Dislocated shoulder - 1
 

Important Good preparation and adequate sedation/analgesia make these easy.   
 

Background
 

The shoulder dislocates more than any other joint.
It moves almost without restriction, but pays the price of vulnerability.

The shoulder’s integrity is maintained by the glenohumeral joint capsule, the cartilaginous glenoid labrum (which extends the shallow glenoid fossa), and muscles of the rotator cuff.   
Image 

disloction background

Incidence
 

Anterior dislocations account for over 95% of dislocations, with posterior dislocations making up 4% and inferior dislocations about 0.5%.Superior and intrathoracic dislocations are extremely rare.

Sex distribution is bimodal, with peak incidence in men aged 20-30 years and women aged 61-80 years.

Shoulder dislocations occur more frequently in adolescents than childre, because the weaker epiphysel growth plates in children tend to fracture before dislocation occurs.

In older adults, collagen fibres have fewer cross links, making the joint capsule and supporting tendons and ligaments weaker and dislocation more likely. Older adults also fall more frequently. 
  
 

Things to look for in the history
Patients generally complain of severe shoulder pain and decreased range of motion with a history of trauma.
The type of trauma will tell you what sort of dislocation it is likely to be:    
 

Anterior dislocation
 

Usually result from abduction, extension, and external rotation, such as when about to punch a volleyball down over the net.

Falls onto an outstretched arm are a common cause in older adults.

The humeral head is forced out of the glenohumeral joint, rupturing or detaching the anterior capsule from its attatchment to the head of the humerus, or from its insertion to the edge of the glenoid fossa. This occurs with or without lateral detatchment.   
Image 

anterior dislocation

 
 

Posterior dislocation
 

Are caused by severe internal rotation and adduction. This is usually caused by strong unopposed contraction of the latissimus dorsi e.g. during a seizure or electrocution.

Occasionally, a severe direct blow may cause a posterior dislocation. Bilateral posterior dislocation is rare and almost always results from seizure activity.   
Image 

posterior dislocation

 

Inferior dislocation
 

Rare, but serious, inferior dislocations (luxatio erecta) may be due to axial force being applied to an arm raised overhead, such as when a motorcycle collision victim tumbles to the ground.

More commonly, the shoulder is dislocated inferiorly by indirect forces hyperabducting the arm. The neck of the humerus is levered against the acromion and the inferior capsule tears as the humeral head is forced out inferiorly.

This injury is accompanied by fracture and/or serious soft tissue injury.