Should a non-contrast computed tomography (CT) of the hip be obtained for a suspected hip fracture?

CT Without Contrast for Hip Fracture

Non-contrast CT of the hip should NOT be used as initial imaging for suspected hip fracture—plain radiographs (AP pelvis with cross-table lateral hip view) are the first-line study. However, non-contrast CT is appropriate as second-line imaging when radiographs are negative but clinical suspicion remains high, particularly when MRI is unavailable or contraindicated 1.

Initial Imaging Approach

Plain radiographs detect approximately 90% of proximal femoral fractures and remain the standard initial imaging modality 1. The recommended views include:

• AP pelvis view (allows contralateral comparison and detects associated pelvic fractures)
• Cross-table lateral view of the symptomatic hip
• Some institutions add a separate AP hip view

Radiographs are fast, portable, well-tolerated, and when positive, often require no additional imaging for treatment planning 1, 2.

Role of CT After Negative Radiographs

When to Use CT

CT without contrast serves as a problem-solving modality following negative radiographs for two specific purposes 1:

1. Detecting radiographically occult fractures
2. Better depicting fracture morphology for surgical planning

Diagnostic Performance

CT demonstrates high specificity (98%) but lower sensitivity (87%) compared to MRI for occult hip fractures 3. This means:

• CT rarely calls a fracture when none exists (few false positives)
• CT may miss some fractures that MRI would detect (more false negatives)

A meta-analysis found CT has an area under the ROC curve of 0.972, indicating excellent overall diagnostic accuracy, though sensitivity remains inferior to MRI's near 100% 3.

Practical Advantages of CT

CT offers significant practical benefits over MRI 4, 5, 6:

• Accessibility: Available 24/7 in most hospitals; MRI often has substantial delays
• Speed: Mean time to diagnosis with CT is 3 hours versus 40 hours when waiting for MRI 4
• Cost-effectiveness: An MRI-selective protocol (CT first, MRI only if CT negative) saved approximately €66,805 over 4 years in one study 4
• Reduced time to surgery: Implementation of CT-first protocols decreased time from ED arrival to surgery by 179 minutes (approximately 3 hours) without increasing mortality 7

CT Limitations and Pitfalls

Critical caveat: CT cannot completely exclude hip fracture 1, 5, 6. Studies report:

• Approximately 23% of patients with negative CT but continued suspicion had fractures confirmed on subsequent MRI 4
• One study documented a missed subcapital fracture on CT that was identified on MRI 6
• CT is particularly less reliable for femoral neck fractures compared to trochanteric fractures 8

If clinical suspicion remains high after negative CT, MRI should still be performed 4, 3.

MRI Remains the Gold Standard for Occult Fractures

When radiographs are negative but fracture is suspected, MRI without contrast is the preferred second-line imaging 1. MRI demonstrates:

• 99-100% sensitivity for proximal femoral fractures 1
• Ability to detect pelvic fractures and soft-tissue injuries
• Superior characterization of fracture morphology (e.g., detecting intertrochanteric extension of apparent isolated greater trochanter fractures)

The ACR Appropriateness Criteria explicitly state that MRI should be reserved for second-line imaging when radiographs are negative, not as a first-line modality 1.

Recommended Algorithm

1. Initial presentation: Obtain AP pelvis + cross-table lateral hip radiographs
2. If radiographs positive: Proceed to treatment (additional imaging usually unnecessary)
3. If radiographs negative but clinical suspicion persists:
   • First choice: MRI without contrast (if available within 24 hours)
   • Acceptable alternative: Non-contrast CT (if MRI unavailable/contraindicated or to expedite diagnosis)
4. If CT negative but suspicion remains: Obtain MRI to exclude fracture definitively

What NOT to Do

• Do not use contrast-enhanced CT—no evidence supports its use for acute hip fracture evaluation 1
• Do not use multiphase CT—no supporting literature 1
• Do not rely on CT alone to exclude fracture in high-risk patients with persistent symptoms 4, 3
• Do not delay imaging in elderly patients with hip pain after falls—early diagnosis reduces morbidity and mortality 1, 2

Clinical Context

Delays in hip fracture diagnosis beyond 12 hours significantly increase 30-day mortality 1. The choice between CT and MRI for occult fractures should balance diagnostic accuracy against institutional availability and time constraints. In real-world practice, obtaining a CT promptly is superior to waiting days for MRI, as long as providers understand CT's limitations and maintain appropriate clinical suspicion 4, 5, 6.