Inferior Shoulder Dislocation: Clinical Features, Imaging, Treatment & Complications

Inferior shoulder dislocation is Complete inferior displacement of the humeral head out of the glenoid
Inferior shoulder dislocation is rare, accounting for less than 1% of all shoulder dislocations

Mechanism of injury

Severe abducting force on the humerus causing hyperabduction
humerus will act as a lever and the acromion act as a fulcrum
humeral head is lifted across the glenoid socket and inferior dislocation occurs
humeral head stay in the sub glenoid position with the humeral shaft pointing upwards (luxation erecta)
Sometimes the arm drops spontaneously after the head of the humerus is slipped to a sub coracoid position leading to anterior shoulder dislocation instead of inferior

Patient present with arm is locked in abduction and forward elevation and they will be in severe pain
Patient can not adduct their arm
The head of humerus is felt in or below the axilla
Always examine for neurovascular damage (high risk)
Look for other injuries in other parts of the body

On AP shoulder x ray:
- the humeral head is sitting below the glenoid
- humeral shaft is in abducted position
- Look for associated fractures of the glenoid or proximal humerus to distinguish between simple dislocation (with/without tuberosity fracture) from a fracture dislocation

Closed reduction is indicated for simple inferior shoulder dislocations mostly under sedation and sometimes under GA
In closed reduction, patients placed supine and then:
- Pulling upward in the line of the abducted arm
- At the same time, an assistant will put a sheet around the patient’s chest providing countertraction downward
- Reexamination for neurovascular injuries after reduction
The arm is rested in a sling until pain subsides
Active movements of the elbow, wrist and hand should be started after reduction of the shoulder
Active movements of the shoulder are done after pain subsides and abduction is avoided for 3 weeks

Open reduction indications
- Irreducible inferior shoulder dislocation: If the humeral head is stuck in the soft tissues
- In case of Fracture dislocations
Arthroscopic or open repair to capsulolabral structures, and rotator cuff tears after the reduction is indicated to active younger patients

Postural downward displacement of the humerus due to weakness and laxity of the muscles around the shoulder
This occur after trauma and shoulder splintage and here the shaft of the humerus lies in the normal anatomical position at the side of the chest.
This condition is harmless and resolves as muscle tone is regained and must be differentiated from inferior shoulder dislocation