Types:
Anterior dislocations: 9 times more common then posterior. Usually due to blow to anterior shoulder
Posterior dislocations: less common.
Mechanism:
Most common due to shoulder injury
May also result from direct trauma, in RTA, sports
Posterior dislocations are dangerous
Grading:
1st degree injury: incomplete tear of sternoclavicular and costoclavicular ligaments.
2nd degree injury: subluxation of clavicle from manubrial attachment due to complete breach of sternoclavicular ligament, but partial tear of costoclavicular ligament.
3rd degree injury: complete dislocation due to complete rupture of sternoclavicular and costoclavicular ligaments.
Radiograph:
Views:
1. Serendipity view - beam is tilted to 40° from vertical and directed cephalad through the manubrium of the supine patient. Normal clavicles should appear in the same horizontal plane, while anterior and posterior dislocations appear above and below the plane, respectively.
2. Hobbs view - patient sits and leans forward so that the anterior chest is in contact with the film cassette and the flexed elbows straddle the cassette and support the patient. The x-ray beam is aimed directly down through the cervical spine, projecting the sternoclavicular joints onto the film cassette.
MRI:
Articular disc injuries in 80%; Injury of anterior, posterior, interclavicular and costoclavicular ligaments in 73%, 39%, 29% and 14% of patients, respectively.
Management:
Anterior dislocations: usually managed conservatively. Closed reductions are done under anaesthesia
Posterior dislocations: more difficult and risk of injury to mediastinal strucutres. May require operative stabilization
References:
1. Benitez CL et al. Clin. Imaging. 2004 Jan-Feb; 28 (1): 59-63 (PMID: 14996451)
