Can retained foreign bodies in the foot cause peripheral nerve damage?

Can Retained Foreign Bodies in the Foot Cause Peripheral Nerve Damage?

Yes, retained foreign bodies in the foot can cause peripheral nerve damage through direct injury, compression, or secondary complications such as infection, inflammation, and granulomatous reactions.

Mechanisms of Nerve Damage

Retained foreign bodies in the foot pose multiple risks for peripheral nerve injury:

• Direct mechanical injury can occur at the time of penetration, with the foreign object directly transecting or contusing nerve structures 1, 2
• Chronic compression from the foreign body itself or from surrounding inflammatory tissue can lead to progressive nerve dysfunction 1, 2
• Secondary inflammatory response including granulomatous reactions develops around foreign bodies, creating mass effect and tissue edema that can compress adjacent nerves 1, 3
• Infectious complications such as cellulitis, abscess formation, myositis, and sinus tracts can develop and extend to involve neurovascular structures 1, 2

High-Risk Populations

Diabetic patients with peripheral neuropathy are at particularly elevated risk for both initial injury and delayed diagnosis:

• Diminished pain perception in diabetic neuropathy masks the initial penetrating injury, allowing foreign bodies to remain undetected 1
• Patients may continue to ambulate despite significant injury, driving the foreign body deeper into tissues 1
• Delayed presentation is common, with one case report documenting a diabetic patient presenting three weeks after injury with septic arthritis and osteomyelitis from a retained foreign body 4
• The combination of neuropathy and retained foreign bodies creates a "double hit" scenario where nerve damage may already exist, and additional injury compounds the deficit 1, 4

Clinical Presentation and Complications

Foreign bodies can present with delayed and atypical manifestations:

• Acute presentations include pain, swelling, erythema, and neurologic deficits at the injury site 1, 2
• Delayed presentations can occur months to years after initial injury, manifesting as expanding masses, chronic pain, or progressive neurologic symptoms 3, 5
• One case report documented a toothpick foreign body remaining quiescent for 31 months before presenting as an expanding painful mass 5
• Vascular and tendon injuries frequently accompany nerve damage, as these structures are anatomically adjacent in the foot 1, 2

Diagnostic Approach

The imaging strategy depends on whether the foreign body is radiopaque or radiolucent:

For Radiopaque Foreign Bodies (metal, glass, stone):

• Radiographs are the initial study of choice with approximately 98% sensitivity for radiopaque objects 1
• Multiple views should be obtained to maximize detection 2
• Imaging an unembedded fragment alongside the foot can help characterize morphology and density 1

For Radiolucent Foreign Bodies (wood, plastic, rubber):

• Ultrasound is the imaging modality of choice with 95% sensitivity for foreign body detection and 90% sensitivity specifically for wooden objects 1, 2
• Ultrasound can characterize the foreign body's relationship to nerves, tendons, vessels, and bone, which is critical for surgical planning 1, 2
• All foreign bodies appear hyperechoic with posterior acoustic shadowing on ultrasound 1, 2
• CT is 5-15 times more sensitive than radiography and can detect most foreign bodies including wood, which appears moderately hyperdense 1, 2
• MRI has lower sensitivity than CT and ultrasound for foreign body detection (58% sensitivity for foot foreign bodies) but excels at identifying complications such as edema, inflammation, abscess, and denervation changes 1, 2, 6

Critical Pitfalls to Avoid

• Never rely solely on radiographs for suspected radiolucent foreign bodies such as wood, plastic, or rubber, as these will not be visualized 1, 2
• Do not apply Ottawa ankle/foot rules in patients with peripheral neuropathy, as pain perception is diminished and these patients may ambulate despite significant injury 1
• Screen for metallic foreign bodies before MRI due to risks of heating and movement from the magnetic field 1
• Maintain high clinical suspicion even with negative initial imaging, particularly in diabetic patients who may have delayed or absent pain response 1, 4
• Recognize that deeper foreign bodies (>4 cm from skin) are more difficult to detect on ultrasound, and CT may be preferable in these cases 1

Management Implications

Early identification and removal are essential to prevent permanent nerve damage:

• Consultation with hand or foot surgeons is recommended due to the risk of iatrogenic damage to nerves, tendons, and vessels during removal 2
• Ultrasound can provide real-time guidance during surgical removal procedures 1, 2
• Even after removal, chronic pain, inflammation, and infection can persist if fragments remain 2, 7
• The time between injury and removal correlates with complication rates, with infections and granulomatous reactions more common in delayed presentations 3, 7, 5