Traumatic Conditions (Dislocations): Anterior/Inferior Gleno-humeral Dislocation

Presentation

Dislocations of the shoulder joint (i.e. gleno-humeral joint), particularly anterior or anteroinferior dislocations, are common, often resulting from forced external rotation of the upper limb.

From the rear the shoulder assumes a cow’s bottom appearance clinically as the acromion becomes the most lateral aspect of the shoulder.

Fig 1: Anterior/inferior gleno-humeral dislocation	Fig 2: View of dislocation from behind with the shoulder assuming a cow’s bottom appearance

Imaging

The x-ray is typical of anterior dislocation (Fig 3). In the axial view a lesion is often seen in dislocation, known as a Hill-Sachs deformity. This always occurs in recurrent dislocations, and tells the treating physician that at least one previous dislocation has occurred.

Another lesion tends to occur as the shoulder dislocates because it tears the anterior labrum, especially in younger patients. The tear is usually to the lower part of the labrum, and this is called a Bankart lesion.

Sometimes a tear develops in the upper labrum, often referred to as a superior labral antero-posterior tear (or SLAP lesion), though this is often due to sports injuries and not dislocation. In Fig 4 the progression from the normal anatomy (left) to anterior dislocation (right) results in both these typical lesions.

Fig 3: Axial x-ray view of anterior dislocation (click on x-ray to enlarge)	Fig 4: Depicting typical lesions in a shoulder dislocation

Reduction

The sooner these injuries are diagnosed, the easier they are to reduce. This can often be achieved under entonox alone. The practice of giving synchronous opiates and benzodiazepines is not regarded as safe practice [8].

Procedural sedation should be in accordance with a locally determined and approved policy with appropriate monitoring. Intra-articular local anaesthetic has been reported to be useful [9] though when operating on a patient with an acute dislocation it is clear that the injection is often placed erroneously.

There are a variety of reduction methods in popular use, though evidence from clinical trials supporting one method over another is lacking. The Hippocratic method is safe, provided that any counter traction does not apply local force in the axilla. The Spaso Manoeuvre has gained popularity in recent years, and is a safe, easy method [10]. The classic Kocher’s Manoeuvre is successful as a method, but does carry the risk of intra-articular or spiral humeral shaft fracture.

Immobilisation

Traditionally the arm was immobilised in a sling for three weeks. Recently MR studies [11] have demonstrated that the glenoid labrum is held in the best theoretical position for healing if the arm is placed in an external rotation splint.

The management of first dislocation may influence the rate of recurrent dislocation [12]. This is based on the fact that a Bankart lesion will probably be present and if this does not heal recurrent dislocations will be inevitable.

Arthroscopy

Although figures vary it is generally accepted that below the age of 20 the risk of recurrent dislocation is as high as 90%, and the risk remains as high as 30% in those over 30 [13].

This has prompted many shoulder surgeons to adopt a policy of arthroscopy for all first dislocations, repairing the glenoid labrum in all those found to have a labral tear.