Learning Radiology xray montage

Luxatio Erecta
Inferior Shoulder Dislocation

Types of dislocations about the shoulder

  • Glenohumeral dislocation (the most common by far)
  • Acromioclavicular dislocation (12%)
  • Sternoclavicular dislocation (uncommon)

Types of glenohumeral dislocations

  • Inferior shoulder dislocation (1-2%)
    • Luxatio erecta ─ uncommon form of shoulder dislocation
      • Extremity held over head in fixed position with elbow flexed
    • Mechanism
      • Severe hyperabduction of arm resulting in impingement of humeral head against acromion
      • Humeral articular surface faces inferiorly
    • Complications
      • Rotator cuff tear
      • Fracture of acromion with or without inferior glenoid fossa and with or without fracture of the greater tuberosity
      • Neurovascular injury
  • Anterior or subcoracoid shoulder dislocation (most common) (96%)
    • Mechanism
      • External rotation and abduction
      • 40% recurrent
    • Age
      • Younger individuals
    • May be associated with:
      • Fracture of greater tuberosity (15%)
      • Bankart lesion
        • Fracture of anterior glenoid rim
      • Hill-Sachs defect (50%)
        • Impaction fracture of posterolateral surface of humeral head due to impaction of humeral head against anterior rim of glenoid during dislocation
  • Posterior shoulder dislocation (2nd most common) (2-4%)
    • Causes
      • Traumatic
        • Convulsive disorders or electroshock therapy
      • Nontraumatic
        • Congenital or developmental
        • May be done voluntarily, especially in children
      • Usually due to axial loading of an adducted and internally rotated arm
    • In >50% unrecognized initially and subsequently misdiagnosed as frozen shoulder
      • May be difficult to see on AP radiograph
      • Typically, a scapular Y view or transthoracic lateral of the humeral head demonstrate a posterior dislocation better
    • Imaging signs of posterior dislocation
      • Rim sign (66%) = distance between medial border of humeral head and anterior glenoid rim <6 mm
      • Humeral head is fixed in internal rotation no matter how forearm is turned – “lightbulb sign”
      • May be associated with:
        • Trough sign (75%) = "reverse Hill-Sachs" = compression fracture of anteromedial humeral head
        • Fracture of posterior glenoid rim
        • Avulsion fracture of lesser tuberosity
          • Isolated  fractures of the lesser tuberosity should raise suspicion of an associated posterior dislocation
  • Superior shoulder dislocation (least common) (<1%)
    • Humeral head driven upward through rotator cuff
    • May be associated with fracture of humerus, clavicle or acromion


Luxatio Erecta (Inferior Dislocation). The humeral head (white arrow) lies below (inferior) to the glenoid (black arrow) and the arm is fixed in abduction.
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