inferior shoulder dislocation

An inferior shoulder dislocation is the least common form of shoulder dislocation. The condition is also called luxatio erecta because the arm appears to be permanently held upward, in fixed abduction. The patient will often present with their hand placed on the head or near it.

Pathology

It is caused either of the following mechanisms:

  • sudden forceful arm hyperabduction
  • less commonly, direct loading force on fully abducted arm, with extended elbow and pronated forearm

The humeral head is forced against the acromion, usually with resultant inferior glenohumeral capsule rupture and rotator cuff disruption.

Radiographic features

The humeral head is displaced directly below and slightly medial to the glenoid fossa, with the arm often in marked abduction (luxatio erecta).

An inferior dislocation can mimic a subcategory of glenohumeral dislocation known as subglenoid anterior dislocation, where the humeral head rests directly inferior to the glenoid in the AP and lateral projections . It is distinguished from the latter by the humeral shaft's position parallel to the scapular spine.

MRI

MRI is performed post-reduction. Common findings include :

Complications

Inferior dislocations have a high complication rate, with secondary osseous, soft tissue. vascular, neurological, tendon, and ligament injuries.

See also