I recently read a nice review article on the topic: Diagnosis and Management of Foreign Bodies in the Skin. Most humans at one time or another will have an experience with a foreign body – splinters, thorns, broken glass, etc.
Physicians see the worst ones. The ones that aren’t easily removed or only partially removed.
The history of the injury is always the starting place. It is important to know when (recent, days or weeks ago), where (home, farmyard, ocean, etc), how (sharp object, fist to mouth, blunt object), and if known the possible foreign body (splinter, fish spine, teeth, glass).
Remember fragments of the foreign body can be left in the wound even if you or the patient think it was removed. Check to make sure the “needle” is complete, etc.
It is also important to remember with blunt penetration other materials may be embedded along with the offending agent.
If a nail penetrates both the shoe and the sock, it may also force leather, rubber, or sock material into the foot. A blunt object may push a plug of epidermis deep into the dermis. This traumatic implantation results in an epidermal inclusion cyst.
When assessing the patient remember 4 P's: pain, pulselessness, paresthesia, and pallor.
Pain to palpation over an embedded foreign body can help you locate it, especially when located under the skin but above the muscle layer as is the focus of this article.
Pulselessness and pallor can indicate a vascular injury. Paresthesia can indicate a nerve injury.
The article has a nice section on radiologic evaluation of foreign bodies under the skin which can be very important in localization of the object. Especially important when it’s an old injury with healed skin (visualization impossible), infected wound (patient won’t allow adequate palpation exam), foreign body deeper than 5 mm, etc.
Diagnostic tests used to determine the location of a foreign body in the skin, include x-ray, computed tomography (CT) scan, ultrasonography, and magnetic resonance imaging (MRI).
X-ray -- A plain film should be ordered first if a suspected foreign body is not visible to the eye during the initial exam.
Metal, aluminum, bone, some types of fish spines, teeth, graphite (from pencils), some types of plastics, glass, gravel, stone, wood, and sand are visible on plain x-ray.
Multiple projections can also be used to help estimate the location of the foreign body after placement of radiopaque skin markers, such as paper clips, on the skin at the wound site.
CT Scan may be more sensitive than plain-film x-ray, but they also cost more and have an increased radiation dose.
Ultrasonography is a great tool to use to locate foreign bodies made of wood, plastic, and radiolucent materials that are larger than 4 to 5 mm.
Ultrasonography has a sensitivity of 50% to 90% and may be used to estimate the depth and size of a foreign body, as well as determine its relationship to surrounding anatomic structures.
Magnetic Resonance Imaging should not be used on foreign bodies suspected to be gravel or metal-containing. As with CT scans, this choice can be more expensive and has a higher radiation dose than plain x-rays.
One of, if not the most important thing, to remember in removing foreign bodies is to inspect the removed object and try to assess whether is has been removed entirely rather than leaving part of it.
Otherwise, it’s good basic wound care – clean, irrigate, closure, tetanus status, antibiotics or not, etc.
Diagnosis and Management of Foreign Bodies in the Skin; Winland-Brown, Jill E., Allen, Sandra; Advances in Skin & Wound Care. 23(10):471-476, October 2010; doi: 10.1097/01.ASW.0000383220.72147.e2