Have you ever been working a shift at 3 am and wondered, “Am I missing something? I’ll just splint and instruct the patient to follow up with their primary doctor in 1 week.” This is a reasonable approach, especially if you’re concerned there could be a fracture. But we can do better. Enter the “Can’t Miss” series: a series organized by body part that will help identify injuries that ideally should not be missed. This list is not meant to be a comprehensive review of each body part, but rather aims to highlight and improve your sensitivity for these potentially catastrophic injuries. Now: the shoulder
Third most common musculoskeletal complaint, only to low back pain and neck pain .
Epidemiology: Posterior dislocations are much less common than anterior, but associated with more life-threatening injuries such as pneumothorax and laceration of great vessels, trachea, or esophagus . May see pneumothorax with anterior dislocation.
Mechanism: Usually high speed motor vehicle collision or contact sports injuries
Symptoms: Severe pain exacerbated by arm motion and lying supine 
Physical Exam: Medial clavicle end is less visible and often not palpable. The patient may have signs of impingement of important mediastinal structures, for example stridor or shortness of breath.
Diagnostic Imaging: Routine clavicle radiographs or “serendipity” views may not be diagnostic. If there is a high index of suspicion, the patient needs a CT chest with contrast to view the underlying vessels.
Anterior dislocations may be discharged without reduction attempt if uncomplicated .
Posterior dislocations require orthopedics consultation for closed reduction of posterior dislocations . Because of the close-lying great vessels, these reductions should be performed at a facility that has vascular surgery on call.
Figure 1: Right posterior sternoclavicular dislocation. Case courtesy of Dr Brendon Friesen, Radiopaedia.org.
Epidemiology: Acromioclavicular joint injuries account for half of all shoulder injuries among those involved in contact sports .
Mechanism: Direct trauma to acromioclavicular joint, typically a fall on a adducted arm
Symptoms: Distal clavicle or shoulder pain
Physical Exam: Tenderness over acromioclavicular joint
Diagnostic X-Ray: Grade 1 AC injuries are characterized by pain at the AC joint with a negative film. On the other hand, Grade 4 injuries often require lateral view for diagnosis, as the clavicle is dislocated posteriorly. Check out our SplintER series post on acromioclavicular separations for more information.
Treatment: Rest, ice, immobilization with sling followed by early range of motion exercises at 7-14 days
Figure 2: Various Acromioclavicular joint injuries. Case courtesy of Andrew Murphy, Radiopaedia.org.
Scapular body: Rare but associated with many significant injuries
Acromion fractures: Rare but often associated with other injuries
Scapular neck fractures: 25% of all scapular fractures 
Glenoid fractures: 50% of all scapular fractures 
Mechanism: Scapular body and acromion fractures generally require significant force and usually occur from blunt trauma. Scapular neck and glenoid fractures usually occur from lower mechanisms, such as falling on an outstretched arm, falling onto the elbow, or a lateral blow to the shoulder .
Symptoms: Posterior shoulder or scapular pain, may have pain elsewhere if concomitant injury
Physical Exam: Tender to palpation over scapula or posterior thoracic cage
Diagnostic X-Ray: If a scapular fracture is seen on x-ray, should strongly consider CT to assess for concomitant injuries
Treatment: Non-displaced fractures of the body, neck and glenoid require sling and outpatient follow up . Patients with acromion fractures should be treated with shoulder immobilizer .
Many of the common pathology outlined above can cause concomitant injuries. Be sure to check for pneumothoraces and rib fractures when visible on the obtained films, and the dreaded incidental finding of the Pancoast Tumor, Osteonecrosis of humeral head (Hass Disease). If the patient reports no trauma, or minimal trauma that does not explain their level of pain or disability, consider septic joints.