Felon

Presented by Yoon Cohen, D.O. & David Elpern, M.D.

Abstract: A 60-year-old woman with a 2-week history of skin infection on the tip of the 3rd finger

History: a 60-year-old woman presents with a 2-week history of skin infection on the tip of the left 3rd finger. She is diabetic and does a daily glucose check by finger prick. About 2 weeks ago, she has noticed a mild swelling where she had a finger prick, and treated herself at home with Epsom salt soak and cleaning with hydrogen peroxide solution. The lesion has been intensely tender to touch. She notes that had mild fever and chills 2 days prior to the visit.

The patient was hospitalized due to heart failure, and had a pacemaker and defibrillaor implanted 2 months prior. She handles horses and dogs at home, and she usually does not wear protective wears such as gloves.

O/E: A skin exam shows a well-appearing woman with a pink to erythematous markedly edematous abscess with yellowish drainage through a small punctum on the tip of the left 3rd finger. 

Clinical Photos:

At the initial visit

5 days after

Felon (Illustration by Renee L. Cannon)

Diagnostic Studies:

• Wound culture: Staphylococcus Aureus 3+; Serratia Liquefaciens 2+ (Gram negative rod)
• Radiograph: There is soft tissue swelling with likely ulcer formation involving the distal volar tip of the third phalanx. There is associated bony erosion involving the third distal phalanx worrisome for associated acute osteomyelitis

Diagnosis: Felon

Treatment: The patient was initially started on Keflex 500 mg four times daily with warm compress twice daily. Then we switched to Ciprofloxacin 250 mg twice daily after the wound culture report. We also lanced the lesion with a #11 blade to relieve pressure and drain. We are planning to refer the patient to an infectious disease specialist for a proper treatment of the underlying infection. 

Discussion: 

A felon is an abscess of the distal pulp or phalanx pad of the fingertip. The pulp of the fingertip is divided into small compartments by 15 to 20 fibrous septa that run from the periosteum to the skin. Abscess formation in these relatively noncompliant compartments causes significant pain, and the resultant swelling can lead to tissue necrosis. Because the septa attach to the periosteum of the distal phalanx, spread of infection to the underlying bone can result in osteomyelitis.

A felon usually is caused by inoculation of bacteria into the fingertip through a penetrating trauma. The most commonly affected digits are the thumb and index finger. Common predisposing causes include splinter, bits of glass, abrasions, and minor puncture wounds. A felon also may arise when an untreated paronychia spreads into the pad of the fingertip. Felons have been reported following multiple finger-stick blood tests.

Patients present with rapid onset of severe, throbbing pain, with associated redness and swelling of the fingertip. The pain caused by a felon is usually more intense than that caused by paronychia. The swelling will not extend proximal to the distal interphalangeal joint. Occasionally, the high pressure in the fingertip pad will cause a felon to spontaneously drain, resulting in a visible sinus.

If diagnosed in the early stages of cellulitis, a felon may be amenable to treatment with elevation, oral antibiotics, and warm water or saline soaks. Bone and soft tissue radiographs should be obtained to evaluate for osteomyelitis or a foreign body. Tetanus prophylaxis should be administered when necessary.

If fluctuance is present, incision and drainage are appropriate. Wound culture should be obtained to guide the optimal coverage of the underlying organisms. 

References:
1. Dwayne C, et al. Naval Hospital Jacksonville, Florida. Common Acute Hand Infections. Am Fam Physician. 2003. 1;68 (11):2167-76