What is the best imaging modality to detect glass in the foot?

Imaging for Glass Foreign Body in the Foot

Start with plain radiographs of the foot in multiple views—glass is radiopaque and detectable on X-ray in the vast majority of cases, making it the appropriate first-line imaging modality. 1

Initial Imaging Approach

• Plain radiographs should be obtained first for any suspected glass foreign body in the foot, as glass is radiodense and can be detected on X-rays unlike truly radiolucent materials such as wood, plastic, and rubber 2
• Glass appears radiopaque on radiography with approximately 98% sensitivity for detecting glass foreign bodies in soft tissue 3
• Studies demonstrate that 25 out of 26 patients (96%) with glass foreign bodies had them successfully detected radiographically 4
• All types of glass—both leaded and non-leaded—are sufficiently radiopaque to be visualized on standard radiographs 3, 5

When Radiographs Are Negative

If radiographs are negative but clinical suspicion remains high, ultrasound is the next appropriate imaging modality for superficial foreign bodies in the foot 1

• Ultrasound is specifically recommended by the American College of Radiology as "usually appropriate" for detecting foreign bodies when radiographs are negative in penetrating foot trauma 1
• Ultrasound shows 90% sensitivity for visualizing foreign bodies and displays all foreign bodies as hyperechoic with posterior acoustic shadowing 1, 2
• Ultrasound provides real-time guidance for removal and precise localization of depth from the surface 2, 6

Alternative Advanced Imaging

CT should be reserved for cases where ultrasound is unavailable, equivocal, or when precise anatomic localization is needed 1

• CT demonstrates 63% sensitivity and 98% specificity for detecting various foreign bodies including glass 1
• CT is 5-15 times more sensitive than radiography for foreign body detection 2
• Glass appears moderately hyperdense on CT (at least 2000 Hounsfield units), making it readily distinguishable from soft tissue 2
• CT provides superior information about surrounding inflammatory reactions, adjacent tendons, neurovascular bundles, and potential complications 7

Critical Pitfalls to Avoid

• Small glass fragments may be missed on X-ray, especially if obscured by adjacent osseous structures—do not rely solely on negative radiographs to exclude glass 3, 2
• Never limit examination to inspection and probing alone—in one series, 9 out of 26 patients had glass foreign bodies overlooked on previous visits where radiographic examination was not performed 4
• Retained glass can trigger granulomatous reactions and subsequent soft tissue infections including cellulitis, abscess formation, or sinus tracts 2
• If clinical suspicion persists despite negative imaging, consider an additional imaging modality rather than dismissing the concern 1

Practical Algorithm

1. Obtain plain radiographs first (multiple views including AP, lateral, and oblique) 2, 8
2. If X-ray is positive, proceed with removal using radiographic guidance for localization 4
3. If X-ray is negative but clinical suspicion remains high, obtain ultrasound immediately 1, 2
4. If ultrasound is unavailable or equivocal, consider CT for precise localization relative to critical structures before removal 2, 8, 7