Felons, those acute bacterial infections of distal digits, may develop in a finger or toe, rapidly swelling and developing redness and intense, throbbing pain. The redness and swelling are caused by lymphangitis and cellulitis. The earlier it is in the course of a felon, the less likely it is that an abscess has had time to form in the pulp of the digit.
A felon may originate as a paronychia, hyponychia, subungual abscess, or an eponychia. A subungual abscess may be occult—the pus under the nail is undetectable when looking through the nail at the nail bed—or it may be visible. The classic felon presents with no accompanying paronychia, hyponychia, eponychia, or visible pus under the nail, and usually originates as an occult subungual abscess, not in the pulp, as dogma maintains.
I believe occult subungual abscesses have escaped the notice of science for two reasons: The visible subungual abscess gives rise to an expectation that all subungual abscesses are visible and because of the belief that a felon begins in the pulp of a digit. This notion has discouraged consideration of the possibility that a felon could originate anywhere but the pulp. When pus is found under the nail in association with a felon, the assumption, incorrect though it is, has been that the subungual abscess is secondary to the pulp infection.
There has never been a satisfactory explanation of how bacteria get into the pulp to cause a felon. The only hypothesis offered is that a wound such as a prick introduces bacteria into the pulp. The problem with this hypothesis is that there is never any notice of the prick or wound or of the initial pain or subsequent soreness caused by a prick or wound. And there is never any physical evidence of injury to the skin.
It is time to abandon this magical wound hypothesis.
Because of paronychia, eponychia, hyponychia, and visible subungual abscess, we know the junction of the nail and its skin attachments are predisposed to infection, and we should now recognize that a felon is another manifestation of that same predisposition.
Felons require drainage of the nail bed, so I recommend gently removing the nail. Ultrasound can detect abscess in the pulp, and drain it if present. Consider an x-ray to look for osteomyelitis and to establish that it is not present. The longer the infection is present, the greater the risk is of tissue destruction and other complications.
Refer to a hand specialist if the felon has advanced beyond a felon with pulp abscess. Also check tetanus vaccination status, and use antibiotics as appropriate. It is possible that early felons treated with exposure and drainage may not require antibiotics, but that has not been determined. Follow up in one to three days and as needed.
An anatomical error in the felon literature also has to be addressed. Allen Kanavel, MD, made it clear in his book Infections of the Hand, first published in 1912, that only one compartment exists in the volar distal digit. He used the word septa, however, to name the fibers that extend from the periosteum out to the pulp. Because septa can mean wall as well as fiber, I suspect someone misunderstood Dr. Kanavel and assumed that septa meant walls and that the walls created compartments.
That misunderstanding was inserted into the surgical literature in the first half of the 20th century. A review of the histology of the human finger is all that is needed to ascertain that the walls and compartments do not exist.
The erroneous belief in walls and compartments may have some practical importance. When a pulp incision does not yield pus, an attempt may be made to cut through as many fictitious walls as possible to find pus believed to be localized within a compartment. An injury caused by an unnecessary incision is made worse by unnecessary dissection of the fingertip.
Dr. Rupertis a retired board-certified emergency physician in Clinton, MD.Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.