Can a Magnetic Resonance Imaging (MRI) of the lumbar spine be performed in a patient with a previous 2-level lumbar fusion?

MRI of the Lumbar Spine Can Be Performed in Patients with Previous Lumbar Fusion

Yes, MRI of the lumbar spine can be performed safely and effectively in patients with previous 2-level lumbar fusion, though there are important considerations regarding image quality and alternative imaging options when necessary. 1

Imaging Options for Post-Fusion Patients

MRI Considerations

• MRI without and with contrast is the preferred imaging modality for evaluating:

  • Recurrent or residual disc herniations
  • Nerve root compression
  • Arachnoiditis
  • Infection
  • Soft tissue complications 1, 2

• Key advantages of MRI:

  • Accurately distinguishes recurrent/residual disc herniations from scar tissue
  • Evaluates nerve root compression
  • Assesses soft tissue structures that CT cannot visualize well
  • Can detect adjacent segment pathology and paraspinal muscle changes 1, 2

• Limitations of MRI:

  • Metal artifacts from hardware may limit image quality
  • Some implants may not be MRI compatible (though most modern implants are MRI conditional) 1, 3

Alternative Imaging Options

When MRI is contraindicated or limited by artifacts:

1. CT without contrast:

   • Excellent for assessing osseous fusion
   • Can detect hardware failure, loosening, malalignment, or fracture
   • Equal to MRI for predicting significant spinal stenosis and excluding cauda equina impingement 1

2. CT myelography:

   • Useful for assessing patency of spinal canal/thecal sac
   • Safety advantage over MRI for patients with non-MRI compatible implants
   • Sometimes more accurate in diagnosing nerve root compression in lateral recess
   • Disadvantage: requires lumbar puncture for intrathecal contrast injection 1

3. Plain radiographs:

   • Complementary to advanced imaging
   • Helpful for evaluating alignment and hardware integrity
   • Flexion-extension views can assess for abnormal motion/dynamic mobility 1

4. SPECT or SPECT/CT:

   • Not recommended as initial imaging
   • May be useful as an adjunct in cases of painful pseudarthrosis or periprosthetic loosening
   • Limited sensitivity (50%) but good specificity (93%) for detecting pseudarthrosis 1

Clinical Algorithm for Imaging Selection

1. First-line imaging: MRI without and with contrast

   • Best for evaluating soft tissue complications and distinguishing disc herniations from scar tissue
   • Use when infection, recurrent disc herniation, or nerve compression is suspected 1, 2

2. If hardware artifacts significantly limit MRI quality:

   • Consider CT without contrast for bony fusion assessment
   • Or CT myelography for neural compression evaluation 1

3. If patient has non-MRI compatible implants:

   • CT myelography is the best alternative
   • Plain radiographs with flexion-extension views as complementary imaging 1

4. For suspected pseudarthrosis with equivocal findings:

   • Consider SPECT/CT as an adjunctive study 1

Important Considerations

• Titanium implants produce fewer artifacts on MRI compared to stainless steel implants, allowing for better visualization of the spinal canal 3
• Modern MRI sequences can reduce metal artifacts and improve image quality in post-fusion patients
• The diagnostic value of MRI remains high despite potential artifacts, particularly for evaluating soft tissue complications 1, 2

Pitfalls to Avoid

• Don't assume MRI cannot be performed just because a patient has hardware - most modern spinal implants are MRI conditional
• Don't rely solely on plain radiographs for evaluating post-fusion complications, as they have limited sensitivity for detecting pseudarthrosis and soft tissue pathology
• Don't forget to obtain contrast-enhanced MRI when infection or recurrent disc herniation is suspected, as it significantly improves diagnostic accuracy 1, 2