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Difficulty: MediumInterpreting Imaging Results

A 23-year-old right-handed man comes to the urgent care clinic two hours after injuring his right wrist. He reports that he lost his balance while skateboarding and fell, bracing his impact with an outstretched hand and extended wrist. He complains of a deep, continuous ache on the radial aspect of his wrist. On physical examination, the overlying skin is intact and there is no visible gross deformity. He exhibits severe point tenderness in the anatomical depression located between the extensor pollicis longus and the extensor pollicis brevis tendons when his thumb is actively extended. Wrist range of motion is mildly limited secondary to pain. Posteroanterior, lateral, and specialized scaphoid views of the wrist on plain radiography are interpreted as showing no radiolucent lines, cortical step-offs, or malalignment. Based on the interpretation of these radiographic findings in the context of the patient's clinical presentation, which of the following is the most appropriate next step in management?

  1. Apply a thumb spica splint and arrange for follow-up clinical evaluation in two weeksAnswer
  2. B
    Discharge with a compression bandage and instructions to begin early range-of-motion exercises
  3. C
    Order an immediate non-contrast magnetic resonance imaging scan of the wrist
  4. D
    Obtain a nuclear medicine bone scintigraphy scan
  5. E
    Refer the patient to orthopedic surgery for urgent closed reduction and percutaneous pinning

Answer

The most appropriate next step is to apply a thumb spica splint and arrange for repeat clinical evaluation and imaging in 10 to 14 days.
The clinical scenario of a fall on an outstretched hand followed by anatomical snuffbox tenderness is the classic presentation of a scaphoid fracture. The critical concept in interpreting imaging for this injury is recognizing that initial plain radiographs are falsely negative in up to 30% of cases. Therefore, a normal X-ray does not rule out a fracture. Because the blood supply to the scaphoid enters distally and travels proximally, fractures risk disrupting perfusion to the proximal pole, leading to avascular necrosis and nonunion. To prevent these severe complications, any patient with clinical signs of a scaphoid fracture but negative initial imaging must undergo presumptive immobilization with a thumb spica splint. The patient is then re-evaluated with repeat radiographs in 10 to 14 days, at which point osteoclastic bone resorption at the fracture site usually renders the fracture line visible.

Step-by-Step Solution

1
Analyze the clinical presentation and physical examination findings.
The mechanism (fall on outstretched hand) and localized anatomical snuffbox tenderness strongly suggest a scaphoid fracture.
Snuffbox tenderness has a high sensitivity (over 90%) for scaphoid fractures.
2
Interpret the significance of the initial radiographic findings.
The plain radiographs are negative, but this does not reliably exclude a fracture.
Up to 30% of acute scaphoid fractures are radiographically occult on initial presentation due to lack of displacement or bony resorption.
3
Determine the appropriate management protocol based on the interpretation of a non-diagnostic imaging result.
The patient must be treated as having a presumed fracture with immobilization (thumb spica splint) and delayed repeat imaging.
This strategy prevents displacement and complications like avascular necrosis while waiting for bony resorption to make the fracture visible on subsequent radiographs.

Key Concept

Initial plain radiographs have a high false-negative rate for acute scaphoid fractures; patients with high clinical suspicion (snuffbox tenderness) must be presumptively immobilized and re-evaluated, regardless of a negative initial imaging result.
Estimated Time:1m 15s
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Interpreting Imaging Results

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