## Imaging of Scaphoid Fractures **Key Point:** MRI is the most sensitive imaging modality for detecting occult scaphoid fractures, particularly in the acute phase (first 2 weeks), with sensitivity >95% and specificity >98%. ### Imaging Modality Comparison | Modality | Sensitivity (Acute) | Specificity | Advantages | Limitations | | --- | --- | --- | --- | --- | | **Plain X-ray** | 60–80% | High | Readily available; low cost | Misses non-displaced fractures; requires 10–14 days for callus visibility | | **MRI** | >95% | >98% | Detects bone marrow edema within hours; best for early diagnosis; no radiation | Expensive; not always immediately available; contraindicated with metallic implants | | **CT** | 90–95% | High | Better for displaced/comminuted fractures; useful for union assessment | Radiation exposure; less sensitive for early marrow edema than MRI | | **Bone scan** | 90% | Moderate | Detects metabolic activity; useful at 72 hours onwards | Delayed imaging (3–5 days); poor anatomical detail; radiation | **High-Yield:** In suspected scaphoid fractures with negative initial plain radiographs, **MRI is the gold standard** for early diagnosis. It detects bone marrow edema within hours of injury, before callus formation is visible on X-rays. **Clinical Pearl:** Many institutions use a **clinical decision rule**: if scaphoid fracture is clinically suspected (tenderness in scaphoid fossa, positive scaphoid compression test) but X-rays are negative, the patient is treated as a presumed fracture (immobilization) and re-imaged at 10–14 days. However, MRI can definitively rule in or rule out the fracture immediately. **Mnemonic:** **MIST** — **M**RI (most sensitive), **I**maging (early), **S**ensitivity (>95%), **T**rust it (gold standard for acute diagnosis). 
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