An 18-year-old male presents with a painful and swollen left thumb. He removed a splinter from his finger a few days ago however, 2 days after removal, he began to experience edema and pain that has progressively gotten worse. An image of his finger is shown above (Image 1. Picture courtesy of Rosh Review [1]).


The patient has a felon. A felon is a subcutaneous abscess in the finger pulp. The most common location for a felon is the thumb or index finger [2-5].

  • Pearl: The most common organism leading to a felon is Staph aureus.
The mechanism for the development of a felon can occur secondary to penetration from a foreign body, minor trauma from biting the fingernail, local spread from a paronychia, or idiopathic. There are microcompartments in the finger and when infection arises, the swelling can be severe enough to cause compartment syndrome [2-5].

  • Pearl: A felon differs from a paronychia as a felon is in the pulp and usually presents on the pad of the finger while a paronychia is in the epidermis along the nail fold [2,5].
Flexor tenosynovitis! This is potentially a finger and/or hand-threatening infection. The location of swelling can differentiate between flexor tenosynovitis and a felon. The swelling in a felon does not extend proximal past the distal interphalangeal joint [4,5]. If it does, there is concern that the infection has spread into the flexor sheath and IV antibiotics and emergent ortho consultation are necessary.

  • Pearl: TO identity flexor tenosynovitis utilize the Kanavel signs [4,5].
The management of a felon is similar to that of an abscess. Initial management can include warm compresses and supportive care. The definitive treatment is incision and drainage [2-5]. The use of antibiotics after drainage is controversial but if they are prescribed, should cover Staph aureus.

  • Pearl: The incision for the I&D should be made distal to the distal interphalangeal joint on the ulnar side for digits 2-4 and the radial side for the thumb and 5th digit [2]. A digital block should be considered from adequate analgesia during the procedure. See EM:RAP HD for a video review of the felon I&D procedure.



  1. Rosh, Adam. Rosh Review website. Accessed April 22, 2021. https://www.roshreview.com/
  2. Stapczynski, JS, Tintinalli, JE. Musculoskeletal Disorders: Felon. Tintinalli’s emergency medicine: A comprehensive study guide, 8th Edition. New York, NY: McGraw-Hill Education; 2016: 1924.
  3. Nardi NM, McDonald EJ, Schaefer TJ. Felon. In: StatPearls. Treasure Island (FL): StatPearls Publishing; July 20, 2020. PMID: 28613683.
  4. Koshy JC, Bell B. Hand Infections. J Hand Surg Am. 2019;44(1):46-54. PMID: 30017648.
  5. Rerucha CM, Ewing JT, Oppenlander KE, Cowan WC. Acute Hand Infections. Am Fam Physician. 2019;99(4):228-236. PMID: 30763047.
Kayla Prokopakis, DO

Kayla Prokopakis, DO

Emergency Medicine
St. Elizabeth Boardman Hospital
Kayla Prokopakis, DO

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Matthew Negaard, MD

Matthew Negaard, MD

Clinical Assistant Professor
Department of Emergency Medicine
University of Iowa Hospitals and Clinics

Primary Care Sports Medicine Physician
Methodist Sports Medicine (Indianapolis, Indiana)
Matthew Negaard, MD

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Alexander J. Tomesch, MD

Alexander J. Tomesch, MD

Primary Care Sports Medicine Fellow
Department of Orthopedic and Sports Medicine
University of Arizona - Tucson
Alexander J. Tomesch, MD

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