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 the index finger [2-5]. 

• Pearl: The most common organism leading to a felon is staph aureus [2,5]

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 an 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 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 antibiotic and emergent ortho consult is necessary. 

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