Shoulder Dislocation
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Direct answer
The shoulder is the most frequently dislocated joint in the body, and the vast majority displace anteriorly during abduction and external rotation. The limb is held slightly abducted and externally rotated, the squared shoulder loses its contour, and the axillary nerve must be tested — regimental badge sensation and deltoid contraction — before and after every reduction. After analgesia or sedation, closed reduction by the Kocher or traction-countertraction method is followed by radiography, neurovascular re-examination and a period of immobilisation, since recurrence is common in the young.
What you must remember
- Anterior dislocation dominates: the humeral head comes off the glenoid anteriorly during abduction-external rotation to lie under the coracoid; the arm is held in slight abduction and external rotation.
- The two lesions to name: the Bankart lesion — tear of the anteroinferior labrum (or a bony Bankart avulsion of the glenoid rim) — and the Hill-Sachs lesion, an impaction defect on the posterolateral humeral head.
- Test the axillary nerve every time: numbness over the regimental badge patch and weak deltoid contraction before and after reduction; the musculocutaneous and suprascapular nerves are less frequently involved.
- Reduction methods: Kocher's — traction, external rotation, adduction, then internal rotation — or traction-countertraction, always with adequate analgesia or sedation and muscle relaxation.
- Post-reduction protocol: confirm congruence on film, recheck neurovascular status and immobilise in a sling; arthroscopic Bankart repair is offered to young athletes, in whom recurrence is highest.
- Posterior dislocation follows seizures, electrocution or a direct anterior blow — the arm is locked in internal rotation with blocked external rotation, and the AP film may look falsely normal; the light-bulb sign and reverse Hill-Sachs lesion are the clues.
- Elderly dislocators are likelier to have an associated greater tuberosity fracture or rotator cuff tear than recurrent instability.
Common confusion
Anterior versus posterior is decided by the posture of the arm, and posterior dislocations are the famously missed ones: after a seizure, an arm that will not rotate outward with a normal-looking AP film is posterior until a lateral or axillary view proves otherwise. The lesions are then conflated: the Bankart is on the glenoid side, the Hill-Sachs on the humeral head — both stamps of anterior instability that justify surgery in the recurrent dislocator. And the numb patch after reduction is usually a recovering axillary neuropraxia, but it must be documented before reduction.
Exam-focused takeaway
NEET-PG builds its stems on mechanism and posture: a fall with the arm flung up and out with a squared shoulder diagnoses anterior dislocation. Sequenced questions ask for the nerve tested (axillary, regimental badge) and the method (Kocher's) before X-ray confirmation, and lesion-matching one-liners pair Hill-Sachs and Bankart with anterior instability. Seizure-related internal-rotation locking points to posterior dislocation and its light-bulb sign, while elderly stems add greater tuberosity fracture and rotator cuff tear, and young athletes are selected for stabilisation.
Frequently asked questions
Which is the commonest type of shoulder dislocation?
Anterior dislocation, produced by abduction and external rotation, with the head displaced anteroinferiorly below the coracoid.
Which nerve is tested in shoulder dislocation?
The axillary nerve — sensation over the regimental badge area and deltoid power — before and after reduction.
What are the Bankart and Hill-Sachs lesions?
A Bankart lesion is a tear of the anteroinferior glenoid labrum, while a Hill-Sachs lesion is a posterolateral impaction defect of the humeral head; both follow anterior dislocation.
How is an anterior shoulder dislocation reduced?
With analgesia or sedation, by the Kocher technique of traction, external rotation, adduction and internal rotation, or by traction-countertraction.
Why is posterior dislocation often missed?
The arm is held internally rotated after a seizure and the AP radiograph can look deceptively normal, so a lateral or axillary view is needed to confirm it.