SplintER Series: Case of the Swollen Finger

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]).

What is your diagnosis?

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.

How does this condition develop?

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].

What do you need to rule out? What are other diagnoses that should be considered in the Emergency Department?

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].

What is your management?

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.

References:

Rosh, Adam. Rosh Review website. Accessed April 22, 2021. https://www.roshreview.com/.
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.
Nardi NM, McDonald EJ, Schaefer TJ. Felon. In: StatPearls. Treasure Island (FL): StatPearls Publishing; July 20, 2020. PMID: 28613683.
Koshy JC, Bell B. Hand Infections. J Hand Surg Am. 2019;44(1):46-54. PMID: 30017648.
Rerucha CM, Ewing JT, Oppenlander KE, Cowan WC. Acute Hand Infections. Am Fam Physician. 2019;99(4):228-236. PMID: 30763047.

Author information

Kayla Prokopakis, DO

Resident
Emergency Medicine
St. Elizabeth Boardman Hospital

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