## Distinguishing Scaphoid Fracture from Other Carpal Injuries ### The Scaphoid Fat Stripe Sign **Key Point:** The scaphoid fat stripe (also called the scaphoid fat pad sign) is a radiolucent line that normally appears on the posteroanterior (PA) radiograph lateral to the scaphoid. Disruption or absence of this line is highly suggestive of scaphoid fracture, even when the fracture line itself is not visible on initial plain films. **High-Yield:** This sign is particularly valuable in occult scaphoid fractures where the fracture line may not be radiographically apparent on day 1–2, but the swelling and haemorrhage within the scaphoid displace the fat pad, making it invisible or distorted. ### Why This Discriminates Scaphoid from Other Carpal Injuries | Feature | Scaphoid Fracture | Other Carpal Injuries (e.g., Lunate, Triquetrum) | |---------|-------------------|--------------------------------------------------| | Scaphoid fat stripe | Disrupted/absent | Preserved (unless direct soft tissue trauma) | | Anatomical location of injury | Radial side of wrist | Central or ulnar carpal region | | Associated swelling pattern | Lateral wrist swelling | Central or medial swelling | **Clinical Pearl:** In a patient with clinical signs of scaphoid fracture (snuffbox tenderness, pain on axial loading of thumb) but normal fracture line on plain films, disruption of the fat stripe supports the diagnosis and warrants advanced imaging (MRI or CT) or immobilization pending repeat radiographs in 10–14 days. ### Mechanism The scaphoid fat pad lies in the soft tissue lateral to the scaphoid. Fracture-associated haemorrhage and oedema displace this fat, obliterating the radiolucent stripe that is normally visible. **Tip:** Always look for the fat stripe sign on PA views when scaphoid fracture is clinically suspected but the fracture line is not clearly visible. 
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