual deficit documented at discharge. A normal radial pulse and intact hand neurology do not exclude an isolated axillary nerve injury. Urgent orthopaedic assessment is required because neural signs following shoulder dislocation are an urgent referral criterion. Although an acute rotator-cuff tear can also cause inability to abduct with preserved passive movement, it would not explain the new, anatomically concordant sensory loss. Ultrasound or MRI may subsequently be needed, but imaging must not delay specialist assessment of a progressive neurological deficit. A is inappropriate because rehabilitation is for uncomplicated recovery and should not be used while a new neurological deficit is unexplained. B is initially attractive because post-dislocation cuff injury is important, but it addresses the less discriminating diagnosis and delays escalation. D similarly delays assessment. E is unsafe: observation is not appropriate for newly evolving motor and sensory impairment after a dislocation.

Reference: Shoulder | DGRefHelp – NHS Dumfries and Galloway (Page crawled May 2026) — https://www.rightdecisions.scot.nhs.uk/dg-refhelp/musculoskeletal-system/shoulder/ Primary shoulder dislocation | Borders Ref Help Toolkit – NHS Borders (Reviewed 31 July 2025) — https://www.rightdecisions.scot.nhs.uk/borders-ref-help-toolkit/orthopaedic/shoulder/primary-shoulder-dislocation/ Peripheral neuropathies | Right Decisions (Page crawled May 2026) — https://www.rightdecisions.scot.nhs.uk/msk-pathways/spine-pathways/cervical-spine-pathways/supporting-information-on-relevant-conditions/peripheral-neuropathies/