What is the best initial imaging study for an adult patient with suspected glass in their arm after a car accident?

Imaging for Suspected Glass Foreign Body in Arm After Car Accident

Order plain radiographs (X-rays) of the affected arm immediately—glass is radiopaque and visible on standard X-rays in the vast majority of cases. 1, 2

Initial Imaging Approach

Plain radiographs are the first-line imaging study for suspected glass foreign bodies in the arm following trauma. 1, 2 The American College of Radiology specifically recommends obtaining radiographs immediately for any patient with a puncture wound or suspected glass foreign body, as glass is radiodense and detectable on X-rays in nearly all cases. 2

Why Radiographs Work for Glass

• Glass fragments are radiopaque regardless of whether they are leaded or non-leaded, making them visible on standard radiography with approximately 98% sensitivity. 1
• All modern glass types used in car windows and other automotive glass are detectable radiographically. 3
• Even minute glass splinters can be visualized with proper radiographic technique and careful scrutiny. 4
• Research from motor vehicle accident injuries specifically confirms that glass from car windows is readily detected on plain films. 5

Technical Considerations

• Obtain at least two orthogonal views (perpendicular to each other) to accurately localize the fragment in three-dimensional space. 1
• If an unembedded glass fragment is available from the accident scene, imaging it alongside the arm can provide additional information about the morphology and density of the retained foreign body. 1
• High-resolution or mammographic techniques may be needed for very small splinters, though standard radiography is usually sufficient. 4

When Radiographs Are Negative But Clinical Suspicion Remains High

If initial radiographs are negative but you strongly suspect a retained glass fragment based on mechanism of injury or physical examination findings:

Ultrasound as Second-Line Imaging

Ultrasound is the appropriate next imaging study when radiographs are negative. 1 While ultrasound is primarily recommended for radiolucent foreign bodies (wood, plastic), it serves several important roles when radiographs fail to detect glass:

• Ultrasound can localize glass fragments that were missed on radiographs due to very small size or obscuration by adjacent bone. 2
• It allows assessment of surrounding soft tissues for fluid collections, abscess formation, or developing infection around retained fragments. 2
• Ultrasound enables real-time guidance for foreign body removal. 1

CT for Complex Cases

CT without IV contrast may be appropriate if: 1

• Precise localization is needed for surgical planning
• The fragment is suspected to be deep within tissues or near bone
• Multiple fragments are suspected from high-energy trauma

However, CT has only 63% sensitivity for foreign body detection (though 98% specificity), making it less reliable than radiographs for initial glass detection. 1

Common Pitfalls to Avoid

• Never skip radiographs in favor of ultrasound for glass injuries—this reverses the appropriate imaging hierarchy and will miss most glass foreign bodies. 2
• Do not rely on clinical examination alone—studies show that glass foreign bodies are frequently missed on initial clinical evaluation, with approximately half being overlooked when radiographs are not obtained. 5, 4
• Avoid inadequate radiographic views—single-view radiographs miss a significant percentage of foreign bodies; always obtain orthogonal projections. 1
• Do not assume superficial wounds don't need imaging—while very superficial, adequately explorable wounds have low rates of missed foreign bodies (1.5%), deeper wounds have much higher miss rates (7.7%) without radiographic confirmation. 6

Clinical Context for Car Accident Injuries

Given the mechanism of injury (car accident), consider that:

• Motor vehicle crashes cause glass injuries from broken windows in 42% of hand glass foreign body cases, making this a high-risk mechanism. 5
• Car accident victims may have polytrauma requiring broader imaging assessment beyond the isolated arm injury. 1
• Document neurovascular status before and after any intervention, as vascular or nerve injury may accompany penetrating glass trauma. 7

Consequences of Missed Glass Foreign Bodies

Retained glass fragments can cause: 5

• Infection and delayed wound healing
• Persistent pain
• Late injury from fragment migration through tissues
• Chronic inflammation

These complications justify the low cost and high yield of obtaining radiographs in all suspected cases.