When is a CT (Computed Tomography) scan of the hip recommended?

When is a CT Scan of the Hip Recommended?

CT hip without IV contrast is recommended as the next imaging study after negative or indeterminate radiographs when clinical suspicion for hip fracture persists in patients with acute traumatic hip pain. 1

Primary Indication: Occult Hip Fracture Detection

Order CT hip without IV contrast immediately after negative radiographs when:

• Patient has acute traumatic hip pain following a fall or minor trauma 1
• Clinical examination suggests fracture (inability to bear weight, pain with hip rotation, groin tenderness) despite normal X-rays 2
• Rapid diagnosis is critical to reduce fracture-related morbidity and mortality 1

The American College of Radiology emphasizes that CT's speed advantage over MRI (which may not be available within 24 hours) makes it the preferred next step when fracture is suspected, as rapid diagnosis decreases immobility time and reduces risk of osteonecrosis. 1

Diagnostic Performance

CT demonstrates strong diagnostic accuracy:

• Sensitivity: 94% for detecting radiographically occult hip fractures 1, 2
• Specificity: 100% 1, 2
• Detects occult fractures in 24.1% of patients with negative radiographs 1
• Changes management in 20% of cases 1

The American College of Radiology notes that approximately 39% of patients with negative radiographs ultimately have surgical hip fractures, making advanced imaging essential. 1

Secondary Indication: Surgical Planning

CT is also appropriate for characterizing known fractures:

• Non-displaced femoral neck fractures requiring surgical decision-making (arthroplasty versus percutaneous pinning) 1
• Trochanteric fractures needing detailed morphology assessment 1
• CT altered surgical decisions in 21% of non-displaced femoral neck fractures 1

Technical Specifications

Always order CT WITHOUT IV contrast:

• No evidence supports CT with IV contrast for acute traumatic hip pain 1
• No evidence supports CT without and with IV contrast 1
• Contrast adds unnecessary cost and risk without diagnostic benefit 3

Critical Pitfalls to Avoid

Do not delay CT by obtaining additional radiographic views:

• The American College of Radiology found that increasing the number of radiographic projections does not decrease the need for CT 1
• Proceed directly to CT when clinical suspicion persists 2

Recognize CT limitations:

• If CT is negative or equivocal but clinical suspicion remains high, proceed to MRI 1
• MRI has near 100% sensitivity and detects additional pelvic fractures in 38% of cases 1, 3
• CT may miss up to 6-21% of occult fractures that MRI would detect 1

Do not use bone scan:

• Insufficient evidence supports bone scan for acute traumatic hip pain evaluation 1, 2
• Bone scans are time-consuming and may be falsely negative for up to 72 hours 1

Clinical Algorithm

Follow this stepwise approach:

1. Initial imaging: AP pelvis and lateral hip radiographs for all patients with acute traumatic hip pain 1, 2, 4

2. If radiographs negative but fracture suspected: Order CT hip without IV contrast immediately 1, 2

3. If CT negative but clinical suspicion persists: Proceed to MRI hip without IV contrast 1

4. For known fractures needing characterization: CT without IV contrast for surgical planning 1, 3

Post-Surgical Context

CT is also indicated for pain after hip pinning:

• First-line advanced imaging after negative radiographs in patients with pain following hip fracture surgery 3
• Detects hardware complications (loosening, malposition, periprosthetic fractures) 3
• Follow with MRI if soft tissue injury suspected 3