Missed more often, than it is recognized…

A 50 year old man presents following a fall down some stairs. He landed on his left elbow. He complains of pain in the left shoulder. On examination, he is unable to move his L shoulder. There is swelling and pain in the region of the left shoulder. No open wound noted.

What do these Xrays of his left shoulder show, and how would you treat it?

Answer: [expand title=”Open” swaptitle=”Close”] The AP film demonstrates a classic “light bulb sign” of a posterior glenohumeral dislocation (the humeral head appears atypically rounded compared to usual). The lateral glenoid “Y” view confirms posterior dislocation of the humeral head (the humeral head is posterior to the “Y” formed by the lateral view of the scapula). An axillary view of the shoulder should be used for additional confirmation, but was not done in this case. Because the changes are subtle, posterior shoulder dislocation is often diagnosed late.

Closed reduction is considered appropriate if the dislocation is reasonably acute (within 3-6 weeks) and if any resultant defect in the humeral head is small (less than 25 % of articular surface, best judged on axillary view).

Reduction of a posterior shoulder dislocation is generally considered more difficult than reducing an anterior dislocation. Good procedural sedation will facilitate this. However, sometimes a GA in theatre will be required.

The arm will be adducted and internally rotated. Traction is applied longitudinally with the elbow in 90 degree flexion. The humeral head is disengaged from the posterior glenoid, and then the arm is externally rotated, which should reduce the dislocation, and result in a return of mobility.

The humeral head can be disengaged directly, by getting an assistant to apply pressure to the humeral head; or indirectly, by applying lateral pressure to the medial side of the upper humerus (thereby moving the humeral head laterally and increasing the adducted position of the elbow). Once the humeral head is disengaged, it should be possible to externally rotate the still adducted arm. However, the external rotation needs to be done carefully as the humeral head can fracture if it has not been disengaged from the glenoid.

Successful reduction should be signalled by a clunk and return of mobility.

A triple set of Xrays (AP, lateral and axillary) should be obtained post reduction to avoid missing any persisting dislocation. If in doubt a CT may be required. The arm requires a sling for three weeks. Orthopaedic referral is mandatory.
Natalie Vu
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