How to diagnose a femur fracture?

Diagnosing Femur Fractures

Radiography is the gold standard for diagnosing femur fractures, with orthogonal views (anteroposterior and cross-table lateral) being the standard initial imaging approach. 1

Initial Imaging Approach

Standard Radiographic Views

• Anteroposterior (AP) view: With approximately 15 degrees of internal rotation
• Cross-table lateral view: Essential for improving overall sensitivity and assessing displacement
• AP view of the pelvis: Recommended to evaluate for associated pelvic fractures 1

When Standard Radiographs Are Negative or Equivocal

If clinical suspicion remains high despite negative radiographs, advanced imaging is indicated:

1. MRI without contrast: Nearly 100% sensitivity for occult fractures - first choice for suspected occult fractures 2
2. CT scan: 69-87% sensitivity - useful when MRI is contraindicated 2
3. Bone scintigraphy: Second-line diagnostic test for detecting fractures 1

Special Considerations for Different Fracture Types

Atypical Femur Fractures

Atypical femur fractures have distinct radiographic features:

• Located between the lesser trochanter and distal supracondylar flare
• Transverse fracture line originating at the lateral cortex
• Minimal or no comminution
• "Beaking" or "flaring" (localized periosteal or endosteal thickening) at the fracture site 1

Radiography has 90-95% sensitivity and 68-100% specificity for detecting these fractures. Consider imaging the contralateral femur as bilateral involvement occurs in up to 30% of cases. 1

Ipsilateral Femoral Neck Fractures with Shaft Fractures

These are frequently missed (20-50% initially) and require a specific protocol:

• Dedicated AP internal rotation plain radiograph
• Fine-cut (2-mm) CT scan through the femoral neck
• Intraoperative fluoroscopic lateral radiograph prior to fixation 3

Incomplete Fractures

For incomplete atypical femur fractures:

• CT is useful for discerning the presence of lucency in incomplete fractures
• MRI can determine the presence of radio-occult stress-related changes and define the extent of cortical involvement 1

Clinical Presentation Indicators

• Pain in the groin or thigh
• Inability to bear weight on the affected extremity
• Displaced fractures present with external rotation and abduction
• Shortened appearance of the affected leg 4

Pitfalls to Avoid

1. Missing associated fractures: Always evaluate the entire femur, including the femoral neck and pelvis
2. Inadequate views: Ensure proper orthogonal views are obtained
3. Overlooking occult fractures: Use advanced imaging when clinical suspicion is high despite negative radiographs
4. Failing to recognize atypical fractures: Look for the "dreaded black line" on the lateral cortex in patients on long-term bisphosphonates 5
5. Delayed diagnosis: Implement a systematic approach for patients with femoral shaft fractures to avoid missing associated femoral neck fractures 3

By following this diagnostic algorithm, clinicians can accurately diagnose femur fractures and provide appropriate treatment to reduce morbidity and mortality associated with these injuries.