Management of Metal Foreign Bodies in Soft Tissue
The recommended management approach for metal foreign bodies in soft tissue begins with radiographic imaging followed by ultrasound-guided removal as the first-line treatment procedure for accessible objects, while surgical exploration is necessary for foreign bodies adjacent to critical structures or embedded in bone. 1
Diagnostic Approach
Initial Imaging
- Radiographs of the area of interest are the appropriate first imaging study for suspected metal foreign bodies, with multiple views to maximize detection of these radiopaque objects 2
- Metal foreign bodies are radiodense and can be detected on radiographs, unlike plastic, rubber, and wood which are radiolucent 2
Secondary Imaging
- If radiographs are negative but a foreign body is still suspected, ultrasound (US) is the preferred imaging modality with a reported sensitivity of 95% for foreign body detection 2
- CT without IV contrast is an equivalent alternative to US, with 5-15 times higher sensitivity than radiography for detecting foreign bodies 2
- CT can precisely localize foreign bodies and identify their composition based on attenuation and Hounsfield unit values 2
- MRI should be avoided initially for metallic foreign bodies due to potential risks from the magnetic field and should only be used after radiographic screening confirms safety 2
Removal Techniques
Ultrasound-Guided Removal
- US-guided removal is highly effective and should be considered as a first-line treatment procedure for accessible metal foreign bodies 3
- US can characterize foreign body morphology, depth, and relationship to adjacent structures, and provide real-time guidance during removal 2, 1
- The procedure involves making a small incision in the skin just wide enough for the foreign body to pass through, then inserting surgical forceps under US guidance to remove it 4, 3
- This technique has shown success rates approaching 100% with minimal complications 4, 3
Fluoroscopic Guidance
- Percutaneous fluoroscopically guided removal (PFGR) is another effective technique for metallic foreign bodies with reported success rates of 94% 5
- For superficial metal foreign bodies, direct removal with curved forceps under real-time fluoroscopy can be performed 5
- For deeper objects, trocar technique using instruments for percutaneous procedures may be necessary 5
CT-Guided Removal
- 3D CT-guided technique can be used for small metal foreign bodies that are difficult to localize 6
- This approach involves placing needle finders around the foreign body under CT guidance, then dissecting along the path of the closest needle to remove the object 6
- This method has shown to be accurate and reliable for small metal foreign bodies 6
Surgical Exploration
- Surgical exploration is necessary when the foreign body is adjacent to critical structures or embedded in bone 1
- Hand surgeons or appropriate specialists should be consulted due to the risk of damage to tendons, nerves, and blood vessels during removal 1
- Minimally invasive approaches such as laparoscopy with navigation systems can be considered for foreign bodies in deep anatomical locations 7
Complications and Follow-up
- Potential complications include tendon or nerve injury from the foreign body or during removal, and chronic inflammation and infection 1
- Antibiotic prophylaxis should be considered after removal to prevent infection 4
- Follow-up imaging may be necessary to confirm complete removal, especially if multiple foreign bodies were present 2
Special Considerations
- For metal foreign bodies in the hand, special attention must be paid to the complex anatomy and potential for functional impairment 1
- MRI is contraindicated before confirming the absence of ferromagnetic properties due to potential for severe soft tissue heating and motion of the foreign body 2
- The depth of the foreign body influences the choice of removal technique, with objects deeper than 4cm from the skin being more difficult to detect and remove with ultrasound 2