What is the differential diagnosis for a shoulder injury sustained during a car crash?

Differential Diagnosis for Shoulder Injury During Car Crash

The differential diagnosis for traumatic shoulder injury from a motor vehicle crash includes clavicle fractures, proximal humerus fractures, scapular fractures, acromioclavicular (AC) joint injuries, glenohumeral dislocations, rotator cuff tears, and labral/labroligamentous complex injuries. 1, 2

Bony Injuries

Clavicle Fractures

• Clavicle fractures are among the most common traumatic shoulder injuries, particularly affecting young adults and males following direct trauma 1, 2, 3
• More than 80% can be managed conservatively 3
• Middle third fractures in active individuals may warrant surgical consideration 4

Proximal Humerus Fractures

• Less common than clavicle fractures, typically occurring in elderly patients 3
• Approximately 85% can be managed nonoperatively 3
• Displaced or unstable fractures require surgical intervention 4

Scapular Fractures

• Scapular fractures occur with high-energy blunt trauma and have different mechanisms than other shoulder injuries in motor vehicle crashes 2, 5
• Occupants with scapular fractures are 3 times more likely to be male and tend to be taller and heavier 5
• Should be considered distinct from other shoulder injuries in crash scenarios 5

Joint Injuries

Acromioclavicular (AC) Joint Injuries

• AC dislocations are frequently misclassified on anteroposterior views alone—axillary or scapula-Y views are absolutely essential 1, 2, 6
• Graded as types I through VI 3, 4
• Types I and II: conservative management 3
• Types IV, V, and VI: surgical indication 3, 4
• Type III: controversial—surgery considered for active individuals 3, 4

Glenohumeral Dislocations

• 80% are anterior dislocations 3
• Can be missed on AP views alone, requiring axillary or scapula-Y views for accurate diagnosis 1, 2
• First-time dislocation in young athletes may warrant surgical consideration 4

Sternoclavicular Dislocations

• Posterior sternoclavicular dislocations require urgent surgical referral due to risk of vascular compromise 4

Soft Tissue Injuries

Rotator Cuff Tears

• Acute traumatic rotator cuff tears are frequently underreported because patients may not seek immediate treatment 2
• Most can initially undergo conservative management 1, 2, 4
• Traumatic massive rotator cuff tears may require expedited surgical repair to achieve optimal functional outcomes 1
• Full-thickness tears in appropriate candidates warrant surgical consideration 4

Labral and Labroligamentous Complex Injuries

• Include Bankart lesions and superior labral anterior-to-posterior (SLAP) tears 1, 2
• Occur with traumatic dislocations or direct trauma 2
• Labral tears without instability can be managed conservatively 2

Critical Diagnostic Approach

Initial Imaging Protocol

• Obtain upright radiographs with minimum three views: AP in internal rotation, AP in external rotation, and axillary or scapula-Y view 1, 2, 6
• Upright positioning is essential because supine radiographs underrepresent shoulder malalignment 1, 2
• Radiography is the preferred initial study for delineating fractures and shoulder alignment 1

Advanced Imaging Indications

• CT is superior for characterizing complex fracture patterns when surgical planning is needed 1, 2
• MRI without contrast effectively diagnoses most traumatic soft-tissue pathology including rotator cuff tears, labral tears, and bone loss 1, 2
• MR arthrography is the gold standard for intra-articular pathology but requires invasive procedure 1
• CT angiography is preferred if vascular compromise is suspected (diminished pulses, expanding hematoma, ischemia signs) 2

Immediate Surgical Referral Indications

The following require immediate orthopedic or surgical consultation: 1, 2, 6, 4

• Unstable or significantly displaced fractures
• Open fractures
• Neurological deficits
• Posterior sternoclavicular dislocations
• Any signs of vascular compromise
• Types IV, V, and VI AC joint injuries

Critical Pitfalls to Avoid

• Failing to obtain axillary or scapula-Y views leads to missed dislocations and AC joint injuries 1, 2, 6
• Performing supine rather than upright radiographs underrepresents malalignment 1, 2
• Inadequate neurovascular examination documentation, particularly in high-energy trauma 2
• Underestimating AC joint injury severity based on AP views alone 2, 6
• Delaying surgical referral when indicated, which makes stabilization more technically challenging 6