Retained Foreign Body in the Hand or Foot — When Is Ultrasound Useful?

After a puncture, cut or stepping on a sharp object, ultrasound can help locate retained glass, wood, metal or plastic in the hand or foot—especially when the fragment is not visible on an X-ray. A normal ultrasound does not exclude every retained foreign body, and the decision to remove a fragment depends on its material, depth, symptoms and proximity to nerves, vessels, tendons or a joint.

When should a retained foreign body be suspected?

Common examples include a splinter, thorn, piece of glass, metal or plastic after an injury to the hand or foot. Suspicion is higher when the patient remembers the object entering the skin, the wound was deep, or part of the object broke during an attempt to remove it.

Possible clues include focal tenderness, a sharp sensation during movement or weight bearing, a palpable lump, recurrent redness, drainage from the wound or difficulty fully bending a finger. Symptoms may develop only after several days or weeks. Pain alone, however, does not prove that a foreign body remains: a haematoma, tendon or nerve injury, fracture and infection can produce similar symptoms.

X-ray or ultrasound—which is more useful?

X-rays show some materials well

Plain radiographs are usually the first test when glass, metal or another radiopaque material is possible. They can also reveal a fracture. Wood, thorns and some plastics are much less visible. A very small fragment, or one projected over bone, may also be difficult to identify.

Ultrasound shows soft tissues and anatomical relationships

Ultrasound can show the foreign body itself and the tissue reaction around it. It can help determine the fragment’s depth and its relationship to a tendon, tendon sheath, nerve, blood vessel or joint. For superficial foreign bodies, the skin can be marked before a procedure and, in selected cases, removal can be guided in real time.

Ultrasound also has limitations. Detection depends on the fragment’s size, material and location, the time since injury and the examiner’s experience. Air in a fresh wound, proximity to bone and deep location can make assessment more difficult. In a meta-analysis of 17 studies, pooled ultrasound sensitivity was 72% and specificity 92%. A positive result can therefore be very helpful, but a normal result does not completely exclude a retained foreign body when clinical suspicion remains high.

When are CT or MRI needed?

CT may be useful for deeply located foreign bodies, complex anatomy or an equivocal radiograph. MRI is used selectively, particularly when soft-tissue complications need to be assessed. If a metallic fragment is possible, MRI should not be ordered blindly; the type and location of the material should first be established.

Does every foreign body need to be removed?

No. Removal is more often indicated when the fragment causes pain, infection, restricted movement or compression of a nerve, vessel or tendon. Organic material such as wood or a thorn is more likely to provoke inflammation and infection. Foreign bodies close to a joint, tendon sheath or neurovascular structures deserve prompt assessment.

A small, deeply located, inert and asymptomatic fragment can sometimes be left in place when retrieval would cause more tissue damage than benefit. The decision should balance the expected benefit of removal against the procedural risk. Tetanus protection should also be reviewed according to the wound and vaccination history.

What does ultrasound-guided removal involve?

The fragment is first located and the safest access route is planned. In an appropriate superficial location, a small incision can be made and the instrument followed under real-time ultrasound, potentially reducing unnecessary tissue dissection. Not every case is suitable for this approach.

Operating-room conditions may be required when the object is deep, brittle, large, fragmented, close to a nerve or vessel, has penetrated a tendon, or lies within a joint. Blind attempts to dig out an unseen fragment with a needle or tweezers can push it deeper, break it into smaller pieces and increase the risk of infection.

What should you do after a fresh injury?

• Do not probe a deep wound with household instruments.
• If an object remains deeply embedded, do not force it out.
• Cover the wound with a clean dressing and reduce loading of the painful hand or foot.
• Note what material caused the injury and when it occurred.
• For a deep, contaminated or puncture wound, seek advice about cleaning, antibiotics when indicated and tetanus prophylaxis.

Warning signs

Urgent assessment is needed for increasing pain and swelling, rapidly spreading redness, pus, fever, red streaking along the limb, numbness or weakness of finger or toe movement, a pale or cold hand or foot, severe pain when moving a finger, or a wound that may have penetrated a joint. A high-pressure injection injury requires immediate medical attention even when the skin opening looks minor.

Key points for an orthopaedic surgeon

Ultrasound is especially valuable when a retained fragment is not visible on X-ray or when its relationship to soft tissues needs to be mapped. It is not a perfect test. When the history and symptoms still strongly suggest a retained foreign body, one normal imaging result should not automatically end the diagnostic process.

Sources

1. Davis J, et al. Diagnostic Accuracy of Ultrasonography in Retained Soft Tissue Foreign Bodies: A Systematic Review and Meta-analysis. Acad Emerg Med. 2015;22(7):777–787. DOI: 10.1111/acem.12714. PubMed.
2. Rupert J, Honeycutt JD, Odom MR. Foreign Bodies in the Skin: Evaluation and Management. Am Fam Physician. 2020;101(12):740–747. Full text.

Polish version · Diagnostic Tests · For Patients

Content prepared by: Tomasz Poboży - orthopaedic surgeon.