Can you have a Magnetic Resonance Imaging (MRI) scan with metal screws in the foot?

MRI Safety with Metal Screws in the Foot

MRI scanning is generally safe for patients with titanium or stainless steel screws in the foot, as these implants are considered MR conditional and pose minimal risk at standard magnetic field strengths of 1.5T and 3T.

Safety Considerations for MRI with Metal Implants

Metal Implant Compatibility

• Modern orthopedic implants, including plates and screws used in foot surgery, are typically made of either titanium alloy or stainless steel, both of which have been extensively tested for MRI compatibility 1
• Research shows that standard orthopedic screws exhibit only minor magnetic field interactions:
  • Titanium alloy implants show an average deflection angle of only 4.3°
  • Stainless steel implants show an average deflection angle of 7.7°
  • Both are well below the 45° threshold considered safe 1

Temperature Changes

• MRI-related heating is minimal with foot screws:
  • Titanium alloy implants: average temperature increase of only 0.48°C
  • Stainless steel implants: average temperature increase of only 0.74°C 1
  • A study of cannulated screws (commonly used in foot surgery) showed maximum temperature changes of only 2.1°C at 1.5T and 2.4°C at 3T 2

Image Quality Considerations

Artifact Management

• Metal implants do create susceptibility artifacts that may affect image quality:
  • Fast Spin Echo (FSE) sequences produce the smallest artifacts
  • Diffusion-weighted imaging (DWI) produces the largest artifacts 1
  • Gradient Echo sequences also produce significant artifacts, with maximum artifact size extending approximately 20mm from the implant 2

Optimizing Image Quality

• Several techniques can minimize metal artifacts:
  • Use FSE and STIR sequences rather than gradient echo or DWI sequences
  • Increase bandwidth
  • Decrease field of view (FOV)
  • Optimize echo train length 1
  • Use metal artifact reduction sequences if available

Clinical Decision Making

When to Proceed with MRI

1. Confirm implant material - Most modern foot screws are made of titanium alloy or surgical stainless steel, which are MR conditional
2. Consider field strength - 1.5T scanners produce fewer artifacts than 3T scanners
3. Evaluate diagnostic goals - Determine if the area of interest is sufficiently distant from the implant to avoid significant artifact interference

Alternative Imaging Options

• If MRI is contraindicated or artifacts would significantly limit diagnostic value:
  • CT scan is an excellent alternative for evaluating bony structures 3
  • Ultrasound can be useful for evaluating soft tissue structures, especially when looking for foreign bodies or soft tissue infections 3

Special Considerations

Historical Context

• Older literature (pre-2000) was more cautious about MRI with metallic implants, but modern research confirms safety 4, 5
• Even long metallic constructs (up to 430mm) have been proven safe for MRI at both 1.5T and 3T 6

Patient Positioning

• Patients with metallic foot implants should be positioned in the standard supine position during MRI scanning 6

Conclusion

Patients with metal screws in the foot can safely undergo MRI examinations at standard field strengths (1.5T and 3T), though image quality may be affected by artifacts in the immediate vicinity of the implants. The benefits of obtaining important diagnostic information through MRI typically outweigh the minimal risks and artifact limitations in most clinical scenarios.