Initial Imaging for the Shoulder
Standard radiography is the most appropriate initial imaging study for shoulder evaluation, consisting of at least three views: anteroposterior (AP) projections in internal and external rotation plus an axillary or scapula-Y view, performed with the patient upright. 1, 2
Radiographic Protocol
The essential radiographic series includes:
- AP views in internal and external rotation to assess the glenohumeral joint, humeral head, and glenoid 1, 2
- Axillary or scapula-Y view as the third mandatory projection, since AP views alone can misclassify acromioclavicular and glenohumeral dislocations 1
- Upright positioning is critical because supine radiography can underrepresent shoulder malalignment 1
This three-view minimum effectively demonstrates fractures, dislocations, and shoulder malalignment in the vast majority of cases 2. The anteroposterior view detects approximately 88% of shoulder injuries, while the oblique apical and lateral views capture specific injuries that may be missed on AP alone, including glenohumeral dislocations and certain clavicular and scapular fractures 3.
Clinical Context Matters
The radiographic approach should be tailored based on clinical presentation:
- For trauma or suspected dislocation: The standard three-view series is mandatory before any manipulation attempt 1
- For post-arthroplasty monitoring: Radiography remains the primary modality, typically obtained 3-6 weeks post-surgery and at regular intervals thereafter 4
- For stable, atraumatic shoulder pain: Plain radiographs are still the first step, though ultrasound may follow if radiographs are noncontributory 5
When to Consider Advanced Imaging
MRI or MR arthrography should only be pursued after radiographs are obtained and prove noncontributory 2:
- MRI without contrast (when soft tissue injury is suspected but radiographs are normal) 2
- MR arthrography (for suspected labral tears or instability when surgery is being considered) 5, 6
- CT scan for better characterization of complex fracture patterns identified on radiographs 2
Critical Pitfalls to Avoid
- Never rely on AP view alone—orthogonal views are essential to prevent missed dislocations 1, 2
- Avoid supine imaging when upright positioning is feasible, as it reduces diagnostic accuracy 1
- Do not skip radiographs and proceed directly to MRI or ultrasound, even when soft tissue pathology is suspected 4, 7
- Ensure adequate views are obtained; inadequate imaging leading to missed fracture components is a common error 2