11.08 Subcutaneous foreign body
===============================

agk's Library of Common Simple Emergencies

Presentation
------------

Small, moderate-velocity metal fragments can be 
released when a hammer strikes a second piece of 
metal, such as a chisel. The patient has noticed 
a stinging sensation and a small puncture wound 
or bleeding site, and is worried that there might 
be something inside. BB shot will produce a more 
obvious but very similar problem. Another 
mechanism for producing radio-opaque foreign 
bodies includes punctures with glass shards, 
especially by stepping on glass fragments or 
receiving them in a motor vehicle accident. 
Physical findings will show a puncture wound and 
may show an underlying, sometimes palpable, 
foreign body.

What to do:
-----------

- Be suspicious of a retained foreign body in all 
    wounds produced by a high velocity missle or 
    sharp fragile object. The most common error 
    in the management of soft tissue foreign 
    bodies is failure to detect their presence.
- X ray the wound to document the presence and 
    location of the suspected foreign body. 
    Explain how difficult it often is to remove a 
    small metal fleck, and that often these are 
    left in without any problem (like shrapnel 
    injuries).
- Inform the patient that, since it is best to 
    remove the foreign body, you will attempt a 
    simple technique, but that in order to avoid 
    more damage, you will not extend your search 
    beyond 15-30 minutes.
- If the foreign body is in an extremity, then it 
    is preferable, and sometimes essential, to 
    establish a bloodless field.
- Anesthetize the area with a small infiltration 
    of l% Xylocaine with epinephrine (avoid 
    tissue swelling, and do not use epinephrine 
    on digits).
- Take a blunt stiff metal probe (not a needle) 
    and gently slide it down the apparent track 
    of the puncture wound. Move the probe back 
    and forth, fanning it in all directions, 
    until a clicking contact between the probe 
    and the foreign body can be felt and heard. 
    This should be repeated several times until 
    it is certain that contact is being made with 
    the foreign body.
- After contact is made, fix the probe in place 
    by resting the hand holding the probe against 
    a firm surface and then, with your other 
    hand, cut down along the probe with a #15 
    scalpel blade until you reach the foreign 
    body. Do not remove the probe.
- Reach into the incision with a pair of forceps 
    and remove the foreign body (located at the 
    end of the probe).
- Close the wound with strip closures or sutures.
- If the track is relatively long and the foreign 
    body is very superficial and easily palpable 
    beneath the skin, then it may be advantageous 
    to eliminate the probe and just cut down 
    directly over the foreign body.
- Provide tetanus prophylaxis.
- Warn the patient about signs of developing 
    infection.
- If you are unable to locate the foreign body in 
    15-30 minutes, inform the patient that in the 
    case of a small metal fleck, the wound will 
    probably heal without any problem. It may 
    migrate to the skin surface over a period of 
    months or years, at which time it can be more 
    easily removed. Should the wound become 
    infected, it can be successfully treated with 
    an antibiotic, and the foreign body can be 
    more easily removed if a small abscess forms. 
    Patients with glass, sea shell fragments, 
    gravel or other potentially harmful objects 
    imbedded subcutaneously should have them 
    removed as soon as possible, and will require 
    surgical consultation or referral.
- Always provide the patient with a physician who 
    can perform the necessary followup care.
- Schedule a wound check within 48 hours or warn 
    the patient about signs of infection.

What not to do:
---------------

- Do not cut down on the metal probe if there is 
    any possibility of cutting across a 
    neurovascular bundle, tendon or other 
    important structure.
- Do not attempt to cut down to the foreign body, 
    unless it is very superficial, without a 
    probe in place and in contact with the 
    foreign body.

Discussion
----------

Moderate-velocity, metallic foreign bodies rarely 
travel deeply into the subcutaneous tissue, but 
you must consider a potentially serious injury 
when these objects strike the eye. A specialized 
orbital CT scan should be obtained in these 
cases. 

With simple penetration, x rays are needed to 
document the presence of a foreign body and its 
location relative to significant anatomic 
structures. X rays are usually of little value, 
though, in accurately locating metalic flecks. 
Even when skin markers are used, because of 
variances in the angle of the x ray beam to the 
film, relative to the skin marker and foreign 
body, the apparent location of the foreign body 
is often significantly different from the real 
location. An incision made over the apparent 
location, therefore, usually produces no foreign 
body. Needle localization under fluroscopy may be 
required for those objects that must be removed 
and the simple probe technique described above 
fails to deliver the foreign body. 

If you are attempting to remove a metallic object 
and you have a strong eye magnet available, it 
can be substituted for the probe described above. 
First, enlarge the entrance wound and then, after 
contact with the magnet, the object can be 
dissected out or even pulled out with the magnet. 

Almost all glass is visible on plain x rays, but 
small fragments, between 0.5 and 2.0mm, may not 
be visible, even when left and right oblique 
projections are added to the standard 
posterior-anteroir and lateral views. Any patient 
who complains of a foreign body sensation should 
be assumed to have one even in the face of 
negative x rays.

References:
-----------

- Courter BJ: Radiographic screening for glass 
    foreign bodies--what does a "negative" 
    foreign body series really mean? *Ann Emerg 
    Med* 1990;19:997-1000.
- Schlager D, Sanders AB, Wiggins D, et al: 
    Ultrasound for the detection of foreign 
    bodies. *Ann Emerg Med* 1991;20:189-191.
- Ginsburg MJ, Ellis GL, Flom LL: Detection of 
    soft-tissue foreign bodies by plain 
    radiography, xerography, computed tomography 
    and ultrasonography. *Ann Emerg Med* 
    1990;19:701-703.
- Montano JB, Steele MT, Watson WA: Foreign body 
    retention in glass-caused wounds. *Ann Emerg 
    Med* 1992;21:1360-1363.

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