-2 :: Topic - 5605 :: :: ::
Medical Image Database, Atlas, and Teaching File
All Topics are Peer Reviewed by an Editorial Panel

Anterior shoulder dislocation/instability:

The glenohumeral joint is the most mobile joint and hence inherently unstable. Shoulder dislocations can be either an acute event or recurrent (glenohumeral instability). Anterior glenohumeral instability is usually traumatic in nature. Anterior dislocations are most common type of shoulder dislocation (90+%) and can be secondary to direct or indirect trauma usually with arm in abduction/external rotation(ABER) position.

Shoulder stabilizers include: PASSIVE: {Glenoid fossa/Labrum, Ligaments (glenohumeral ligaments and coracohumeral ligament), Capsule, Coracoacromial arch, and Vacuum effect of GH joint}. ACTIVE: {Rotator cuff and Long head of biceps tendon}.
The inferior glenohumeral ligament complex (IGHL) is thought to be the most important stabilizer by limiting anterior/inferior GH joint subluxation and becomes taut in the ABER position.

With anterior shoulder dislocation, the ligamentous complex tears or stretches and may ultimately lead to laxity/instability. Injury of the IGHL can occur at the glenoid attachment, within the ligamentous substance, or at the humeral insertion site of the ligament. Bankart lesions represent failure of the IGHL at the glenoid attachment and may be ligamentous/labral or include bony avulsion fracture of the anterior/inferior glenoid rim (bony Bankart lesion). In addition, during an anterior shoulder dislocation the humeral head can rebound posteriorly striking the glenoid rim at its posterior/superior margin. The resulting humeral head deformity is referred to as a Hill-Sach lesion. Additional injuries occuring with an anterior dislocation include: additional fractures, other Bankart variants, capsular, loose body, rotator cuff tear, or neurovascular injury.