Would you order an MRI for a patient with recurrent back pain and a history of L4-L5 discectomy, despite unchanged mild facet osteoarthritis (OA) on repeat X-ray?

MRI for Post-Discectomy Recurrent Back Pain

For a patient with recurrent back pain following L4-L5 discectomy and unchanged mild facet osteoarthritis on X-ray, an MRI of the lumbar spine without contrast is indicated to evaluate for potential recurrent disc herniation or other soft tissue abnormalities.

Rationale for MRI in Post-Discectomy Patients

X-rays have significant limitations in evaluating post-surgical back pain:

• X-rays primarily show bony structures but cannot adequately visualize soft tissues including disc material, nerve roots, or epidural scarring 1
• X-rays have limited sensitivity (19%-72%) for many spinal pathologies 1
• Unchanged mild facet OA on X-ray does not explain persistent symptoms, suggesting another cause

Key considerations for ordering MRI:

1. Post-surgical status: Patients with prior discectomy have higher risk of recurrent disc herniation
2. Persistent symptoms: The patient remains symptomatic despite X-ray findings being unchanged
3. Appropriate timing: The American College of Radiology recommends MRI for back pain persisting beyond 6 weeks of conservative management 2

Clinical Decision Algorithm

1. For post-discectomy patients with recurrent back pain:

   • If symptoms are mild and improving → Conservative management
   • If symptoms persist > 6 weeks despite conservative care → MRI lumbar spine without contrast
   • If red flags present (progressive neurological deficits, cauda equina symptoms) → Immediate MRI

2. MRI protocol selection:

   • Standard: MRI lumbar spine without contrast (preferred for most cases)
   • Add contrast only if suspecting infection, malignancy, or to differentiate scar tissue from recurrent herniation

Benefits of MRI in This Clinical Scenario

MRI provides superior evaluation of:

• Recurrent disc herniation (common after discectomy)
• Post-surgical changes including epidural fibrosis
• Neural compression or irritation
• Facet joint inflammation not visible on X-ray
• Soft tissue abnormalities including disc degeneration and nerve root compression 1

Important Caveats

• MRI findings must be correlated with clinical symptoms, as anatomical abnormalities are common in asymptomatic individuals 3
• Substituting MRI for X-rays may increase costs and potentially lead to more spine operations without necessarily improving outcomes 4
• MRI should be targeted to the area of interest (lumbar spine) rather than complete spine imaging 5

Follow-up Recommendations

• If MRI reveals recurrent disc herniation consistent with symptoms → Consider surgical consultation
• If MRI shows only post-surgical changes without neural compression → Focus on conservative management
• If MRI is negative → Consider other causes of pain (myofascial, referred pain, psychosocial factors)

The high-quality soft tissue visualization provided by MRI makes it the appropriate next step for evaluating persistent symptoms in this post-surgical patient when X-rays have not revealed a clear explanation for ongoing pain.