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 artificial 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 significant 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:
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 trephination: 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.
