A felon is a subcutaneous infection or abscess in the pulp space on the palmar aspect of the fingertip (Figure 133-1). It is usually caused by penetrating trauma, an abrasion, spread from adjacent tissues (e.g., eponychium, osteomyelitis, or paronychia), or a minor cut that leads to the invasion of bacteria.1 A felon can develop in the presence of a foreign body (e.g., wood splinter or thorn).2 It can be iatrogenic from multiple fingersticks for blood glucose measurement.3,4 The offending organism is usually Staphylococcus aureus.5 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.
An example of a felon. (Used with permission from Knoop KJ, et al: The Atlas of Emergency Medicine, 4th ed. New York: McGraw-Hill; 2016. Photo contributor: Daniel L. Savitt, MD.)
Felons initially present with a gradual onset of pain and erythema of the distal volar finger consistent with symptoms of cellulitis.1 Intense throbbing pain, warmth, and swelling develop with the formation of an abscess as the infection progresses. The definitive management 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.6-10
ANATOMY AND PATHOPHYSIOLOGY
The distal finger consists of a closed compartment that is bound by the nail plate dorsally, the skin ventrally and distally, and the flexion crease proximally (Figure 133-2). The fingertip pulp region is divided by 15 to 20 vertical fibrous septa.11 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. An abscess in this enclosed space is confined by the septa which limits the proximal spread of an infection.12 The septa 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 ...