What is the preferred imaging modality, Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scan, for a patient with a metal plate on the humerus?

Imaging for Metal Plate on Humerus: CT is Superior to MRI

CT is the preferred imaging modality for evaluating a patient with a metal plate on the humerus, as it provides superior bone detail and is less affected by metal artifacts than MRI. 1

Why CT Over MRI

Metal Artifact Considerations

• MRI produces severe metallic susceptibility artifacts from orthopedic hardware that obscure surrounding tissues, making it typically unsuitable for evaluating areas with metal implants 2, 1
• CT is specifically recommended by the American College of Radiology when MRI assessment is limited by artifact from previously placed proximal humeral hardware 1
• While both modalities experience metal artifacts, CT maintains better visualization of bone and can be optimized with technical adjustments 2

CT's Specific Advantages with Hardware

• CT is the best modality for characterizing fracture patterns, hardware positioning, and bone healing around metal implants 2, 1
• CT provides excellent assessment of hardware loosening, fracture displacement, and heterotopic ossification 2
• Three-dimensional volume-rendered CT images can be obtained to better visualize complex anatomy despite hardware presence 2, 1

Optimizing CT Technique for Metal Hardware

• Use higher voltage (140 kVp) and higher exposure (200-400 mAs) with reduced pitch and slice overlap to improve image quality around metal 2
• Titanium hardware produces significantly less artifact than cobalt-chrome, allowing better bone detail visualization 3
• Modern dual-energy CT with virtual monochromatic imaging offers additional artifact reduction capabilities 4

Critical Limitation: Soft Tissue Evaluation

• CT cannot adequately assess rotator cuff tears, labral injuries, or cartilage damage—the most common sources of shoulder pain 1
• If soft tissue pathology evaluation is essential and MRI remains contraindicated, CT arthrography is the appropriate upgrade 1
• CT arthrography shows comparable sensitivity to MR arthrography for detecting labral lesions while maintaining superior osseous visualization 1

Alternative: Ultrasound for Soft Tissues

• When hardware artifacts limit MRI and soft tissue assessment is needed, ultrasound may be preferred over CT for evaluating rotator cuff pathology 5, 1
• Ultrasound provides radiation-free assessment of rotator cuff tears and biceps tendon pathology 1
• Ultrasound is particularly valuable when there is previously placed proximal humeral hardware that would create MRI artifacts 5

Common Pitfalls to Avoid

• Do not rely on CT alone if rotator cuff pathology is suspected—up to 40% of humeral fractures have associated rotator cuff tears that CT cannot detect 2, 6
• Avoid using projection interpolation metal artifact reduction (MAR) algorithms for quantitative measurements, as they can cause loss of detail and underestimation of lesion volumes 7
• Do not assume MRI is always superior—in the presence of metal hardware, MRI's soft tissue advantage is negated by severe artifacts 2, 1