10.07 Subungual Hematoma
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agk's Library of Common Simple Emergencies

Presentation
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After a blow or crushing injury to the 
fingernail, the patient experiences severe and 
sometimes excruciating pain, that persists for 
hours, and may even be associated with a 
vaso-vagal response. The fingernail has an 
underlying deep blue-black discoloration which 
may be localized to the proximal portion of the 
nail or extend beneath its entire surface.

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

- X ray the finger to rule out an underlying 
    fracture of the distal phalanx and test for 
    a possible [avulsion of the extensor 
    tendon].
- Paint the nail with 10% povidone iodine 
    (Betadine) solution.
- Adhere to universal blood and bodily-fluid 
    precautions (blood is under pressure and 
    may spurt out).
- Perform a trephination at the base of the 
    nail, using the free end of a hot paper 
    clip, electric cauterizing lance or drill. 
    When performed quickly, patients do not 
    feel the heat, just relief from pain. Tap 
    rapidly with the cautery or drill a few 
    times in the same spot at the base of the 
    hematoma until the hole is through the 
    nail. When resistance from the nail gives 
    way, stop further downward pressure to 
    avoid damaging the nail bed.
- Persistant bleeding from this opening can be 
    controlled by having the patient hold a 
    folded 4" x 4" gauze pad firmly over the 
    trephination while holding his hands over 
    his head.
- Apply an antibacterial ointment such as 
    Betadine and cover the trephination with a 
    Band-Aid.
- To prevent infection, instruct the patient to 
    keep his finger dry for 2 days and not to 
    soak it (e.g., go swimming) for 1 week.
- If there is an underlying fracture, instruct 
    the patient to keep his finger as dry as 
    possible for the next ten days and return 
    immediately at the first sign of infection.
- A protective aluminum finger tip splint may 
    also be comforting, especially if the bone 
    is fractured.
- Inform the patient that he will eventually 
    lose his fingernail, until a new nail grows 
    out after two to six months.

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

- Do not perform a trephination on a subungual 
    ecchymosis (see below).
- Do not perform a trephination using a hot 
    cautery device on a patient wearing artif- 
    icial acrylic nails, which are flammable.
- Do not perform a trephination when there is 
    an underlying fracture (this theoretically 
    converts a closed fracture to an open one) 
    unless there is sufficient pain to justify 
    it. The patient should also understand the 
    potential risk of developing osteomyelitis, 
    as well as the need for keeping the finger 
    dry.
- Do not perform a digital block. Anesthesia 
    should not be necessary for a simple nail 
    trephination of an uncomplicated subungual 
    hematoma.
- Do not perform a trephination on a patient 
    who is no longer experiencing any signif- 
    icant pain at rest. A mild analgesic and 
    protective splint will usually suffice.
- Do not make such a small opening that free 
    drainage does not occur. The electrocautery 
    tip may have to be bent to the side, 
    widened, or moved around to make a wide 
    enough hole.
- Do not hold a hot paper clip or cautery wire 
    on the surface without applying enough 
    slight pressure to melt through the nail. 
    Just holding the hot tip adjacent to the 
    nail can heat up the hematoma and increase 
    the pain without making a hole to relieve 
    it.
- Do not send a patient home to soak his finger 
    after a trephination. This will break down 
    the protective fibrin clot and introduce 
    bacteria into this previously sterile 
    space.
- Do not routinely prescribe antibiotics. Even 
    when opening a subungual hematoma with an 
    underlying fracture of the distal phalynx, 
    antibiotics have not been shown to be of 
    any value in preventing infection.
- Do not remove the nail even with a large 
    subungual hematoma. It is not necessary to 
    inspect for nailbed lacerations or repair 
    them with a closed injury.

Discussion:
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The subungual hematoma is a space-occupying 
mass that produces pain secondary to increased 
pressure against the very sensitive nailbed and 
matrix. Given time, the tissues surrounding 
this collection of blood will stretch and 
deform until the pressure within this mass 
equilibrates. Within 24 hours the pain 
therefore subsides and, although the patient 
may continue to complain of pain with activity, 
performing a trephination at this time may not 
improve his discomfort to any significant 
extent and will expose the patient to the risk 
of infection. If you choose not to perform a 
trephination explain this to the patient who 
may be expecting to have his nail drained. 
There is some risk of missing a nail bed 
laceration under the hematoma, but, for most 
underlying lacerations, splinting by its own 
nail may be superior to suturing. When there 
are associated lacerations, open hemorrhage or 
broken nails, a digital block should probably 
be performed and the nail lifted up for 
inspection of the nailbed and repair of any 
[lacerations]. Keep in mind that not all dark 
patches under the nail are subungual hematomas. 
Consider the diagnosis of melanoma, Kaposi's 
sarcoma and other tumors when the history of 
trauma and the physical examination are not 
consistent with a simple subungual hematoma.

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

- Seaberg DC, Angelos WJ, Paris PM: Treatment 
    of subungual hematomas with nail trephin- 
    ation: a prospective study. *Am J Emerg 
    Med* 1991;9:209-210.
- Simon RR, Wolgin M: Subungual hematoma: 
    association with occult laceration 
    requiring repair. *Am J Emerg Med* 
    1987;5:302-304.

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