Can a computed tomography (CT) scan of the spine differentiate between degenerative disc disease and compression fracture?

CT Differentiation of Degenerative Disc Disease vs. Compression Fracture

CT scans of the spine can effectively differentiate between degenerative disc disease and compression fractures through their distinct imaging characteristics, though MRI may provide superior soft tissue evaluation in certain cases. 1

Key Differentiating Features on CT

Compression Fracture Findings

• Fracture lines and deformity: CT provides detailed analysis of fractures extending to the posterior column of the vertebra 1
• Cortical disruption: Clear visualization of the integrity of pedicles and posterior cortex 1
• Vertebral height loss: Often acute and focal compared to gradual disc height loss in DDD
• Bony fragments: May show retropulsed bone fragments in the spinal canal 1
• Trabecular pattern disruption: Visible alteration of internal bone architecture

Degenerative Disc Disease Findings

• Disc space narrowing: Progressive loss of disc height
• Endplate sclerosis: Increased density of vertebral endplates
• Osteophyte formation: Bony outgrowths at vertebral margins
• Facet joint hypertrophy: Degenerative changes in posterior elements
• Vacuum phenomenon: Gas collection within disc spaces (pathognomonic for DDD)

Advantages of CT for Differentiation

1. Superior bony detail: CT provides excellent visualization of bony structures, making it ideal for fracture detection 1
2. Multiplanar capabilities: Modern CT with multiplanar reformats allows visualization in multiple planes 1
3. Hardware compatibility: Less affected by metallic artifacts compared to MRI 1
4. Equal to MRI: CT has been shown to be equal to MRI for predicting significant spinal stenosis 1

Limitations of CT for Differentiation

1. Soft tissue contrast: Limited compared to MRI for assessing disc material, ligaments, and neural elements 1
2. Radiation exposure: Higher radiation dose compared to plain radiographs
3. Acuity assessment: Cannot reliably determine the age of compression fractures without bone marrow edema visualization 1

When MRI May Be Preferred

• Determining fracture acuity: MRI can detect bone marrow edema, indicating acute fractures 1
• Neural compromise: Better visualization of spinal cord and nerve root compression 1
• Malignant vs. benign fractures: MRI can help distinguish between pathologic and osteoporotic fractures 1
• Soft tissue pathology: Superior for evaluating disc herniations and ligamentous injuries 1

Clinical Algorithm for Imaging Selection

1. Initial evaluation: Begin with plain radiographs in patients with suspected compression fracture, especially those with history of osteoporosis or steroid use 2

2. When to use CT without contrast:

   • Need for detailed fracture characterization
   • Assessment of posterior elements involvement
   • Patients with contraindications to MRI
   • Evaluation of spinal hardware

3. When to use MRI without contrast:

   • Need to assess fracture acuity
   • Evaluation of bone marrow edema
   • Concern for neural compromise
   • Suspected soft tissue injury

4. Consider MRI with contrast when:

   • Suspicion for underlying malignancy
   • Concern for infection or inflammation
   • Need to distinguish between malignant and benign compression fractures 2

Pitfalls to Avoid

• Misinterpreting chronic compression fractures: Old compression fractures may show sclerotic changes that can mimic degenerative changes
• Overlooking subtle fractures: Incomplete fractures may be difficult to detect without proper windowing
• Confusing vacuum phenomenon: Gas within disc spaces indicates degenerative changes, not fracture
• Relying solely on CT for soft tissue pathology: Consider complementary MRI when soft tissue involvement is suspected

CT scanning remains an excellent modality for differentiating between degenerative disc disease and compression fractures, particularly when focusing on bony anatomy and structural changes, though MRI offers complementary information regarding soft tissues and fracture acuity.