Is a SPECT (Single Photon Emission Computed Tomography) scan with CT (Computed Tomography) medically necessary for a patient status post lumbar spinal fusion with ongoing low back pain and a history of infection?

SPECT/CT for Post-Lumbar Fusion Pain: Medical Necessity Assessment

SPECT/CT is NOT medically necessary as the initial imaging study for this patient, but MRI lumbar spine without contrast should be ordered first to evaluate for infection, hardware complications, and soft tissue pathology given the recent hardware removal and positive infection culture. 1

Why SPECT/CT Does Not Meet Current Indications

The patient's clinical scenario does not satisfy the Aetna criteria listed in the authorization request. Specifically:

• Osteomyelitis assessment criterion NOT MET: While the patient had a prior positive culture from hardware removal, he completed 12 weeks of antibiotics and the current question is ongoing pain evaluation, not active infection differentiation 1
• The ACR Appropriateness Criteria do not support SPECT/CT as initial imaging for post-fusion pain evaluation in adults 1

Recommended Imaging Algorithm

First-Line Imaging: MRI Lumbar Spine Without Contrast

MRI without contrast is the appropriate initial advanced imaging study for this clinical presentation because: 1

• Superior soft tissue evaluation: MRI directly visualizes epidural abscess, residual/recurrent infection, and paraspinal soft tissues that could explain focal pain 1
• Hardware assessment: MRI can evaluate for hardware-related complications despite metallic artifact 1
• Fusion assessment: MRI is equal to CT for evaluating spinal stenosis and neural impingement 1

Clinical Red Flags Present in This Case

This patient demonstrates multiple concerning features that mandate cross-sectional imaging: 1

• Constant pain (6/10 VAS, described as stabbing/aching)
• Night pain (keeps him awake)
• Recent documented infection (positive hardware cultures)
• Pain duration >4 weeks (ongoing since hardware removal)

When SPECT/CT Would Be Appropriate

SPECT/CT serves as an adjunct imaging modality, not initial imaging, in specific post-fusion scenarios: 1

• Painful pseudarthrosis evaluation: When MRI and CT are equivocal for fusion status and clinical suspicion remains high 2, 3
• Hardware loosening assessment: To detect metabolically active pedicle screw loosening when CT shows questionable findings 4, 5
• Adjacent segment degeneration: When conventional imaging cannot definitively localize the pain generator 5

The evidence shows SPECT/CT reclassifies 45% of lesions compared to planar scintigraphy alone and increases specificity for detecting nonunion of interbody devices 2, 5. However, this benefit applies after initial cross-sectional imaging has been performed.

Practical Clinical Pathway

Step 1: Order MRI lumbar spine without contrast 1

• Evaluates for residual/recurrent infection (epidural abscess, discitis)
• Assesses fusion mass integrity
• Identifies neural compression or soft tissue pathology

Step 2: If MRI is contraindicated or shows significant artifact from hardware 1

• Consider CT myelography for neural compression assessment
• CT without contrast can evaluate bony fusion and hardware integrity

Step 3: If MRI/CT show solid fusion but pain persists 1, 2, 3

• Then SPECT/CT becomes appropriate to evaluate for:
  • Metabolically active pseudarthrosis
  • Occult hardware loosening
  • Adjacent segment disease

Critical Pitfalls to Avoid

• Do not skip MRI in a patient with recent documented infection: The positive hardware culture from the recent removal procedure creates ongoing infection risk that only MRI can adequately assess 1
• SPECT/CT cannot evaluate soft tissue infection: It shows bone metabolism but cannot distinguish infection from mechanical pain generators without anatomic correlation 2, 3
• Insurance denial is predictable: The Aetna criteria explicitly require specific indications, none of which are met in this case as presented

Documentation Needed for Future SPECT/CT Authorization

If MRI/CT are performed and SPECT/CT becomes clinically indicated, documentation should include: 2, 3, 5

• Solid fusion confirmed on CT or MRI
• Persistent focal pain despite conservative management
• Equivocal findings on anatomic imaging requiring metabolic correlation
• Specific clinical question (pseudarthrosis vs. hardware loosening vs. adjacent segment disease)