Felon


Article Author:
Naomi Nardi


Article Editor:
Timothy Schaefer


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Chaddie Doerr


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Tehmina Warsi


Updated:
12/19/2018 7:33:38 AM

Introduction

A felon is an infection that occurs within the closed-space compartments of the fingertip pulp.  The swelling leads to intense throbbing pain. The surrounding tissues are at risk for ischemia if the blood flow is compromised by compression from edema and pus formation. Treatment involves incision and drainage of the infected pulp space and oral antibiotics. If left untreated the underlying bone, joint, or tendons may become infected.[1][2]

Etiology

Any injury to the fingertip may predispose to a felon including minor cuts, foreign body penetrations, splinters, and paronychias. Staphylococcus aureus is the most common bacteria associated with felons.  Gram-negative organisms can be found in immuno-suppressed individuals.[3][4]

Epidemiology

Felons, along with paronychias, account for almost one-third of hand infections. Felons most commonly occur in the first and second digits of the hand. They are most commonly caused by penetrating trauma. However, anything that introduces bacteria into the digital pulp can lead to felon formation.  Splinters, puncture wounds, bits of glass, abrasions, or bites can all be inciting factors. Paronychias are another common cause.[5][6]

Pathophysiology

A felon is an infection that occurs within the closed-space compartments of the fingertip pulp. The infection may initially start as cellulitis which can progress to abscess formation if not treated early. The compartments of the fingertip are divided by vertical fascial strands known as ‘septae’ which run from the periosteum of the distal phalanx to the skin. These fibrous septae provide structural support to the pulp and form small compartments. Blood flow may be compromised when edema and infection form in these non-compliant compartments which in turn can lead to skin and pulp necrosis. The swelling in these small compartments causes the severe pain associated with felons. Septae may also impede complete drainage after and an incision and drainage procedure if they are not properly separated. If not properly treated, felons can progress to osteomyelitis, tenosynovitis, and septic arthritis.

History and Physical

The patient may recall trauma to the finger, but often no inciting source is identified.  The patient may describe that they first noticed erythema of the finger tip, which later became edematous and painful. The pain may be mild at first but rapidly progress to severe and throbbing.

The presenting symptoms include tissue tension, throbbing pain, edema, and erythema of the fingertip pulp at the distal phalanx. Typically, the edema will not extend proximally to the distal phalanx due to the compartments defined by the septae. The pain is often severe and worse in the dependent position. Spontaneous drainage may occur due to the pressure in the fingertip which may result in temporary relief. However, if not properly incised and drained, the abscess will reform.

Evaluation

The diagnosis can often be made based on clinical exam. The distal phalanx may be erythematous and edematous with tense tissues and fluctuance.  The fingertip may be extremely tender to the touch. It is important to note any bony abnormalities and assess for signs of ischemia. Imaging should be performed if there is a history of a foreign body penetration. Imaging can also identify fractures, osteomyelitis, and gas formation in the tissues which may lead to an alternative diagnosis.  A gram stain and culture of any discharge or drainage should be obtained to help guide antibiotic therapy.

Treatment / Management

If abscess formation has not yet occurred and the felon is in the cellulitis stage, it can be treated with anti-staphylococcal and anti-streptococcal antibiotics. Warm water or saline soaks, and elevation of the fingertip will also aid in recovery. If abscess formation has occurred, or if tension or fluctuance are present, incision and drainage must be performed to drain infected material and maintain venous blood flow to the finger. Due to the fibrous septae forming multiple compartments, it may be difficult to fully drain a felon and debridement in an operating room may be necessary.[7][8][9]

A digital block should be performed prior to incision and drainage. Bupivacaine has the advantage of a longer lasting anesthetic effect than lidocaine. A finger tourniquet can be used to decrease bleeding and aid in visualization of structures.  The area of maximal swelling and tenderness should be located for optimal drainage. For deep felons, a single lateral incision should be made. The incision should be made at least 0.5 cm distal to the DIP in order to avoid injury to the flexor tendon sheath, digital neurovascular structures, nail matrix and to avoid contracture. The incision should extend parallel to the nail plate.  It is important to maintain a distance of 0.5 cm from the nail plate to avoid injury. The incision should be made on the nonoppositional side of the appropriate digit.  The incision should be made on the ulnar aspect of digits 2, 3, or 4 and on the radial aspect of digits 1 and 5. The depth of the incision should be to the dermis. The incision should be extended to the end of the nail. For complete drainage, it is often necessary to use blunt dissection to separate the finger septae with a small blunt hemostat. If there is necrotic tissue present, it should be excised, and the abscess should then be decompressed and irrigated.  The wound should be packed, and the finger should be splinted.

A volar longitudinal incision can be used for superficial felons. The same precautions as stated above should be followed.  It is not recommended to use the “fish-mouth” incision, the “hockey stick” or the transverse palmar incision, as these incisions have been associated with complications such as neurovascular damage and painful scarring.

Packing should be removed in 48 to 72 hours, and the finger should be re-examined by a physician. If there is an improvement and the wound appears to be healing, the packing should be removed, and the wound can be allowed to close by secondary intention.  If there is no improvement within 12-24 hours, or if the felon is extensive or recurrent, a surgical consult may be needed.

The patient should receive a tetanus shot if not up to date.  A first-generation cephalosporin or anti-staphylococcal penicillin to cover S aureus and streptococcal organisms should be prescribed for 7-10 days. Doxycycline, trimethoprim/sulfamethoxazole, or clindamycin can be added if there is suspicion for MRSA. If the felon was a result of a bite wound, or if the patient is immunosuppressed, coverage for E corrodens may be indicated.  Gram stain should be used to guide therapy when available.

Enhancing Healthcare Team Outcomes

A felon is a very common presentation and healthcare workers including nurse practitioners should be familiar with its management. Mild cases can be treated with warm soaks and an antibiotic but if fluctuance is present, then drainage is required. Before one starts to make an incision, it is important to know the anatomy of the fingertip to avoid causing any iatrogenic injury. The outcomes for most patients are excellen.


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Felon - Questions

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A patient presents with finger pain and swelling. She cannot remember a specific injury to the finger. She states that she noticed her left index finger was red a few days ago. This morning she woke up, and her finger was swollen and very red. She complains of a throbbing pain and feels as though she can’t bend her finger because of the swelling. On exam, the patient’s left index finger is erythematous and edematous on the palmar aspect of the left index finger from the DIP to the finger tip. The tissue is tense and tender to the touch. Vitals are within normal limits. What is the next appropriate step?



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After incising and draining a felon on a patient's finger, the patient needs an antibiotic. What is the most common bacteria associated with a felon?



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Felon - References

References

Koshy JC,Bell B, Hand Infections. The Journal of hand surgery. 2018 Jul 13;     [PubMed]
Blumberg G,Long B,Koyfman A, Clinical Mimics: An Emergency Medicine-Focused Review of Cellulitis Mimics. The Journal of emergency medicine. 2017 Oct;     [PubMed]
Rabarin F,Jeudy J,Cesari B,Petit A,Bigorre N,Saint-Cast Y,Fouque PA,Raimbeau G, Acute finger-tip infection: Management and treatment. A 103-case series. Orthopaedics     [PubMed]
Pierrart J,Delgrande D,Mamane W,Tordjman D,Masmejean EH, Acute felon and paronychia: Antibiotics not necessary after surgical treatment. Prospective study of 46 patients. Hand surgery     [PubMed]
Imahara SD,Friedrich JB, Community-acquired methicillin-resistant Staphylococcus aureus in surgically treated hand infections. The Journal of hand surgery. 2010 Jan;     [PubMed]
Tannan SC,Deal DN, Diagnosis and management of the acute felon: evidence-based review. The Journal of hand surgery. 2012 Dec;     [PubMed]
Patel DB,Emmanuel NB,Stevanovic MV,Matcuk GR Jr,Gottsegen CJ,Forrester DM,White EA, Hand infections: anatomy, types and spread of infection, imaging findings, and treatment options. Radiographics : a review publication of the Radiological Society of North America, Inc. 2014 Nov-Dec;     [PubMed]
Hijjawi JB,Dennison DG, Acute felon as a complication of systemic paclitaxel therapy: case report and review of the literature. Hand (New York, N.Y.). 2007 Sep;     [PubMed]
Shmerling RH, Finger pain. Primary care. 1988 Dec;     [PubMed]

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