A 68-year-old woman presents to the emergency department with severe pain in the right hip and groin following a fall at home. On examination, the right lower limb is held in external rotation and flexion. Plain radiographs of the pelvis and right hip are inconclusive. What is the investigation of choice to confirm the diagnosis of femoral neck fracture?

## Investigation of Choice for Femoral Neck Fracture ### Clinical Context Femoral neck fractures are common in elderly patients, particularly women with osteoporosis. While plain radiographs are the first-line imaging, they may miss non-displaced or stress fractures due to the complex anatomy and overlapping bony structures of the hip region. ### Why MRI is the Gold Standard **Key Point:** MRI is the most sensitive and specific investigation for detecting femoral neck fractures, especially non-displaced fractures that may not be visible on plain radiographs. **High-Yield:** MRI has a sensitivity of >95% for femoral neck fractures and can detect fractures within 24–48 hours of injury, even when plain X-rays are negative. It provides excellent soft tissue contrast and can assess for associated injuries (labral tears, ligamentous injuries). **Clinical Pearl:** In elderly patients with high clinical suspicion of femoral neck fracture but negative plain radiographs, MRI should be obtained urgently to guide management decisions. Early diagnosis prevents complications such as avascular necrosis (AVN) due to delayed treatment. ### Comparison of Modalities | Investigation | Sensitivity | Specificity | Advantages | Disadvantages | |---|---|---|---|---| | Plain X-ray | 80–90% | High | First-line, quick, low cost | Misses non-displaced fractures | | MRI | >95% | >95% | Detects non-displaced fractures, no radiation, assesses soft tissue | Expensive, time-consuming, contraindicated in some patients | | CT scan | 90–95% | High | Good for complex fractures, surgical planning | Radiation exposure, less soft tissue detail | | Bone scan | 85–90% | Moderate | Detects stress fractures early | Delayed imaging (24–72 hrs), poor anatomical detail | **Tip:** In clinical practice, if plain radiographs are negative but clinical suspicion is high (pain, inability to bear weight, positive FABER test), proceed directly to MRI rather than waiting for delayed bone scan imaging. [cite:Campbell's Operative Orthopaedics 13e Ch 56]