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Shoulder dislocation and glenohumeral instability
Most shoulder dislocations are anterior, from abduction and external rotation; the axillary nerve is checked before and after reduction, and the risk of recurrence is very high in young people, so early surgical repair is considered in young athletes.
Why it matters in the exam
The typical stem describes a young person who fell on an abducted, externally rotated arm, with a squared-off shoulder, a humeral head felt at the front and the arm supported by the other hand. Anterior dislocation makes up the great majority of shoulder dislocations. The nerve most often injured is the axillary nerve, so sensation over the lateral arm (the regimental badge area) and deltoid power are checked before and after reduction and documented. A radiograph before reduction excludes an associated fracture, and one afterwards confirms success. The dislocation causes two typical lesions: a tear of the anteroinferior labrum (Bankart) and an impaction defect in the posterolateral humeral head (Hill-Sachs). The risk of recurrence depends mainly on age: it is very high in teenagers and young athletes and falls sharply after age 40, so a young contact athlete may benefit from repair after the first dislocation. In adults older than 40 the important complication is rather a rotator cuff tear. Posterior dislocation is less common, occurs in seizures or electric shock, and the arm is fixed in internal rotation with no external rotation; it is often missed on an AP radiograph alone, so an axillary view or CT is needed. When there is significant glenoid bone loss, soft tissue repair alone fails, and a bone transfer operation (Latarjet) is needed. After reduction a sling is given briefly for comfort, and physiotherapy begins to strengthen the stabilising muscles.
Key points
- Most dislocations are anterior: abduction and external rotation.
- Check and document the axillary nerve before and after reduction.
- Bankart in the labrum and Hill-Sachs in the humeral head.
- Recurrence is very common in young people; above age 40 — think of a cuff tear.
- Posterior dislocation in seizures or electric shock; an axillary view is needed.
Summary table
| Feature | Anterior dislocation | Posterior dislocation |
|---|---|---|
| Frequency | The great majority of dislocations | Relatively rare |
| Mechanism | Abduction and external rotation, fall on an abducted arm | Seizure, electric shock, direct blow from the front |
| Clinical appearance | Squared-off shoulder, head felt in front | Arm fixed in internal rotation, cannot rotate outward |
| Imaging | AP and lateral radiographs before and after reduction | AP view may look almost normal; axillary view or CT |
| Associated injuries | Bankart, Hill-Sachs, axillary nerve; above age 40 — cuff tear | Reverse Hill-Sachs, posterior glenoid fracture |
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Sources
- Rockwood and Green's Fractures in Adults, 9th ed. (2019) — Glenohumeral Instability
- Rockwood and Matsen's The Shoulder, 5th ed. (2017) — Glenohumeral Instability
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.