What is the best imaging test to evaluate lumbar hardware status in a patient with existing lumbar hardware and a history of lumbar surgery?

Best Imaging Test for Evaluating Lumbar Hardware Status

CT lumbar spine without IV contrast is the best imaging test to evaluate lumbar hardware status, as it optimally assesses hardware integrity, position, alignment, and osseous fusion. 1

Primary Imaging Modality: CT Without Contrast

CT without contrast excels at evaluating the specific hardware-related concerns:

• Hardware integrity assessment: CT detects hardware failure including prosthetic loosening, malalignment, and metallic fracture 1
• Osseous fusion evaluation: CT is highly effective for assessing bony fusion status 1
• Hardware position verification: CT provides detailed osseous margins and trajectory visualization 1
• Alignment assessment: CT accurately evaluates spinal alignment in the presence of hardware 1

The American College of Radiology specifically states that CT without contrast is equal to MRI for predicting significant spinal stenosis and excluding cauda equina impingement, while providing superior hardware visualization 1

Complementary Role of Plain Radiographs

Radiographs should be obtained as a complementary study, not as the sole imaging:

• Functional assessment: Upright radiographs provide useful information about axial loading that CT cannot 1
• Dynamic evaluation: Flexion-extension views assess for abnormal motion or increased dynamic mobility suggesting pseudoarthrosis 1
• Hardware integrity screening: Radiographs help evaluate alignment and hardware integrity, though with limitations 1

Critical pitfall: Plain radiographs alone have only 64-69% accuracy for detecting complications with significant interobserver variability, making them insufficient as the sole imaging modality 2

When to Add MRI (With and Without Contrast)

MRI becomes the preferred modality when evaluating soft tissue complications rather than hardware itself:

• New neurologic symptoms: MRI with and without contrast accurately distinguishes recurrent disc herniation from postoperative scar tissue 1, 2
• Suspected infection: Contrast-enhanced MRI identifies and evaluates infection extent, including epidural abscess 1, 2
• Nerve root compression: MRI evaluates neural compression and arachnoiditis in post-surgical patients 1, 2

Important consideration: Modern titanium hardware is MRI-safe at 1.5T or less, contrary to common misconceptions 2

CT Myelography as Alternative

CT myelography serves as the preferred alternative when MRI quality is compromised:

• Severe metallic artifact: When hardware creates significant MRI artifact limiting diagnostic quality, CT myelography becomes the alternative of choice 1, 2
• Neural compression assessment: CT myelography is occasionally more accurate than MRI for diagnosing nerve root compression in the lateral recess 1
• MRI contraindications: CT myelography provides safety advantages for patients with non-MRI-safe implanted devices 1

Trade-off: CT myelography requires lumbar puncture for intrathecal contrast injection, which is a disadvantage compared to non-invasive imaging 1

Adjunctive Nuclear Medicine Imaging

SPECT or SPECT/CT has limited but specific utility:

• Pseudoarthrosis evaluation: SPECT/CT may be an adjunct for painful pseudoarthrosis or periprosthetic loosening in patients with previous fusion 1
• Not for initial assessment: These modalities are not appropriate for initial imaging 1

Clinical Algorithm for Hardware Evaluation

For hardware integrity concerns (loosening, fracture, position):

1. Start with CT lumbar spine without contrast 1
2. Add plain radiographs (including flexion-extension views) for functional assessment 1

For new neurologic symptoms after hardware placement:

1. Obtain MRI lumbar spine without and with contrast 1, 2
2. If MRI quality is limited by artifact, proceed to CT myelography 1, 2

For suspected infection:

1. MRI lumbar spine without and with contrast is preferred 1, 2
2. CT with contrast can assess for epidural abscess if MRI unavailable 1

Key Pitfalls to Avoid

• Do not assume MRI is contraindicated: Modern titanium constructs are MRI-compatible at 1.5T or less 2
• Do not rely on radiographs alone: They miss significant complications and have poor interobserver reliability 2
• Do not skip contrast in post-surgical patients with new symptoms: Contrast is essential for distinguishing scar from recurrent pathology 2
• Do not order CT with contrast for hardware evaluation: Contrast provides no additional benefit for assessing hardware or bony fusion 1