A felon is a closed-space infection of the distal pulp (volar fat pad) of the fingertip, characterized by a tense, painful, swollen fingertip. The unique anatomy of the fingertip — with vertical fibrous septa connecting the periosteum to the skin — creates multiple closed compartments that trap infection and can lead to digital compartment syndrome, ischemic necrosis, and osteomyelitis if not promptly drained. [1-3]
1. History
- Mechanism of inoculation: Splinter, thorn, needle stick, nail biting, hangnail manipulation, minor laceration, or foreign body
- Timing: Onset typically 2–5 days after inoculation; progressive worsening of pain and swelling
- Pain characterization: Constant, throbbing pain in the fingertip pad; worsens with dependent positioning; often severe enough to disrupt sleep
- Which digit: Thumb and index finger most commonly affected
- Occupational/hobby exposures: Manual labor, gardening, fish/meat handling, IV drug use
- Prior episodes: Recurrent felons suggest retained foreign body or inadequate prior drainage
- Immunocompromising conditions: Diabetes, HIV, chemotherapy, chronic steroid use [3-4]
2. Alarm Features
- Fever, rigors, or lymphangitis → concern for systemic spread or deeper infection [5-6]
- Pain with passive extension of the finger or fusiform ("sausage") swelling → suspect pyogenic flexor tenosynovitis (Kanavel signs) [7]
- Erythema/swelling extending proximal to the DIP joint → concern for spread to flexor tendon sheath, deep space, or bone [1][6]
- Crepitus or skin necrosis → necrotizing soft tissue infection [8]
- Failure to improve after I&D → consider osteomyelitis, retained foreign body, or herpetic whitlow misdiagnosed as felon [2-3]
3. Medications
- Empiric oral antibiotics (adjunct to I&D or for early/mild felons):
- TMP-SMX DS (1 DS tab BID) or clindamycin (300–450 mg TID) — provides MRSA coverage [9-10]
- Amoxicillin-clavulanate if bite-related etiology [11]
- Duration: 7–10 days [2][12]
- MRSA coverage is recommended empirically given that MRSA accounts for ~50% of hand infection cultures in urban settings [9][13]
- IV antibiotics (vancomycin, ampicillin-sulbactam) if systemic signs, immunocompromised, or concern for deep space extension [12][14]
- Contraindicated: Do NOT incise a herpetic whitlow — this can cause secondary bacterial superinfection and viral dissemination [2][4]
- Tetanus prophylaxis should be updated if indicated [2]
4. Diet
- No specific dietary triggers or recommendations
- Diabetes management: Optimize glycemic control, as diabetes is a strong predictor of polymicrobial infection and poor wound healing [13]
5. Review of Systems
- Constitutional: Fever, chills, malaise (suggests systemic infection)
- MSK: Pain with finger movement, stiffness, reduced grip strength
- Skin: Lymphangitic streaking, proximal erythema, draining sinus
- Vascular: Assess for signs of digital ischemia (pallor, delayed cap refill) — compartment pressure from pus can compromise digital arteries [1]
6. Collateral History and Family History
- Occupational history: Manual laborers, healthcare workers (needle sticks), fishermen, butchers
- Social history: IV drug use is a strong predictor of polymicrobial and more aggressive infections [13]
- Immunosuppression: Medications, HIV status, organ transplant
- Family history is generally not contributory
7. Risk Factors
- Penetrating trauma to the fingertip (most common cause) [2][4]
- Nail biting / hangnail manipulation [3]
- Diabetes mellitus [13]
- IV drug use [13]
- Immunosuppression (HIV, chemotherapy, chronic steroids) [3]
- Splinters, thorns, foreign bodies [2]
- Extension from untreated paronychia [1]
8. Differential Diagnosis
- Herpetic whitlow — Grouped vesicles on an erythematous base; often less tense than a felon; may have prodromal tingling; do NOT incise [2][4]
- Paronychia — Infection of the nail fold rather than the pulp; fluctuance is periungual, not volar [1]
- Pyogenic flexor tenosynovitis — Kanavel signs (fusiform swelling, flexed posture, pain with passive extension, tenderness along tendon sheath); a surgical emergency [7]
- Distal phalanx osteomyelitis — Complication of untreated felon; suspect if refractory to I&D [15]
- Inclusion (epidermoid) cyst — Non-tender, slow-growing; may become inflamed and mimic felon [3]
- Gout/pseudogout — Rare in the DIP; crystal arthropathy can mimic infection
- Foreign body granuloma — History of penetrating injury with persistent swelling [3]
- Mucous cyst — Dorsal DIP, associated with osteoarthritis; not volar
9. Past Medical History
- Diabetes — Higher risk of polymicrobial infection, poor healing, and need for operative intervention [13]
- Peripheral vascular disease — Impaired healing
- Prior hand infections or surgeries — Altered anatomy, scar tissue
- Immunosuppressive medications — Biologics, steroids, chemotherapy
- Recurrent MRSA infections — Consider decolonization
10. Physical Exam
- Inspection: Tense, erythematous, swollen distal fingertip pulp; may have a visible pointing abscess
- Palpation: Exquisitely tender, fluctuant volar pad; loss of normal skin wrinkles over the pulp
- Assess for Kanavel signs (to rule out flexor tenosynovitis): [7]
- Fusiform (sausage-shaped) swelling of the entire finger
- Flexed posture at rest
- Pain with passive extension
- Tenderness along the flexor tendon sheath
- Lymph nodes: Check epitrochlear and axillary nodes
- Lymphangitic streaking: Red streaks tracking proximally
- Neurovascular exam: Capillary refill, two-point discrimination (baseline before any procedure)
- Vital signs: Fever and tachycardia suggest systemic involvement [12]
11. Lab Studies
- Routine labs are generally unnecessary for uncomplicated felons
- Wound culture (Gram stain and culture of purulent material at time of I&D) — recommended to guide antibiotic therapy, especially given high MRSA prevalence [12-13]
- CBC, CRP, ESR — if concern for systemic infection, osteomyelitis, or deep space infection [8]
- Blood cultures — if febrile, immunocompromised, or signs of sepsis
- Blood glucose / HbA1c — if diabetes suspected or known [13]
12. Imaging
- X-ray of the affected digit (AP and lateral):
- First-line — rule out foreign body, osteomyelitis (periosteal reaction, cortical erosion), and fracture [15-16]
- Should be obtained before I&D in most cases
- Ultrasound: Can confirm fluid collection and guide drainage; useful when clinical exam is equivocal [16]
- MRI: Gold standard for osteomyelitis or deep space infection if suspected; not routinely needed [15]
- CT: May be useful in complex cases to delineate deep space involvement [16]
- Imaging is unnecessary for a straightforward, clinically obvious felon without concern for complications
13. Special Tests
- Point-of-care ultrasound (POCUS): Helpful to confirm abscess vs. cellulitis and identify foreign bodies
- Two-point discrimination: Baseline before digital block; important for medicolegal documentation
- Allen test: If concern for vascular compromise
- Tzanck smear or HSV PCR: If herpetic whitlow is suspected (grouped vesicles, clear fluid, recurrent episodes) [4]
14. ECG
- Not routinely indicated
- Obtain if the patient is septic or requires procedural sedation
15. Assessment
A felon is a closed-space abscess of the fingertip pulp. The vertical fibrous septa create compartments that trap infection, leading to increased pressure, ischemia, and potential necrosis of the fat pad, skin, or distal phalanx. [1-2] Staphylococcus aureus (including MRSA) is the most common causative organism, accounting for >75% of cases; Streptococcus species and gram-negatives are less common. [11][13-14]
Severity stratification:
- Early/mild: Erythema, mild swelling, tenderness without fluctuance → may trial antibiotics + warm soaks
- Moderate: Tense, fluctuant pulp with significant pain → requires I&D
- Severe/complicated: Systemic signs, extension beyond the pulp, osteomyelitis → IV antibiotics + surgical consultation [1-2][6]
16. Treatment Plan
Early felon (no fluctuance)
- Warm soaks (20 min, 3–4× daily), elevation, splinting in position of function
- Empiric oral antibiotics with MRSA coverage (TMP-SMX DS or clindamycin) for 7–10 days [1-2]
- Close follow-up in 24–48 hours
Established felon (fluctuant abscess) — Incision and Drainage:
- Digital block (digital nerve block preferred; avoid epinephrine in compromised digits)
- Incision approach: [1][17]
- Superficial abscess: Longitudinal volar incision directly over the point of maximal fluctuance
- Deep abscess: Unilateral mid-lateral incision on the non-contact (ulnar) side of the digit (radial side for the thumb/small finger)
- Do NOT extend the incision proximal to the DIP flexion crease (risk of flexor tendon sheath violation) [1]
- Hockey stick or fish mouth incisions are generally avoided due to risk of unstable/painful scar and vascular compromise; reserved for very large collections [1]
- Break up septae with a blunt hemostat to ensure complete drainage
- Irrigate the cavity
- Loosely pack with iodoform gauze wick (remove in 48 hours)
- Splint in position of function
- Empiric oral antibiotics with MRSA coverage × 7–10 days [10][12]
- Tetanus prophylaxis if indicated [2]
Severe/complicated
- IV antibiotics (vancomycin ± piperacillin-tazobactam if polymicrobial concern)
- Hand surgery consultation for operative drainage, especially if concern for osteomyelitis or deep space extension [6][18]
17. Disposition
- Discharge: Uncomplicated felon after successful I&D, reliable patient, no systemic signs
- Observation/admission criteria:
- Systemic signs of infection (fever, tachycardia, leukocytosis)
- Immunocompromised host
- Concern for deep space infection, flexor tenosynovitis, or osteomyelitis
- Failed outpatient management
- Need for IV antibiotics [4][6]
- Surgical consultation triggers:
- Kanavel signs (flexor tenosynovitis) — emergent [7]
- Suspected osteomyelitis
- Extensive tissue necrosis
- Recurrent or refractory felon
18. Follow Up / Return Precautions
- Follow-up in 24–48 hours for wound check and packing removal
- Return precautions — instruct patient to return immediately for:
- Worsening pain, swelling, or redness
- Fever or chills
- Red streaking up the arm
- Numbness or color change of the fingertip
- Purulent drainage not improving after 48 hours
- Expected course: Significant improvement within 48–72 hours after adequate drainage; full healing in 2–3 weeks
- Wound care: Warm soaks after packing removal, keep clean and dry, elevation
- Culture follow-up: Adjust antibiotics based on culture and sensitivity results
- Hand therapy referral if stiffness develops [19]
References
1. Management of Finger Felons and Paronychia: A Narrative Review. — Gottlieb M, Long B. The Journal of Emergency Medicine. 2025.
2. Common Acute Hand Infections. — Clark DC. American Family Physician. 2003.
3. Fingertip Infections. — Barger J, Hoyer RW. The Orthopedic Clinics of North America. 2024.
4. Acute Hand Infections. — Rerucha CM, Ewing JT, Oppenlander KE, Cowan WC. American Family Physician. 2019.
5. Hand Infections. — Brown H. American Family Physician. 1978.
6. Infections of Deep Hand and Wrist Compartments. — Malizos KN, Papadopoulou ZK, Ziogkou AN, et al. Microorganisms. 2020.
7. High Risk and Low Prevalence Diseases: Flexor Tenosynovitis. — Mehta P, Thoppil J, Koyfman A, Long B. The American Journal of Emergency Medicine. 2024.
8. Diagnosis and Management of Upper Limb Soft Tissue Infections. — Auquit-Auckbur I, Beccari R, Coquerel-Beghin D, Garcia-Doldan CM. Orthopaedics & Traumatology, Surgery & Research : OTSR. 2025.
9. A 39-Year-Old Man With a Skin Infection. — Moellering RC. The Journal of the American Medical Association. 2008.
10. A Placebo-Controlled Trial of Antibiotics for Smaller Skin Abscesses. — Daum RS, Miller LG, Immergluck L, et al. The New England Journal of Medicine. 2017.
11. Susceptibility of Microorganisms Causing Acute Hand Infections. — Fuchsjäger N, Winterleitner H, Krause R, Feierl G, Koch H. PloS One. 2019.
12. Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of America. — Stevens DL, Bisno AL, Chambers HF, et al. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2014.
13. Epidemiology of Adult Acute Hand Infections at an Urban Medical Center. — Fowler JR, Ilyas AM. The Journal of Hand Surgery. 2013.
14. Hand Infections. — McDonald LS, Bavaro MF, Hofmeister EP, Kroonen LT. The Journal of Hand Surgery. 2011.
15. Hand Infections: Anatomy, Types and Spread of Infection, Imaging Findings, and Treatment Options. — Patel DB, Emmanuel NB, Stevanovic MV, et al. Radiographics : A Review Publication of the Radiological Society of North America, Inc. 2014.
16. MDCT of Hand and Wrist Infections: Emphasis on Compartmental Anatomy. — Ahlawat S, Corl FM, LaPorte DM, Fishman EK, Fayad LM. Clinical Radiology. 2017.
17. Treatment of Felons. — Kilgore ES, Brown LG, Newmeyer WL, Graham WP, Davis TS. American Journal of Surgery. 1975.
18. Hand Infections. — Franko OI, Abrams RA. The Orthopedic Clinics of North America. 2013.
19. Management of Pyogenic Flexor Tenosynovitis. — Anderson GM, Proal JD, Crowe CS, Kennedy SA. JBJS Reviews. 2026.