A 28-year-old male presents with wrist pain and swelling after a fall on an outstretched hand (FOOSH). Clinical examination reveals tenderness in the anatomical snuffbox and a positive scaphoid compression test. Initial plain radiographs (PA, lateral, and scaphoid views) appear normal. What is the investigation of choice to confirm the diagnosis?

## Investigation of Choice for Suspected Scaphoid Fracture with Normal Initial Radiographs ### Clinical Context The patient has classic clinical signs of scaphoid fracture (anatomical snuffbox tenderness, positive scaphoid compression test) but normal initial radiographs. This is a common scenario — up to 25% of scaphoid fractures are radiographically occult on initial imaging. ### Why MRI is the Best Choice **Key Point:** MRI is the gold standard investigation for detecting radiographically occult scaphoid fractures with the highest sensitivity (>95%) and specificity (>95%). **High-Yield:** MRI can: - Detect fractures within 24–48 hours of injury (before callus formation) - Assess fracture location, displacement, and comminution - Evaluate soft tissue injury (ligamentous injury, carpal instability) - Determine vascularity of the proximal pole (critical for prognosis) - Exclude other carpal injuries (lunate, triquetrum) ### Comparison Table: Imaging Modalities for Occult Scaphoid Fracture | Investigation | Sensitivity | Specificity | Timing | Advantages | Disadvantages | | --- | --- | --- | --- | --- | --- | | **MRI** | >95% | >95% | 24–48 hrs | Gold standard; assesses vascularity; soft tissue detail | Cost; time; contraindications | | **CT** | 90–95% | 95% | 48–72 hrs | High sensitivity; 3D reconstruction; faster than MRI | Radiation; less soft tissue detail | | **Repeat X-rays (10–14 days)** | 80–90% | High | 10–14 days | Cost-effective; widely available | Delayed diagnosis; fracture line becomes visible only after resorption | | **Bone scan** | 85–90% | 70–80% | 72 hrs | Detects metabolic activity | Poor specificity; radiation; cannot assess anatomy | **Clinical Pearl:** In a young, symptomatic patient with high clinical suspicion and normal initial radiographs, MRI is preferred because it: 1. Confirms the diagnosis immediately (avoiding 10–14 day delay) 2. Assesses proximal pole vascularity (determines union risk) 3. Detects associated injuries (scapholunate ligament tear, SLAC wrist) ### Mechanism of Radiographic Occultness Initial radiographs may be normal because: - The fracture line is non-displaced and perpendicular to the X-ray beam - Minimal callus formation in the first 10–14 days - Scaphoid's complex anatomy obscures the fracture on standard views **Mnemonic:** **MIST** for imaging occult scaphoid fractures: - **M**RI (first-line for immediate diagnosis) - **I**mmobilization (while awaiting imaging) - **S**caphoid views (repeat radiographs if MRI unavailable) - **T**iming (MRI within 48 hrs; repeat X-rays at 10–14 days) ### Why Not the Other Options? See the distractor section below.