In a patient with suspected occult hip fracture and a normal X-ray, which imaging modality is indicated next to best detect occult injury?

• A. CT scan of the hip
• B. MRI of the hip
• C. Ultrasound
• D. Repeat X-ray in 1 week

Answer: (C)

When there’s strong suspicion of a hip fracture but the X-ray is normal, the test that most reliably reveals an occult injury is MRI of the hip. MRI detects bone marrow edema and other changes that occur with a fracture even when the cortical bone hasn’t broken through or isn’t visible on X-ray. This makes MRI highly sensitive for identifying occult fractures early, allowing timely immobilization and treatment.

CT can show fracture lines and is useful if MRI isn’t available, but it’s generally less sensitive than MRI for nondisplaced or early fractures because it focuses on cortical disruption rather than marrow signal. Ultrasound isn’t helpful for diagnosing occult hip fractures since bone injury is best visualized with marrow changes rather than surface structures. Waiting a week to repeat X-ray might miss the injury altogether or delay crucial management.