What is the best imaging modality for a patient with a history of back surgery?

Imaging for Patients with Prior Back Surgery

For patients with a history of back surgery presenting with new or progressive symptoms, order MRI lumbar spine without and with IV contrast as the initial imaging study. 1

Primary Recommendation: MRI with Contrast

MRI lumbar spine without and with IV contrast is the gold standard for post-surgical spine evaluation because it accurately distinguishes recurrent or residual disc herniations from postoperative scar tissue—a critical distinction that directly impacts surgical decision-making. 1, 2

Key Advantages of Contrast-Enhanced MRI:

• Differentiates scar from recurrent disc herniation: Scar tissue enhances with gadolinium contrast while disc material does not, making this distinction possible only with contrast administration 1, 2
• Evaluates nerve root compression and arachnoiditis in patients with new or progressive symptoms after previous surgery 1
• Identifies and evaluates extent of infection, including epidural abscess, which is a critical consideration in post-surgical patients 1
• Superior soft-tissue resolution allows assessment of the spinal canal, neural foramina, and subarticular recesses 1, 3

Alternative Imaging Options

CT Lumbar Spine Without Contrast

Use CT without contrast when evaluating hardware integrity and bony fusion status. 1

• Optimal for assessing osseous fusion and detecting hardware failure including prosthetic loosening, malalignment, or metallic fracture 1
• Equal to MRI for predicting significant spinal stenosis and excluding cauda equina impingement 1
• Consider adding IV contrast only if epidural abscess is suspected in the clinical context 1

CT Myelography

Reserve CT myelography for specific scenarios where MRI is contraindicated or inadequate. 1

• Useful when metallic hardware creates significant MRI artifact that limits diagnostic quality 1
• Safety advantage for patients with non-MRI-safe implanted medical devices 1
• Occasionally more accurate for diagnosing nerve root compression in the lateral recess compared to MRI 1
• Major disadvantage: requires lumbar puncture with intrathecal contrast injection 1

Plain Radiography

Obtain upright radiographs as a complementary study, not as initial imaging. 1

• Helpful for evaluating alignment and hardware integrity in patients with new or progressive symptoms 1
• Upright views provide functional information about axial loading that cross-sectional imaging cannot 1
• Flexion-extension views can detect abnormal motion or increased dynamic mobility suggesting instability 1

Clinical Algorithm for Decision-Making

Step 1: Determine Primary Clinical Question

• If evaluating new radicular symptoms or suspected recurrent disc herniation: Order MRI without and with contrast 1, 2
• If evaluating hardware integrity or fusion status: Order CT without contrast 1
• If red flags for infection present (fever, elevated inflammatory markers): Order MRI without and with contrast 1

Step 2: Consider Patient-Specific Factors

• MRI contraindicated or non-MRI-safe hardware present: Order CT myelography 1
• Severe metallic artifact limiting MRI interpretation: Consider CT myelography as complementary study 1
• Concern for pseudoarthrosis or hardware loosening: Consider SPECT/CT as adjunct to CT 1

Step 3: Correlation with Surgical History

• Anterior approach surgeries: Contrast less routinely needed as epidural space rarely transgressed 1
• Posterior approach surgeries: Contrast beneficial for discriminating recurrent disc from scar 1

Critical Pitfalls to Avoid

Do not order MRI with contrast alone (without the non-contrast sequences)—interpretation requires correlation with standard non-contrast sequences. 1

Do not assume MRI without contrast is sufficient in post-surgical patients—you will miss the critical scar versus recurrent disc distinction. 1, 2

Do not order whole-body bone scan, FDG-PET/CT, or discography for routine post-surgical evaluation—these have no established role in this clinical scenario. 1

Beware of titanium versus stainless steel hardware: Titanium implants produce fewer MRI artifacts and may allow better imaging quality. 4

Evidence Quality Note

The 2021 ACR Appropriateness Criteria represent the most authoritative and recent guideline evidence for this clinical scenario, specifically addressing "Variant 5: Low back pain with history of prior lumbar surgery and with or without radiculopathy." 1 This recommendation is reinforced by research demonstrating that contrast-enhanced MRI successfully identifies the cause of failed back surgery syndrome in the majority of cases, with recurrent disc herniation and epidural scar being the most common findings. 2, 5