In a shoulder dislocation, there is separation of the humerus from the glenoid of the scapula at the glenohumeral joint. The shoulder is exceptionally manoeuvrable and sacrifices stability to enable an increase in function. Therefore, it is vulnerable to dislocation, and is the most commonly dislocated large joint. In fact approximately half of major joint dislocations seen in emergency departments are of the shoulder 1.
This article contains a general discussion on shoulder dislocation. For specific dislocation types please refer to the following articles:
anterior shoulder dislocation
posterior shoulder dislocation
inferior shoulder dislocation
Types
Shoulder dislocations are usually divided according to the direction in which the humeral exits the joint:
anterior > 95%
posterior 2-4% 2
inferior (luxatio erecta) < 1%
In addition it is useful to also include a description of their time course:
Radiographic features
Plain film
X-rays (AP and lateral +/- axillary view) are sufficient in almost all cases to make the diagnosis, although CT and MR are often required to assess for the presence of subtle fractures of the glenoid rim or ligamentous / tendinous injuries respectively.
Anterior and inferior dislocations are usually simple diagnoses, with the humeral head and outline of the glenoid being incongruent.
Posterior dislocations can be difficult to identify on an AP view only (as may be obtained in the setting of secondary survey of a trauma) as the humeral head moves directly posteriorly and congruency may appear to be maintained (at least at first glance).
All dislocations should be easily identified on trans-scapular Y views. In an enlocated (normally aligned) joint, the humeral head will project centred over the centre of the Y formed by the coracoid, blade of the scapula and spine of the scapula.
Report checklist
In addition to reporting the presence of a dislocation a number of features and associated findings should be sought and commented upon:
direction of dislocation
associated fractures/injuries
Hill-Sachs lesion
bony Bankart lesion
proximal humeral fractures
clavicular fracture
acromioclavicular joint disruption
acromial fracture
It is also important to remember to scrutinise the ribs and portion of the lungs and mediastinum included in the film for unexpected findings. Think about the soft tissue structures that might be injured, particularly the neurovascular bundle with inferior dislocations.
Differential Diagnosis
shoulder pseudo subluxation: apparent inferior displacement of the humeral head from capsular distension secondary to a haemarthrosis or large effusion
This article contains a general discussion on shoulder dislocation. For specific dislocation types please refer to the following articles:
anterior shoulder dislocation
posterior shoulder dislocation
inferior shoulder dislocation
Types
Shoulder dislocations are usually divided according to the direction in which the humeral exits the joint:
anterior > 95%
posterior 2-4% 2
inferior (luxatio erecta) < 1%
In addition it is useful to also include a description of their time course:
- acute
- chronic
- recurrent
Radiographic features
Plain film
X-rays (AP and lateral +/- axillary view) are sufficient in almost all cases to make the diagnosis, although CT and MR are often required to assess for the presence of subtle fractures of the glenoid rim or ligamentous / tendinous injuries respectively.
Anterior and inferior dislocations are usually simple diagnoses, with the humeral head and outline of the glenoid being incongruent.
Posterior dislocations can be difficult to identify on an AP view only (as may be obtained in the setting of secondary survey of a trauma) as the humeral head moves directly posteriorly and congruency may appear to be maintained (at least at first glance).
All dislocations should be easily identified on trans-scapular Y views. In an enlocated (normally aligned) joint, the humeral head will project centred over the centre of the Y formed by the coracoid, blade of the scapula and spine of the scapula.
Report checklist
In addition to reporting the presence of a dislocation a number of features and associated findings should be sought and commented upon:
direction of dislocation
associated fractures/injuries
Hill-Sachs lesion
bony Bankart lesion
proximal humeral fractures
clavicular fracture
acromioclavicular joint disruption
acromial fracture
It is also important to remember to scrutinise the ribs and portion of the lungs and mediastinum included in the film for unexpected findings. Think about the soft tissue structures that might be injured, particularly the neurovascular bundle with inferior dislocations.
Differential Diagnosis
shoulder pseudo subluxation: apparent inferior displacement of the humeral head from capsular distension secondary to a haemarthrosis or large effusion
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