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Luxatio Erecta (Inferior Dislocation of the Shoulder)

 

         Types of dislocations about the shoulder

o       Glenohumeral dislocation (the most common by far)

o       Acromioclavicular dislocation (12%)

o       Sternoclavicular dislocation (uncommon)

         Types of glenohumeral dislocations

o       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

 


Luxatio Erecta.
Humeral head (blue arrows) faces inferiorly and is located below the rim of the
glenoid (red arrow) in this uncommon inferior dislocation of the shoulder in which the
arm is fixed in an upright position usually with the elbow flexed.

For a larger photo of the same image without arrows, click here

 

         Complications

         Rotator cuff tear

         Fracture of acromion with or without inferior glenoid fossa and with or without fracture of the greater tuberosity

         Neurovascular injury

o       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

o       Fracture of anterior glenoid rim

         Hill-Sachs defect (50%)

o       Impaction fracture of posterolateral surface of humeral head due to impaction of humeral head against anterior rim of glenoid during dislocation

o       Posterior shoulder dislocation (2nd most common) (2-4%)

         Causes

         Traumatic

o       Convulsive disorders or electroshock therapy

         Nontraumatic

o       Congenital or developmental

o       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:

o       Trough sign (75%) = "reverse Hill-Sachs" = compression fracture of anteromedial humeral head

o       Fracture of posterior glenoid rim

o       Avulsion fracture of lesser tuberosity

         Isolated  fractures of the lesser tuberosity should raise suspicion of an associated posterior dislocation

o       Superior shoulder dislocation (least common) (<1%)

         Humeral head driven upward through rotator cuff

         May be associated with fracture of humerus, clavicle or acromion

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Dahnert 5th Edition