What advanced imaging modality is recommended for a patient with a history of shoulder replacement and hardware in the shoulder, presenting with pain after an injury?

Advanced Imaging for Post-Injury Shoulder Pain with Hardware in Place

Order radiographs first, followed by CT with metal reduction protocol if advanced imaging is needed; MRI will be severely limited by metallic artifacts from the shoulder replacement hardware. 1

Initial Imaging Approach

Start with standard radiographs as the first-line imaging modality for any patient with shoulder arthroplasty presenting with new pain after injury. 1 This should include:

• Anteroposterior views in internal and external rotation
• Axillary or scapula-Y view
• Upright positioning (malalignment can be underrepresented on supine films) 1

Radiographs are particularly effective for detecting periprosthetic fractures, including scapular fractures that can occur with relatively minor trauma in patients with shoulder prostheses. 1

When Advanced Imaging is Needed

CT is the Preferred Advanced Modality

If radiographs are negative or inconclusive but clinical suspicion remains high, order CT with metal reduction protocol. 1, 2

The American College of Radiology specifically recommends CT as the appropriate advanced imaging choice when:

• MRI cannot adequately assess the shoulder due to susceptibility artifacts from proximal humeral hardware 2
• Further characterization of periprosthetic fractures is needed (degree of displacement, extent, comminution) 1
• Occult fractures are suspected clinically but radiographs are negative 1

CT technical optimization is critical in the presence of hardware:

• Use higher voltage (140 kVp) and higher exposure (200-400 mAs) 2
• Apply metal artifact reduction protocols 1, 2
• Consider 3D reconstruction for better visualization of fracture displacement 2

Why MRI is Not Recommended

MRI produces severe metallic susceptibility artifacts from shoulder replacement hardware that obscure surrounding tissues, making it typically unsuitable for evaluating areas with metal implants. 2 The hardware creates significant image degradation that prevents adequate assessment of both bone and soft tissue structures.

Critical Limitations to Understand

What CT Can Evaluate Well:

• Periprosthetic fractures (including occult fractures) 1
• Hardware positioning and loosening 1, 2
• Bone healing and osteolysis 2
• Glenoid erosion and bone stock 3, 4

What CT Cannot Assess:

• Rotator cuff tears (common source of pain, especially in older adults) 2
• Labral injuries without arthrography 2
• Cartilage damage 2

Alternative Considerations

If Soft Tissue Evaluation is Essential:

Consider CT arthrography if soft tissue pathology must be evaluated and MRI remains contraindicated due to hardware artifacts. 2 CT arthrography provides:

• Comparable sensitivity to MR arthrography for labral lesions 2
• Improved visualization of osseous abnormalities 2
• Better soft tissue assessment than non-contrast CT 1

Ultrasound as Adjunct:

Ultrasound may be added specifically for rotator cuff evaluation if this is a clinical concern, as it can assess rotator cuff tears and biceps tendon pathology without radiation and is not affected by metallic hardware. 2, 5 However, ultrasound has limited utility for evaluating osseous pathology, which is the primary concern after trauma. 1

Common Pitfalls to Avoid

• Do not order MRI first in patients with shoulder replacement hardware—the artifacts will render the study non-diagnostic 2
• Do not rely on standard CT protocols—metal artifact reduction techniques are essential for adequate image quality 2
• Do not assume normal radiographs exclude fracture—occult periprosthetic fractures are common and CT may be needed even with negative plain films 1
• Remember CT's soft tissue limitations—if rotator cuff pathology is suspected as the pain source rather than hardware complications, ultrasound should be added to the workup 2, 5