in or out ???

the case.

A 34 year old insulin-dependent diabetic male presents to your ED following a “collapse” stating he thinks he has had a seizure. He has had hypoglycaemic seizures previously. He lost his glucometer 3 or 4 weeks ago and has been guessing his sugars and corresponding insulin doses by ‘how he feels’…

He has severe bilateral shoulder & upper thoracic pain. Any attempt to move, touch or examine either shoulder results in unbearable pain (plus a stream of four-letter expletives).

As part of his evaluation you get the following x-rays….

R Shoulder (OBL) R Shoulder (AP) CXR L Shoulder (AP) L Shoulder (OBL)

  • Bilateral humeral head/neck fractures
  • Right glenoid fracture with drumstick appearance of humeral head.
  • Left lesser tuberosity fragment.
  • Both humeral heads appear posteriorly subluxed on oblique view.

You are concerned about a bilateral posterior shoulder dislocation.

As we were unable to 100% decide whether these joints were in or out, we obtained a CT scan….

Right Shoulder:

    • Comminuted fracture of the head, anatomical and surgical necks of humerus involving both greater & lesser tuberosity.
    • Fracture through posterior aspect of the glenoid.
    • Mild posterior subluxation of articular surface of the humeral head relative to glenoid.

Left Shoulder:

    • Comminuted fracture involving the head, anatomical & surgical necks of humerus.
    • Cortical irregularity involving inferior aspect of glenoid ?non-displaced fracture.
    • Humeral head is posteriorly dislocated and wedged on the posterior aspect of glenoid.

Posterior Shoulder Dislocation

A rare event accounting for only ~2% of all glenohumeral dislocations. However, pay attention as this injury is missed in > 50% of initial presentations !!

Mechanics / Anatomy / History.

    • A distinct mechanism of action is required to cause a posterior shoulder dislocation (forceful internal rotation with adduction).
        • Lat dorsi, pec major & teres major overcome the smaller/weaker teres minor and infraspinatus.
    • Convulsive seizures or electrocution have been associated with this injury (a direct blow to the anterior shoulder or falls can also produce posterior dislocation).
    • Subdivided into subacromial, subglenoid & subspinous dislocations.
        • 98% are subacromial.


    • High index of suspicion based on mechanism.
        • Pain is not very reliable
    • Prominence of posterior shoulder w/ anterior flattening “squared off appearance”.
    • Arm held in adduction & internal rotation.
        • Inability to externally rotate.
        • Abduction is severely limited.


Standard AP images can be deceptively normal whereas the lateral/scapular Y-view is diagnostic. Abnormal features include;

    • Loss of ‘half-moon’ elliptical overlap of humeral head and glenoid.
    • “Rim sign”
        • Increased distance between anterior glenoid & articular surface of humeral head.
    • “Lightbulb” or “Drumstick” appearance of humeral head.
        • Occurs due to humeral profiling in internal rotation
    • Reverse Hill-Sachs deformity
        • Impaction fracture of anteromedial humeral head.


    • Urgent Orthopaedic consultation
    • Closed reduction may be attempted
        • Requires generous sedation & may be more appropriate for the OT.
        • Axial traction is applied in the line of the humeral shaft, with gentle pressure applied on the humeral head. External rotation may help.
    • ORIF may be required (+/- arthroplasty)
    • Post-reduction:
        • Shoulder immobilisation (minimum of 4 weeks).
        • Orthopaedic follow-up.

Complications of Posterior Should Dislocation.

    • Associated injuries include fractures to glenoid rim, greater tuberosity, lesser tuberosity & humeral head.
    • Subscapularis may be avulsed from the lesser tuberosity.
    • Neurovascular injury is rare (generally protected due to its anterior location).
    • 30% of patients have recurrent posterior dislocation.
    • Degenerative joint disease.

Firstly, here are the 3D reconstructions from his CT.

Left Shoulder 3D Left Shoulder 3D1 Right Shoulder 3D

This patients’ injury had actually occurred the night before his presentation (some 14-15 hours earlier). Taking this into consideration, and given his associated humeral fractures it was decided that the relocation attempt should take place in the OT with a general anaesthetic and full muscle relaxation.

Despite multiple attempts/techniques his shoulder could not be relocated.

He returned to theatre 48 hours later for an open-reduction and internal fixation.

  1. Rosenʼs Emergency Medicine. Concepts and Clinical Approach. 7th Edition
  2. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide. 7th Edition.


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