Differential diagnosis for a felon includes herpetic whitlow.
Fingertip pulp is divided into numerous small compartments by vertical septa that stabilize the pad. Infection occurring within these compartments can lead to abscess formation, edema, and rapid development of increased pressure in a closed space. This increased pressure may compromise blood flow and lead to necrosis of the skin and pulp.
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Felons and paronychias account for approximately one third of all hand infections. Thumb and index finger are the most commonly affected digits.
With skin necrosis, spontaneous decompression may occur. When skin does not yield, osteomyelitis, tenosynovitis, and septic arthritis may result.
Wooden splinters, thorns, or minor cuts are common predisposing causes, yet no history of injury exists in over one half of patients. Infection also may spread from a paronychia.
The infection often begins as cellulitis, which is initially confined by the tough fibrous septa that course throughout the pad. At this stage, patients may report pain, redness, and swelling. Mild infections may resolve with antibiotics.
If resolution does not occur, abscess formation is accompanied by progression of swelling and intense throbbing pain.
A felon is characterized by a fingertip pad that is erythematous, tensely swollen, and very tender to palpation. There may be an associated puncture wound or paronychia.
If the infection has spread to the flexor tendon sheath, the entire finger may be erythematous, swollen, and held semi-flexed.
Staphylococcus aureus is the most common cause of felon and is often methicillin-resistant (MRSA).[3, 4, 5]
Gram-negative organisms have been reported in immunosuppressed patients. Lancet-induced trauma from fingertip blood glucose measurements have been implicated as an etiology.
Eikenella corrodens has been reported in persons with diabetes who bite their fingernails.[3, 6, 7]
Radiographs should be obtained if there is a history of penetration with a radiopaque foreign body.
Felons that are untreated, incorrectly treated, or have a prolonged course may lead to osteomyelitis. Radiographic evaluation should be performed in severe cases and in immunocompromised patients.
Adequate early treatment of a felon can prevent abscess formation and other serious complications.
Administer antibiotics with activity against methicillin-resistant Staphylococcus.
Decompression is essential to preserve blood flow, whether or not a frank abscess has formed.
A digital block provides adequate local anesthesia.
Incisions near the midline of the pad are least likely to injure nerves or blood vessels.
Make a short skin incision with a number 11 blade over the area of maximum swelling and tenderness. Incise only the skin.
Evacuate pus using a blunt instrument in order to decrease the chance of severing the nerve or entering the tendon sheath. Do not divide vertical fascial strands (septa). For further information, see Hand, Paronychia Drainage.
Culture any drainage.
Pack gauze loosely into the wound to prevent skin closure. Apply a loose dressing, splint the finger, and elevate the hand above the heart.
Update tetanus immunization.
High lateral incisions, palmar longitudinal incisions, palmar transverse incisions, and hockey stick and fishmouth incisions have been recommended in the past. Some of these incisions offer no benefit but increase the potential for serious injury.
The felon should be incised in the area of maximum swelling and tenderness. The incision should not cross the distal interphalangeal (DIP) joint to prevent formation of a flexion contracture at the DIP flexion crease. Probing is not carried out proximally to avoid extension of infection into the flexor tendon sheath.
A longitudinal incision in the midline is effective without serious iatrogenic complications that are observed with other traditionally recommended incisions.
Lateral or transverse incisions frequently cause ischemia and anesthesia by injuring one or both neurovascular bundles.
Fish-mouth incision can lead to an unstable painful fingertip.
An orthopedist or hand surgeon should be consulted for more complex cases, especially when there is concern for osteomyelitis or flexor tenosynovitis.
Because of the potential for complications, prompt follow-up should be arranged in all cases. Surgical consultation should be obtained if there is no improvement within 12-24 hours of conventional therapy.
If treated early, drainage, elevation, and oral antibiotics may be adequate. Appropriate follow-up should always be arranged. Severe infections and complicated cases may require hospitalization for intravenous antibiotics and surgical drainage.
The most common organism involved is S aureus, accounting for around 80% of cases. Empiric coverage for MRSA is recommended. Gram stain, if available, should be used to guide therapy.
Provide tetanus prophylaxis if appropriate.
If drainage and antibiotic therapy yield no improvement within 12-24 hours, consultation with a surgeon is recommended.
Potential complications of felon include fingertip necrosis, osteomyelitis, and/or flexor tenosynovitis.
The goals of pharmacotherapy are to treat infections and prevent further complications.
Clinical Context: Bactericidal antibiotic that inhibits cell wall synthesis; DOC to treat infections caused by penicillinase-producing staphylococci. May be used to initiate therapy when staphylococcal infection is suspected.
Clinical Context: Another alternative antibiotic. First-generation cephalosporin that inhibits bacterial replication by inhibiting bacterial cell wall synthesis. Bactericidal and effective against rapidly growing organisms forming cell walls.
Clinical Context: Inhibits bacterial growth by inhibiting synthesis of dihydrofolic acid.
Clinical Context: Semisynthetic antibiotic produced by 7(S)-chloro-substitution of 7(R)-hydroxyl group of parent compound lincomycin. Inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. Widely distributes in the body without penetration of CNS. Protein bound and excreted by the liver and kidneys.
Clinical Context: Amoxicillin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins. Addition of clavulanate inhibits beta-lactamase producing bacteria.
Good alternative antibiotic for patients allergic or intolerant to the macrolide class. Usually is well tolerated and provides good coverage to most infectious agents. Not effective against Mycoplasma and Legionella species. The half-life of oral dosage form is 1-1.3 h. Has good tissue penetration but does not enter cerebrospinal fluid.
For children >3 months, base dosing protocol on amoxicillin content. Due to different amoxicillin/clavulanic acid ratios in 250-mg tab (250/125) vs 250 mg chewable-tab (250/62.5), do not use 250-mg tab until child weighs >40 kg.
Clinical Context: Indicated for severe infections.
Treats infections caused by penicillinase-producing staphylococci. Used to initiate therapy in any patients with possible penicillin G-resistant staphylococcal infection. Do not use for treatment of penicillin G-susceptible staphylococcal organisms.
Use parenteral therapy initially in severe infections. Severe infections may require very high doses.
Change to oral therapy as condition improves.
Because of occasional occurrence of thrombophlebitis associated with the parenteral route, particularly in elderly patients, administer parenterally only for a short term (24-48 h) and change to oral route if clinically possible.
Clinical Context: Broad-spectrum, synthetically derived bacteriostatic antibiotic in the tetracycline class. Almost completely absorbed, concentrates in bile, and is excreted in urine and feces as a biologically active metabolite in high concentrations.
Inhibits protein synthesis and, thus, bacterial growth by binding to 30S and possibly 50S ribosomal subunits of susceptible bacteria. May block dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest.
Provides good coverage against Spirochetes, many gram-negative organisms, anaerobic organisms, atypical bacteria, and many gram-positive organisms.
Empirical coverage for S aureus and streptococcal organisms should be provided. While a first-generation cephalosporin or antistaphylococcal penicillin has traditionally been recommended, the rapid emergence of community-acquired methicillin-resistant S aureus (CA-MRSA) requires treatment with drugs more likely to be effective against this agent. Trimethoprim/sulfamethoxazole or clindamycin should be added for this coverage. Coverage for E corrodens may be indicated for immunosuppressed patients and bite wounds. Tailor antibiotics to cultures and sensitivities. Continue antibiotics for 7-10 days.
Splint and elevate finger.
Provide follow-up care within 2 days.
Remove packing in 2 days.
Osteomyelitis involving the diaphysis of distal phalanx is a common complication.
The most serious complication of felon is acute tenosynovitis, which may result from contiguous spread of infection. This can be iatrogenic from inadvertent nicking of the flexor tendon sheath during drainage.
Other complications include skin necrosis, deformity of the fingertip, septic arthritis, and instability of the finger pad.
Differential diagnosis for a felon includes herpetic whitlow.
A paronychia can progress to a felon if left untreated.
Drainage of pus from under perionychium in a paronychia.
