Anatomy Msk · Year 1 · from Anatomy Msk
Case 2: Anterior Shoulder Dislocation
Clinical Image
Source: Wikimedia Commons - Anterior Dislocation of Glenohumeral Joint - CC BY-SA 4.0
Case Presentation
A 22-year-old college football player presents to the emergency department after being tackled during a game. He was attempting to make a catch with his right arm abducted and externally rotated when another player struck his arm from behind. He reports immediate severe pain and inability to move his right shoulder. Physical examination reveals the patient holding his right arm slightly abducted and externally rotated, supported by his left hand. There is loss of the normal rounded shoulder contour with a prominent acromion and palpable humeral head anteriorly. He is unable to touch his left shoulder with his right hand (positive Dugas test). Neurovascular examination reveals diminished sensation over the lateral deltoid region (axillary nerve distribution), but distal pulses and motor function are intact. Radiographs confirm anterior dislocation with the humeral head positioned inferior and medial to the glenoid fossa. The shoulder is reduced using the Cunningham technique, and post-reduction films confirm anatomic alignment. MRI performed 2 weeks later reveals a Bankart lesion (anteroinferior labral tear). This case illustrates the inherent instability of the glenohumeral joint.
Key Learning Points
- The glenohumeral joint sacrifices stability for mobility; the glenoid fossa is shallow, covering only 25-30% of the humeral head
- The joint capsule, glenoid labrum, and rotator cuff muscles provide dynamic and static stabilization
- Anterior dislocations (95% of shoulder dislocations) typically occur with forced abduction and external rotation
- The axillary nerve is vulnerable during anterior dislocation as it wraps around the surgical neck of the humerus
- Bankart lesions (labral tears) increase risk of recurrent instability, especially in young athletes