## Imaging of Occult Scaphoid Fractures **Key Point:** MRI is the gold standard for detecting occult (radiographically occult) scaphoid fractures in the acute setting due to its superior soft-tissue contrast and ability to visualize bone marrow edema. ### Imaging Modality Comparison | Modality | Sensitivity | Specificity | Timing | Advantages | Limitations | |----------|-------------|-------------|--------|------------|-------------| | **MRI** | 98–100% | 99% | Acute (within 24–48 hrs) | Detects marrow edema; no radiation; diagnoses associated injuries | Cost; availability; contraindications | | CT scan | 95–98% | 98% | 10–14 days | High sensitivity; good for displacement; faster than MRI | Radiation; less sensitive for early marrow edema | | Bone scan | 90–95% | 85% | 72 hrs onward | Detects metabolic activity | Delayed; lower specificity; radiation | | Ultrasound | 80–90% | Variable | Operator-dependent | Portable; no radiation | Operator-dependent; limited by soft tissue | | Plain radiographs | 70–80% (initial) | Variable | Immediate | Readily available | Misses 15–30% of fractures acutely | ### Clinical Approach **High-Yield:** In a patient with clinical suspicion of scaphoid fracture (pain in the anatomical snuffbox, positive scaphoid compression test) but negative initial plain radiographs: 1. **Acute setting (< 48 hrs):** MRI is preferred for definitive diagnosis and to guide early treatment. 2. **Subacute setting (10–14 days):** CT becomes more sensitive as fracture lines become visible. 3. **Delayed diagnosis (> 3 weeks):** Bone scan shows increased uptake due to healing response. **Clinical Pearl:** MRI detects bone marrow edema even before a fracture line is visible on CT, making it superior in the acute phase. This allows early immobilization and prevents complications like nonunion and AVN. **Mnemonic:** **MRI ACUTE** — MRI for Rapid, Early detection in Acute scaphoid injury. 
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