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.
CT Scan may be more sensitive than plain-film x-ray, but they also cost more and have an increased radiation dose.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.
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.
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