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  Young man involved in a high-speed motorcycle collision with diminished left upper extremity pulses What are the pertinent imaging findings? What is your leading diagnosis? How do you explain the clinical findings? (Click for a larger image.) Case Details Radiologic Findings - AP portable trauma bay chest radiograph (Fig. 1A) with accompanying edge-enhanced image (Fig. 1B) demonstrates a widened mediastinum with poor definition of the transverse aorta, aorticopulmonary window and right tracheobronchial angle consistent with hemomediastinum in this setting. Left perihilar and upper lobe air space disease is  present consistent with a pulmonary contusion. The left diaphragm and left heart border is crisp reflective of an ipsilateral pneumothorax. Note the significant left chest wall trauma characterized by acute fractures of the 1st through 8th ribs; comminuted scapular fracture; displaced left mid-shaft clavicular fracture; and the marked separation of the left scapula from the chest wall. The scapulothoracic ratio (i.e., thoracic spinous process-medial scapular  border distance) is 1.8. Selected contrast-enhanced chest CT axial (Fig. 2A-2D) (mediastinal windows); coronal (Fig. 3A-3C) (bone windows); and 3-D volume rendered images (Fig. 4A-C) demonstrate these injuries to better advantage. Compare the relationship of the left and right scapula to the thoracic cage on the 3-D images (Fig. 4A-4C). Answer Diagnosis: Left Scapulothoracic dissociation  Differential Diagnosis   None Discussion   Scapulothoracic dissociation  is a rare but serious devastating closed forequarter amputation of the upper extremity resulting from a direct blow to or severe traction on the shoulder girdle. 50-60% of patients with scapulothoracic dissociation are motorcyclists. The postulated mechanism of injury involves attempting to hold onto the handlebars while being forcibly thrown. Injuries to all-terrain vehicle riders occur in a similar manner and are becoming more common. Clinically, there is near complete disruption of the forequarter from the torso. Clinical Findings  Massive soft-tissue swelling, and partial or complete tears of the deltoid, pectoralis minor, rhomboids, levator scapulae, trapezius, and latissimus dorsi muscles are usually present. Concomitant injury to the ipsilateral brachial plexus, subclavian artery and or subclavian vein invariably occurs. The axillary artery is not infrequently injured. The neurological deficit is most often the result of complete avulsion of the brachial plexus but incomplete neurapraxia is possible. There is also a high prevalence of other often severe thoracic and chest wall injuries. Imaging Findings   Chest Radiography      Radiographic hallmark: lateral displacement of the scapula o   Scapulothoracic ratio (abnormal:normal, ≥ 1.40 on a well -centered frontal exam) (i.e., thoracic spinous process-medial scapular border distance) o   Concomitant fracture of ipsilateral clavicle with lateral displacement of distal fragment, acrominoclavicular separation, and sternoclavicular fracture MDCT / MRI      Depicts conventional radiographic findings to better advantage    Separation of the scapula from the chest wall    An excessively large hematoma may be suggestive of a serious vascular injury    Chest wall or paraspinous hematoma may be identified    Pseudomeningocele; indicative of spinal root avulsion    MRI offers more detailed information regarding brachial plexus injury Treatment      Urgent surgical exploration mandatory for patients with active hemorrhage, expanding hematoma, or severe hand ischemia    Complete disruption of brachial plexus; primary amputation should be considered    Partial brachial plexus injury; some potential for functional recovery o   Direct repair of nerve injuries may be considered if patient is stable o   Urgent revascularization of the ischemic upper extremity  Prognosis      Early recognition and aggressive treatment crucial; outcome is not dependent on management of the arterial injury, but rather on the severity of the neurological deficit    Severe long-term disability may result from ischemia and brachial plexus damage    Complications may ultimately require shoulder arthrodesis and amputation Selected Readings  1.   Lee GK, Suh KJ, Choi JA, Oh HY. A Case of Scapulothoracic Dissociation with Brachial Plexus Injury: Magnetic Resonance Imaging Findings.  Acta Radiol   2007; 48(9): 1020-1023. 2.   Witz M, Korzets Z, Lehmann J. Traumatic Scapulothoracic Dissociation.  J Cardiovasc Surg (Torino)  2000; 41(6): 927-929. (Click for a larger image.)   
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