Mechanism of Injury for Scaphoid Fracture
The typical mechanism of injury for a scaphoid fracture is a fall onto an outstretched hand (FOOSH), causing a hyperextension force on the wrist. 1, 2, 3
Primary Mechanism
- Scaphoid fractures most commonly result from hyperextension trauma to the wrist, typically when falling on an outstretched hand 1
- This mechanism creates a combination of forces that makes the scaphoid particularly vulnerable to fracture 3
- The fracture occurs when force is applied to the palmar aspect of the wrist while it is in extreme dorsiflexion 3
Population-Specific Considerations
- Scaphoid fractures show a bimodal distribution, affecting both younger (<18 years) and older (>65 years) populations 4
- In younger, more active patients, these fractures commonly occur during sports activities or vehicular accidents 4
- In older, less active patients, fractures typically result from falling onto an outstretched hand from ground level 4
Atypical Mechanisms
- While FOOSH is the classic mechanism, scaphoid fractures can occur with non-FOOSH hyperextension injuries 2
- Differential diagnoses should include scaphoid fracture with any hyperextension traumatic injury, even without the typical FOOSH mechanism 2
- Rare cases may involve multiple or secondary trauma, or loaded rotation forces, resulting in unusual fracture patterns such as segmental fractures 5
Clinical Pearls
- Scaphoid fractures represent approximately 11% of all upper extremity fractures 1
- The scaphoid is the most commonly fractured carpal bone, accounting for about 60% of wrist fractures 2
- Early detection can be challenging as initial radiographs may appear normal despite the presence of a fracture 2
- Clinical suspicion should remain high even in the absence of scaphoid tenderness when the mechanism involves wrist hyperextension 2
Diagnostic Approach
- Initial evaluation should include standard wrist radiographs with a dedicated "scaphoid view" 4, 6
- If initial radiographs are negative but clinical suspicion remains high, MRI without IV contrast is recommended as the next step 4, 6
- MRI without IV contrast offers the highest sensitivity (94.2%) and specificity (97.7%) for diagnosing scaphoid fractures 4, 6