Imaging for Suspected Splinter
Ultrasound is the best initial imaging modality for suspected soft tissue splinters, with a sensitivity of 94.5% and the ability to detect radiolucent wooden foreign bodies that are invisible on plain radiographs. 1, 2
Why Ultrasound is Preferred
- High sensitivity for all splinter types: Ultrasound reliably detects wooden splinters, thorns, plastic, metal, and glass fragments in soft tissue 1, 3, 2
- Superior for radiolucent materials: Wood and organic materials (the most common retained foreign bodies) are radiolucent on X-rays but highly visible on ultrasound 1, 4
- Provides precise localization: Ultrasound accurately measures depth from the skin surface and length of the foreign body, which surgeons find extremely useful for planning removal 4, 2
- No radiation exposure: This is particularly important for extremity injuries where repeated imaging may be needed 1
- Real-time guidance: Can be used intraoperatively to guide removal, minimizing surgical dissection and operating time 4
Technical Approach
- Use high-resolution transducer: A 7.5 MHz or higher frequency linear probe is essential for optimal visualization 2
- Scan in two planes: Both axial and sagittal planes should be examined to fully characterize the foreign body 1, 2
- Document key features: Record the nature, length, depth from surface, and relationship to adjacent structures 2
When Ultrasound May Be Limited
- Very small splinters near bone: Splinters <4mm in width located immediately adjacent to bone may be difficult to detect with ultrasound, and CT or MRI may be more sensitive in this specific scenario 1
- **Acute injuries (<3 days)**: Fresh wooden splinters near bone are harder to visualize; those soaked longer (>5 months) become easier to detect with either ultrasound or MRI 1
Alternative Imaging Modalities
- MRI: Nearly equivalent to ultrasound for chronic wooden foreign bodies (>5 months), with better sensitivity perpendicular to the splinter's long axis, but less practical and more expensive 1
- Plain radiographs: Only useful for radiopaque materials (metal, glass); will miss most wooden splinters and thorns 4, 3
- CT: Not routinely indicated; may help for small splinters very close to bone when ultrasound is equivocal, but involves radiation exposure 1
Clinical Pitfall to Avoid
Do not rely on plain radiographs alone when clinical suspicion for a wooden splinter is high—wood fragments and thorns are radiolucent and will be missed, leading to delayed diagnosis, infection risk, and unnecessary surgical exploration 4, 3. Proceed directly to ultrasound evaluation when the history suggests a retained organic foreign body.