What is the likely diagnosis and management for a 15-year-old boy with wrist pain near the thumb, tenderness to palpation of the snuffbox, and pain on active range of motion of the thumb after a fall onto an outstretched hand, with a normal X-ray?

Suspected Scaphoid Fracture in a 15-Year-Old with Anatomical Snuffbox Tenderness

The most likely diagnosis is a scaphoid fracture, and despite the normal X-ray, the patient should be treated with thumb spica immobilization and follow-up imaging (preferably MRI) within 1-2 weeks to confirm the diagnosis.

Diagnosis

The clinical presentation strongly suggests a scaphoid fracture:

• Fall onto an outstretched hand (classic mechanism)
• Tenderness in the anatomical snuffbox
• Pain with active range of motion of the thumb
• Normal initial X-ray (up to 30% of scaphoid fractures are radiographically occult initially) 1

Key Physical Examination Findings

• Anatomical snuffbox tenderness (100% sensitive for scaphoid fracture) 2
• Pain on thumb movement (positive predictive finding)
• Tenderness over the scaphoid tubercle (another sensitive finding)

Management Algorithm

1. Initial Management:

   • Immobilize in a thumb spica splint or cast immediately 3
   • This is necessary even with normal X-rays due to high suspicion for scaphoid fracture

2. Imaging Approach:

   • Initial X-rays are normal but insufficient to rule out scaphoid fracture 4
   • MRI is the preferred follow-up imaging test for suspected scaphoid fractures not visible on initial X-rays 3, 4
   • If MRI is unavailable (as in this case), options include:
     • Repeat X-rays in 10-14 days (may show sclerosis at fracture line) 1
     • CT scan (good for ruling in fractures but inadequate for ruling out) 4

3. Clinical Decision Making:

   • Using the Clinical Scaphoid Score (CSS):
     • Anatomical snuffbox tenderness in ulnar deviation (3 points)
     • Tenderness over scaphoid tubercle (2 points)
     • Pain upon longitudinal compression of thumb (1 point)
   • A CSS score ≥4 warrants advanced imaging (MRI) 5
   • This patient likely has a score of at least 4 based on the examination findings

Important Considerations

• Scaphoid fractures are the most common carpal fracture (70% of all carpal bone fractures) 4
• Untreated scaphoid fractures can lead to nonunion, avascular necrosis, and long-term wrist dysfunction
• The absence of snuffbox tenderness is the only reliable physical finding to rule out scaphoid fracture (LR- = 0.15) 4
• Combining clinical signs (snuffbox tenderness, scaphoid tubercle tenderness, and pain on longitudinal compression) improves diagnostic accuracy 2

Common Pitfalls to Avoid

1. Do not rely solely on initial X-rays - they miss up to 30% of scaphoid fractures 1
2. Do not delay immobilization - even suspected scaphoid fractures should be immobilized pending definitive diagnosis
3. Do not dismiss persistent symptoms - if pain continues despite normal initial imaging, further investigation is required
4. Do not forget alternative diagnoses - MRI and CT can identify other causes of radial-sided wrist pain if scaphoid fracture is ruled out 3

In adolescents like this patient, growth plate injuries should also be considered, but the clinical presentation is most consistent with scaphoid fracture.