Can patients with knee prostheses undergo Magnetic Resonance Imaging (MRI)?

MRI for Patients with Knee Prostheses

Yes, patients with knee prostheses can undergo MRI when appropriate metal artifact reduction techniques are used. 1

Indications for MRI in Knee Prosthesis Patients

MRI with metal artifact reduction techniques is indicated for evaluating:

• Periprosthetic soft-tissue abnormalities 1
• Quadriceps or patellar tendinopathy 1
• Arthrofibrosis 1
• Patellar clunk syndrome 1
• Periarticular soft-tissue masses 1
• Aseptic loosening or osteolysis (when infection has been excluded) 1

Technical Considerations

When performing MRI on patients with knee prostheses:

• Use robust metal reduction techniques to minimize artifacts 1
• Non-contrast MRI is typically sufficient and preferred 2
• Contrast administration is generally unnecessary for most post-arthroplasty evaluations 1, 2
• Specialized pulse sequences can result in substantial metallic artifact reduction 3

Diagnostic Value

MRI offers several advantages for evaluating knee prostheses:

• Allows comprehensive evaluation of tissues surrounding knee arthroplasty implants 3
• Provides excellent visualization of bone, implant-tissue interfaces, and periprosthetic soft tissue 3
• Shows high reproducibility and accuracy for diagnosing infection, loosening, wear, and malalignment 4
• Can detect osteolysis not visible on radiographs 1

Clinical Algorithm for Imaging After Total Knee Arthroplasty

1. Initial evaluation: Plain radiography is the appropriate first-line imaging for all patients with knee prostheses 1

2. For suspected infection:

   • Image-guided aspiration is the next appropriate step 1
   • MRI may help detect extracapsular spread of infection and abscess formation 1

3. For suspected aseptic loosening/osteolysis/instability:

   • Either MRI without contrast or CT without contrast is appropriate 1
   • MRI with metal artifact reduction can detect osteolysis not visible on radiographs 1

4. For suspected periprosthetic fracture:

   • CT without contrast is the preferred next imaging study 1

5. For suspected soft-tissue abnormality:

   • Either ultrasound or MRI without contrast is appropriate 1
   • MRI is particularly valuable for evaluating quadriceps/patellar tendinopathy, arthrofibrosis, and patellar clunk syndrome 1

Common Pitfalls and Caveats

• Standard MRI sequences without metal artifact reduction will produce non-diagnostic images 3
• Radiographs should always be the initial imaging modality before proceeding to MRI 1
• MRI is not the first-line test for suspected periprosthetic infection 1
• The diagnostic value of MRI for instability, arthrofibrosis, or patellofemoral complaints remains limited and inconclusive in some studies 4
• MRI may not provide useful additional information in cases where the clinical diagnosis is already certain 5

By following these guidelines, MRI can be safely and effectively used in patients with knee prostheses to evaluate complications and guide appropriate management decisions.