01Approach to the Critical Patient/attcp31

Immediate priorities

›Time-critical recognition

›Felon is a closed-space infection of the distal fingertip pulp

›Vertical fibrous septa create isolated compartments that trap infection

›Rising compartment pressure leads to digital ischemic necrosis if untreated

›Emergent consultation triggers

›Kanavel signs present — suspect pyogenic flexor tenosynovitis (surgical emergency)

›Crepitus or skin necrosis — suspect necrotizing soft tissue infection

›Signs of sepsis with digital infection source

Red flag recognition

›Conditions requiring immediate escalation

›Pyogenic flexor tenosynovitis

›Fusiform sausage-shaped swelling of entire finger

›Flexed posture at rest

›Pain with passive extension

›Tenderness along flexor tendon sheath

›Necrotizing soft tissue infection

›Skin necrosis or bullae

›Crepitus on palpation

›Disproportionate pain

›Septic presentation

›Fever, tachycardia, leukocytosis with hand infection

›Lymphangitic streaking proximal to DIP

Key decision branch

›Severity stratification

›Early/mild — erythema, tenderness without fluctuance

›Trial oral antibiotics and warm soaks

›Close follow-up in 24–48 hours

02History/hx34

Onset and mechanism

›Inoculation mechanism

›Splinter or thorn penetration

›Needle stick (healthcare workers, IV drug users)

›Nail biting or hangnail manipulation

›Minor laceration or abrasion to fingertip pad

›Foreign body retained in pulp space

Symptom characterization

›Pain features

›Constant throbbing pain in the fingertip pad

›Worsens with dependent positioning

›Severe enough to disrupt sleep

›Onset typically 2–5 days after inoculation

›Progressive worsening over days if untreated

Alarm symptoms

›Systemic spread indicators

›Fever or rigors — concern for systemic dissemination

›Red streaking tracking proximally — lymphangitis

›Pain with passive finger extension — flexor tenosynovitis

›Numbness or color change of fingertip — vascular compromise

Digit affected

›Anatomic predilection

›Thumb and index finger most commonly affected

›Dominant hand more often involved due to exposure risk

Exposures and occupational history

›High-risk occupational and behavioral exposures

›Manual labor and gardening

›Fish or meat handling

03Physical Exam/exam32

Vital signs

›Systemic assessment

›Fever and tachycardia — suggest systemic involvement

›Hypotension — septic shock from hand infection (rare but life-threatening)

Inspection of affected digit

›Gross morphology

›Tense, erythematous, swollen distal fingertip pulp

›Visible pointing abscess at site of maximal fluctuance

›Loss of normal skin wrinkles over the pulp

›Bullae or skin necrosis — necrotizing infection

Palpation

›Local findings

›Exquisitely tender volar pad on palpation

›Fluctuance of the fingertip pulp (confirms abscess)

›Warmth and induration of the distal phalanx

Kanavel signs assessment

›Four cardinal signs of flexor tenosynovitis (all must be sought)

›Fusiform sausage-shaped swelling of entire finger

›Flexed posture at rest

›Pain with passive extension of the finger

›Tenderness along the flexor tendon sheath from DIP to palm

Lymphatic and proximal spread

›Regional assessment

›Lymphangitic streaking proximal to the DIP joint

›Epitrochlear and axillary lymphadenopathy

›Erythema or swelling extending proximal to DIP — concern for deeper extension

Neurovascular exam

›Baseline neurovascular status

04Differential Diagnosis/ddx42

Fingertip infections

›Herpetic whitlow

›ICD-10: B00.89

›Grouped vesicles on erythematous base; prodromal tingling

›Do NOT incise — causes secondary bacterial superinfection and viral dissemination

›Tzanck smear or HSV PCR confirms diagnosis

›Paronychia

›ICD-10: L03.011–L03.019

›Infection of nail fold rather than volar pulp

›Periungual fluctuance without volar tense swelling

Deeper hand infections

›Pyogenic flexor tenosynovitis

›ICD-10: M65.141–M65.149

›Surgical emergency requiring emergent hand surgery consultation

›Kanavel signs distinguish from felon

›Infection tracks along flexor tendon sheath from DIP to palm

›Deep space infection

›ICD-10: L03.111–L03.119

›Thenar, hypothenar, mid-palmar space

›Swelling extends proximal to DIP flexion crease

Bone and joint

›Distal phalanx osteomyelitis

›ICD-10: M86.141–M86.149

›Complication of untreated felon

›Periosteal reaction or cortical erosion on plain radiograph

›MRI gold standard for diagnosis

›Septic arthritis of DIP joint

›ICD-10: M00.041–M00.049

05Laboratory Tests/lt26

Wound culture

›Gram stain and culture of purulent material

›Obtained at time of incision and drainage

›Essential given MRSA accounts for approximately 50% of hand infection cultures in urban settings

›Guides antibiotic de-escalation or escalation based on sensitivities

Inflammatory markers

›Markers for systemic or bone involvement

›Complete blood count — leukocytosis with left shift indicates systemic infection

›C-reactive protein — elevated in osteomyelitis and deep space infection

›Erythrocyte sedimentation rate — sensitive but non-specific for osteomyelitis

›All indicated when concern for systemic infection, osteomyelitis, or deep space extension

Blood cultures

›Indications for blood cultures

›Febrile patient with hand infection

›Immunocompromised host

›Signs of sepsis (tachycardia, hypotension, altered mental status)

Glucose and metabolic

›Glucose and HbA1c

›Obtain if diabetes suspected or known

›Hyperglycemia predicts polymicrobial infection and poor wound healing

›HbA1c guides glycemic optimization plan

Microbiology considerations

›Expected pathogens

›Staphylococcus aureus including MRSA — most common, accounts for greater than 75% of cases

›Streptococcus species — less common

›Gram-negative organisms — rare, consider in immunocompromised or IV drug users

›Polymicrobial — more common in diabetics and IV drug users

06Diagnostic Tests/dt52

Scoring Systems

›Severity stratification framework

›Early/mild felon

›Erythema and tenderness without fluctuance

›No systemic signs

›Management: oral antibiotics plus warm soaks plus close follow-up

›Moderate felon

›Tense fluctuant pulp

›Significant pain, no systemic signs

›Management: incision and drainage plus oral antibiotics

›Severe/complicated felon

›Systemic signs of infection (fever, leukocytosis)

›Extension beyond pulp or concern for osteomyelitis

›Management: IV antibiotics plus surgical consultation plus possible admission

MRI

›Indications for MRI

›Gold standard for osteomyelitis diagnosis

›Periosteal edema and bone marrow signal changes on T2

›Sensitivity approximately 90–100% for osteomyelitis of hand

›Deep space infection delineation when plain film and ultrasound equivocal

›Recurrent or refractory felon not responding to adequate drainage

›MRI limitations

›Not routinely needed for straightforward uncomplicated felon

›Cost, availability, and time limitations in acute setting

›Metallic foreign bodies may be contraindication

CT

›Indications for CT

›Complex cases with suspected deep space involvement

07Disposition/dispo27

Discharge criteria

›Safe for discharge after emergency visit

›Uncomplicated felon — successful bedside incision and drainage performed

›No systemic signs of infection (afebrile, hemodynamically stable)

›Reliable patient with confirmed follow-up in 24–48 hours

›Oral antibiotics prescribed with MRSA coverage

›Return precautions clearly communicated

Observation and admission indications

›Criteria requiring admission

›Systemic signs of infection — fever, tachycardia, leukocytosis

›Immunocompromised host — diabetes, HIV, chemotherapy, chronic steroids

›Concern for deep space infection, flexor tenosynovitis, or osteomyelitis

›Failed outpatient management — refractory or recurrent felon

›IV antibiotics required for source control

Surgical consultation triggers

›Indications for hand surgery consultation

›Kanavel signs present — emergent flexor tenosynovitis consultation

›Suspected osteomyelitis of distal phalanx

›Extensive tissue necrosis or skin loss

›Recurrent or refractory felon after adequate drainage

›Necrotizing soft tissue infection — emergent operative debridement

Transfer criteria

›Transfer to higher level of care

›No on-site hand surgery when operative intervention required

›Necrotizing fasciitis without immediate OR availability

›Septic patient with hand source requiring ICU-level care

Follow-up

›Outpatient follow-up plan

08Treatment/t75

Early felon management (no fluctuance)

›Conservative initial management

›Warm soaks

›20 minutes per session

›3–4 times daily

›Elevation of affected hand above heart level

›Splinting in position of function

›Wrist neutral to 30 degrees extension

›MCP joints 70–90 degrees flexion

›IP joints near full extension

›Empiric oral antibiotics

›TMP-SMX DS one tablet twice daily for MRSA coverage

›Clindamycin 300–450 mg three times daily as alternative

›Duration 7–10 days

›Close follow-up in 24–48 hours mandatory

Incision and drainage — established felon

›Digital nerve block

›Preferred anesthesia approach

›1% or 2% lidocaine without epinephrine (avoid epinephrine in compromised digits)

›Web space block or digital nerve block at base of digit

›Allow 5–10 minutes for full anesthesia before incision

›Incision approach selection

›Superficial abscess — longitudinal volar incision

›Directly over the point of maximal fluctuance

›Avoids neurovascular bundles

›Deep abscess — unilateral mid-lateral incision

›Non-contact (ulnar) side of digit is preferred

›Radial side for thumb and small finger

›Do NOT extend proximal to the DIP flexion crease (risk of flexor tendon sheath violation)

›Avoid hockey stick or fish mouth incisions

›Reserved for very large collections only

›Risk of unstable or painful scar and vascular compromise

›Procedural steps

›Break up septae with blunt hemostat to ensure complete drainage

›Multiple loculations require complete breakdown for cure

›Irrigate the cavity with normal saline

›Loose iodoform gauze wick packing

›Remove packing at 24–48 hours

›Splint in position of function post-procedure

›Tetanus prophylaxis if immunization status not current

Antibiotic therapy

›Empiric oral antibiotic regimens

›TMP-SMX DS (trimethoprim-sulfamethoxazole)

›One double-strength tablet orally twice daily

›MRSA coverage — preferred first-line

›Duration 7–10 days

›Clindamycin

›300–450 mg orally three times daily

›Alternative for TMP-SMX allergy or intolerance

›Duration 7–10 days

›Amoxicillin-clavulanate

›875 mg orally twice daily

›Reserved for bite-related etiology

›Does NOT provide adequate MRSA coverage

›IV antibiotic regimens — severe/complicated

›Vancomycin

›15–20 mg/kg IV every 8–12 hours

›Target AUC/MIC 400–600 (or trough 15–20 mcg/mL by conventional dosing)

›Empiric choice for MRSA coverage in severe infection

›Piperacillin-tazobactam

›3.375 g IV every 6 hours (extended infusion 4 hours)

›Added for polymicrobial concern in diabetics or IV drug users

›Ampicillin-sulbactam

›3 g IV every 6 hours

›Alternative broad-spectrum coverage

Herpetic whitlow management

›Antiviral therapy

›Acyclovir 400 mg orally three times daily for 7–10 days

›Valacyclovir 500 mg twice daily as alternative

›Do NOT incise herpetic whitlow

›Incision causes secondary bacterial superinfection

›Risk of viral dissemination with incision

›Protective dressing to prevent autoinoculation and transmission

Tetanus prophylaxis

›Tetanus assessment

›Update tetanus toxoid if more than 5 years since last booster for contaminated wounds

›Tetanus immunoglobulin (TIG) 250 units IM if unimmunized and contaminated wound

MRSA decolonization

›Decolonization for recurrent MRSA

›Mupirocin nasal ointment 2% applied twice daily for 5 days

›Chlorhexidine body wash daily for 5–7 days

09Special Populations/sp54

Pregnancy

›Anatomic and physiologic considerations

›Increased edema in third trimester may obscure compartment pressure signs

›Lower threshold for imaging and surgical consultation

›Immune modulation in pregnancy may alter presentation

Antibiotic safety in pregnancy

›Preferred antibiotic regimens

›Clindamycin 300–450 mg orally three times daily

›Safe throughout pregnancy (Category B)

›Preferred oral MRSA-active agent in pregnancy

›TMP-SMX — avoid in first trimester (folate antagonism) and near term (kernicterus risk)

›May be used in second trimester if benefit outweighs risk

›Amoxicillin-clavulanate — safe in pregnancy for bite-related infections

›Vancomycin — use with caution; fetal renal monitoring if prolonged use

›Procedural considerations in pregnancy

›Digital nerve block with lidocaine is safe throughout pregnancy

›Avoid epinephrine-containing solutions if vascular compromise concern

›Incision and drainage is the definitive treatment and should not be delayed

Geriatric

›Age-related considerations

›Attenuated febrile response — systemic infection may present without fever

›Leukocytosis and CRP are more reliable markers in elderly

›Peripheral vascular disease common — impaired digital perfusion delays healing

›Polypharmacy and anticoagulation increase procedural bleeding risk

›Antibiotic adjustments in elderly

›TMP-SMX — renal dose adjustment required if eGFR less than 30 mL/min

›TMP-SMX may increase potassium and creatinine in elderly

›Drug interactions with warfarin — increases INR

10Background/b54

Epidemiology

›Incidence and prevalence

›Felons represent a significant proportion of hand infection emergency presentations

›Paronychia and felon together account for a large share of acute hand infections seen in emergency departments

›Thumb and index finger are most commonly affected digits

›MRSA prevalence

›MRSA accounts for approximately 50% of hand infection cultures in urban settings

›MRSA prevalence has increased substantially since early 2000s, necessitating empiric coverage

›Risk population

›Manual laborers, healthcare workers, gardeners at highest occupational risk

›IV drug users have increased risk of polymicrobial and aggressive infection

›Diabetics overrepresented in series requiring operative intervention

Pathophysiology

›Anatomy of the fingertip pulp

›Vertical fibrous septa connect periosteum of distal phalanx to volar skin

›Create 15–20 discrete closed compartments in the volar fat pad

›Infection trapped within these compartments cannot decompress spontaneously

›Consequences of elevated compartment pressure

›Digital compartment syndrome — compression of digital neurovascular bundles

›Ischemic necrosis of the fat pad, skin, or distal phalanx

›Extension to periosteum causes osteomyelitis of distal phalanx

›Microbiology

›Staphylococcus aureus including MRSA — most common pathogen, greater than 75% of cases

›Streptococcus species — less common

›Gram-negative organisms — rare; consider in immunocompromised patients

›Polymicrobial infection — more common in diabetics and IV drug users

›Anaerobes — more common with bite-related inoculation

›Pathogen entry

11Patient Discharge Instructions/pdi29

copy discharge instructions

›Diagnosis and procedure explanation

›You have been diagnosed with a felon, which is an infection of the fingertip pad

›The infected space was opened and drained to release the pus

›Antibiotics have been prescribed to clear the remaining infection

›Wound care instructions

›Keep the wound clean and dry between soaks

›Warm soaks 20 minutes, 3–4 times per day starting after packing removal

›Packing (gauze wick) must be removed at your follow-up appointment in 24–48 hours

›Elevation of the hand above heart level reduces swelling and pain

›Splint or buddy tape as instructed by your emergency physician

›Antibiotic instructions

›Take all antibiotics as prescribed for the full course (7–10 days)

›Do not stop antibiotics early even if the finger looks better

›Take with food to reduce stomach upset

›Follow-up instructions

›Wound check appointment required in 24–48 hours for packing removal

›Culture results may require antibiotic change — follow up with prescribing physician

›Full healing expected within 2–3 weeks after adequate drainage

›Return to emergency department immediately if

›Worsening pain, swelling, or redness despite antibiotics

›Fever or chills developing

›Red streaking running up the arm

›Numbness or color change (pale, blue, or white) of the fingertip

›Pus not improving or increasing after 48 hours

›Swelling spreading to involve the whole finger or the palm

›Activity restrictions

›Avoid manual labor or activities that wet or soil the wound until healing confirmed

12References/r38

Guidelines and key sources

›Gottlieb M, Long B — Management of Finger Felons and Paronychia: A Narrative Review

›Journal of Emergency Medicine 2025

›PMID 40945390

›Comprehensive narrative review of diagnosis and management

›Barger J, Hoyer RW — Fingertip Infections

›Orthopedic Clinics of North America 2024

›PMID 38403372

›Anatomy-based approach to fingertip infection management

›Rerucha CM et al — Acute Hand Infections

›American Family Physician 2019

›PMID 30763047

›Clinical approach including MRSA epidemiology

›Clark DC — Common Acute Hand Infections

›American Family Physician 2003

›PMID 14677662

›Classic review including herpetic whitlow differentiation

›Stevens DL et al — IDSA Practice Guidelines for Skin and Soft Tissue Infections 2014 Update

›Clinical Infectious Diseases 2014

›Evidence-based antibiotic duration and regimen recommendations

›Daum RS et al — Placebo-Controlled Trial of Antibiotics for Smaller Skin Abscesses

›New England Journal of Medicine 2017

›TMP-SMX and clindamycin superior to placebo after incision and drainage

›Malizos KN et al — Infections of Deep Hand and Wrist Compartments

›Microorganisms 2020

›PMID 32503146

›Microbiology and severity stratification for hand infections

›Patel DB et al — Hand Infections: Anatomy, Types and Spread of Infection

Evidence & Review

Evidence & Review