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Posterior shoulder dislocation after seizure — MSRA MCQ

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HardShoulder InjuriesPosterior shoulder dislocation after seizureMSRA

A 46-year-old man is seen in general practice the morning after a witnessed generalised tonic-clonic seizure. Since regaining consciousness, he has had severe left shoulder pain and has kept the arm adducted and internally rotated. There was no fall or direct trauma. He cannot actively abduct the arm and passive external rotation is blocked at neutral. The shoulder contour is subtly flattened anteriorly but there is no obvious deformity. Distal pulses, hand sensation and deltoid sensation are normal. An anteroposterior shoulder radiograph obtained overnight at an urgent treatment centre was reported as showing no fracture. What is the most appropriate next step?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: E — Refer to the emergency department today for assessment of a possible unreduced posterior dislocation, including orthogonal shoulder imaging

Explanation lettering: C = shown as B · B = shown as C

This presentation should be treated as a possible unreduced posterior glenohumeral dislocation. A generalised tonic-clonic seizure is a classic mechanism, and the fixed internally rotated posture with marked passive loss of external rotation is particularly discriminatory. Posterior dislocations may have only subtle contour changes and are frequently missed on anteroposterior radiographs; an axillary, modified axillary/Velpeau, or other orthogonal view is needed to establish glenohumeral alignment. An unreduced traumatic shoulder dislocation requires emergency assessment rather than community investigation or conservative treatment. A is plausible because acute cuff tears can cause profound weakness after an acute shoulder event, but they do not usually produce a mechanical block to passive external rotation and should not distract from suspected dislocation. B is inappropriate because physiotherapy must not precede exclusion of an unreduced dislocation. C risks masking symptoms and delaying diagnosis of a structural emergency. D is unsafe: the relevant issue is inadequate imaging projection, not the timing of a further anteroposterior film. Normal distal neurovascular findings do not exclude dislocation.

Reference: Upper limb | Borders Ref Help Toolkit (2025) — https://www.rightdecisions.scot.nhs.uk/borders-ref-help-toolkit/physiotherapy/msk-physiotherapy/upper-limb/ Bilateral posterior shoulder dislocation: the importance of the axillary radiographic view (2001) — https://pubmed.ncbi.nlm.nih.gov/11436917/ Neglected posterior dislocation of the shoulder: A systematic literature review (2015) — https://pubmed.ncbi.nlm.nih.gov/30035045/