Mr O’Laughlin is from Lehigh University, Bethlehem, Pennsylvania; and Drs Varich and Bancroft are from the Department of Radiology, Florida Hospital, Orlando, Florida.
Mr O’Laughlin and Dr Varich have no relevant financial relationships to disclose. Dr Bancroft receives book royalties from Lippincott and is a speaker for IICME.
Correspondence should be addressed to: Laura W. Bancroft, MD, Department of Radiology, Florida Hospital, 600 E Rollins, Orlando, FL 32803 (email@example.com).
A 13-year-old boy presented to the emergency department with chest pain after sustaining an injury to the chest when a football player’s helmet “speared” him.
For answer see page 554
Posterior Sternoclavicular Dislocation
Answer to Radiologic Case Study
Case facts appear on page 498
Aposterior sternoclavicular dislocation occurs when the medial end of the clavicle loses its proper articulation with the sternum and is displaced posteriorly. Sternoclavicular dislocations are uncommon among all shoulder dislocations, accounting for only 2% to 3% of all cases.1
Classically, anterior sternoclavicular dislocation is seen much more frequently, with a 20:1 ratio.2 This is, in part, due to a greater strength of the posterior sternoclavicular ligament compared with the anterior ligament. Four strong ligaments (intra-articular disk and costoclavicular, interclavicular, and capsular ligaments) anchor the clavicle to the sternum in a saddle-type joint that allows for both articulation and stability of the clavicle. A posterior sternoclavicular dislocation requires all 4 of these ligaments to be torn, which is another reason that it is less frequent than anterior dislocations.3
Although rare, a posterior sternoclavicular dislocation is considered a medical emergency and requires immediate attention due to the vital structures and organs that lie immediately posterior to the joint. The innominate artery and vein lie posterior to the right sternoclavicular joint, and the trachea and esophagus lie posteromedially. On the left side, the common carotid artery and left subclavian vein are located directly posterior to the sternoclavicular joint. Compression or damage to the great vessels, trachea, esophagus, or lungs that arise from sternoclavicular dislocations could result in significant morbidity and mortality, if not properly managed.3,4
Dislocation of the sternoclavicular joint involves tearing of the 4 main ligaments and displacement of the clavicle behind the manubrium. This is often implemented by acute trauma. The main mechanism that contributes to the dislocation involves a direct anteroposterior (AP) force applied to the medial aspect of the clavicle. A secondary mechanism that may cause a posterior sternoclavicular dislocation requires a great amount of direct or indirect force applied posterolaterally to the shoulder and arm.4
Patients typically present to the emergency department with shoulder pain, chest pain, and possible complaints of dyspnea, dysphagia, or dysphonia. Patients with posterior sternoclavicular dislocations sometimes tilt their head unknowingly toward the side of dislocation in an attempt to lessen the pain.5,6 Localized soft tissue swelling is also common, accompanied by a marked decreased range of motion in the shoulder.7 On questioning, patients will report a history of trauma resulting in a significant impact on the chest. Posterior sternoclavicular dislocations are most commonly the result of a sports injury or motor vehicle accident.4,6
A complete and accurate evaluation of a sternoclavicular dislocation is necessary to determine its treatment method.5 Standard chest radiographs are often ordered for patients presenting with acute chest pain. However, the presence of a posterior sternoclavicular dislocation may not always be detected on AP views if there is no associated superior or inferior displacement of the clavicular head or if the sternoclavicular articulation is obscured by the superimposed ribs or mediastinal structures (Figure 1).2,5 Asymmetry of the 2 clavicles and manubrium usually indicates a sternoclavicular dislocation, although this may not be well visualized in subtle…