Shoulder (posterior dislocation)

Posterior dislocation (or glenohumeral dislocation) is an injury where the humeral head is forced posteriorly relative to the glenoid (1).

• less common than anterior dislocation
  • accounts for 2%–4% of all types of shoulder dislocations
  • bilateral posterior dislocations are even more rare and accounts for 5%–15% of all posterior dislocations
• usually results from an epileptic seizures, electrical shock and extreme trauma
• mechanism of injury - forced internal rotation, flexion and adduction of the shoulder
• they may become recurrent especially if the patient has generalised ligamentous laxity
• on examination, the arm is usually held in adduction, and internal rotation and patient is unable to rotate externally.

In an audit carried out on 120 posterior shoulder dislocations:

• posterior dislocations were common in men between the ages of 20-49 years
• 67% were caused by traumatic events while seizures were responsible for 31% of cases (1)

Posterior dislocations can be classified into:

• acute - if identified within three weeks of injury
• chronic – identified after three weeks of injury
  • when compared to acute dislocation, it is often less painful and have a greater range of motion (1)

Reference:

1. Jacobs RC, Meredyth NA, Michelson JD. Posterior shoulder dislocations. BMJ. 2015;350:h75.
2. Ketenci IE et al. Bilateral posterior shoulder dislocation after electrical shock: A case report. Ann Med Surg (Lond). 2015;4(4):417-21