A felon is a subcutaneous infection or abscess in the pulp space on the volar surface of the distal phalanx. It is usually caused by penetrating trauma, an abrasion, spread from adjacent tissues (e.g., eponychium, osteomyelitis, or paronychia), or a minor cut with invasion of bacteria. A felon can also develop in the presence of a foreign body, such as a wood splinter or a thorn.1 It can be iatrogenic from multiple fingersticks for glucose determination.2 The offending organism is usually Staphylococcus aureus. Mixed infections and gram-negative infections may occur in the immunocompromised patient. A felon can less commonly occur on the toes. The information in this chapter can be applied to a felon of the finger or the toe.
Felons initially present with a gradual onset of pain and erythema of the distal volar finger. Intense throbbing pain, warmth, and swelling develop with the formation of an abscess as the infection progresses. The proper treatment for a felon is incision and drainage. There are multiple techniques to incise and drain a felon. The patient requires digital elevation, immobilization, oral antistaphylococcal antibiotics, oral analgesics, and close follow-up to prevent complications following the incision and drainage.3–7
The distal finger consists of a closed compartment that is bound by the nail plate dorsally, by the skin ventrally and distally, and by the flexion crease proximally (Figure 108-1). This pulp region is divided by multiple (up to 15 or 20) vertical fibrous septa.8 These septa extend from the volar surface of the fat pad to the periosteum of the distal phalanx. They divide and compartmentalize the pulp area. When an abscess occurs, it is confined by the septa. They also limit the proximal spread of an infection. Unfortunately, they also inhibit the abscess from reaching the surface and inhibit drainage after the incision and drainage procedure. Blood is supplied by branches of the digital arteries that run parallel and lateral to the phalanx and terminate in the pulp region. The terminal branches of the digital nerves lie palmer and superficial to the arteries. The flexor digitorum profundus tendon inserts on the volar surface of the proximal distal phalanx.
Midsagittal section demonstrating the anatomy of the distal finger.
All felons that are fluctuant should be incised and drained. Volar digital pads that are tense, tender, painful, and suspected of containing a felon should be incised and drained regardless if fluctuance is palpated or not.
Felons that are not yet fluctuant, as in an early infection, may be treated with warm soaks, elevation, oral antibiotics, and follow-up in 24 hours.6,7 A herpetic whitlow can sometimes be confused with a felon.5,9 A herpetic whitlow can be clinically distinguished by the presence of multiple vesicles and a history of recurrence ...