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Glenohumeral Instability

Glenohumeral Instability


A dislocation is the loss of contact between the bone areas of a joint. Glenohumeral dislocation (dislocated shoulder) is the most frequent dislocation (approximately 50% of all dislocations). The discrepancy between the size and the shape of the glenoid fossa (which resembles a golf ball) gives the joint a large amount of mobility yet also makes it highly vulnerable to dislocation. The capsule, the ligaments and the labrum are there to prevent this from occurring.

In 95% of dislocated shoulders, the humerus is displaced anteriorly and of these, most (between 50-70%) occur in patients under 30 and mostly males are affected. In clinical terms, the patient with a dislocated shoulder resists the least attempt of passive mobility and the active adduction of the arm, presenting asymmetry and deformity in the shoulder: the acromion protrudes and the humeral head may be palpable anteriorly, in the event of a dislocation.

Glenohumeral instability is a frequent cause of pain and especially of functional limitation of the shoulder. This brings about a loss of connection between the humeral head and the glenoid fossa in the joint.

There are different injuries related to previous dislocations such as tears in connecting elements (ligaments, capsule and especially the labrum), fractures, rotator cuff tears, etc.


When there are episodes of repeated shoulder dislocations, these lead to chronic instability that is known as Recurrent Shoulder Dislocation.

There are different causes for this pathology. The trauma instances which lead to injuries to the glenoid labrum, the capsule or the ligaments may cause unidirectional instability. In hyper-mobile (either hereditary or acquired) patients, mobility is greater than average and the instability tends to be multi-directional.


Acute dislocation: pain, functional loss of strength and shoulder deformity.

Recurrent dislocation: repeated instances of dislocation or subluxation and with a sensation of reluctance to make "dislocating actions" (throwing movements).


Multi-directional instability is usually treated with physiotherapy and muscle strengthening exercises.

In the event that instability should be recurring, especially trauma instabilities, surgery is often required and although many different types have been documented the types of surgery could be summarised as:

  • "repairing" the torn structures for instance using anchors to repair the labrum.
  • "tightening" the loose structures such as the joint capsule.
  • "reinforcing" with artificial ligaments or "bone caps" in other cases.

In all of the aforementioned cases application of platelet-rich plasma helps the different structures affected, repaired or reinforced during surgery to heal.