Felon

Aka: Felon, Finger Pulp Abscess, Whitlow

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II. Definitions

  1. Felon (Finger Pulp Abscess, Whitlow)
    1. Infection of closed space of distal phalanx pulp

III. Pathophysiology

  1. Infection contained within compartment walled by the fibrous septae of the finger pulp

IV. Causes

  1. Staphyococcus aureus
  2. Streptococcus species

V. Mechanism: Local finger tip Puncture Wound

  1. Splinter
  2. Glass fragment
  3. Punctures (e.g. Finger-stick Blood Sugar testing)

VI. Symptoms

  1. Rapidly increasing pressure and pain at finger tip
  2. Thumb and index finger most commonly affected

VII. Signs

  1. Tense, swollen and erythematous of the finger pad (pulp)

VIII. Differential Diagnosis

  1. Paronychia
  2. Herpetic Whitlow
  3. Cellulitis
  4. Tuft Fracture

IX. Imaging

  1. Bedside Ultrasound
    1. May demonstrate fluid collection within pulp
  2. Finger XRay
    1. Indicated if suspected retained Radiopaque Foreign Body

X. Complications

  1. Osteomyelitis of distal phalanx
  2. Tissue necrosis of finger pulp
  3. Contiguous spread
    1. Pyogenic Flexor Tenosynovitis
    2. Does not typically spread to adjacent DIP joint (infection typically contained within fibrous septae)

XI. Management: Conservative measures

  1. Tetanus Prophylaxis
  2. Warm soaks
  3. Elevate the hand
  4. Antibiotics for 7 to 10 days (not typically needed for isolated abscess AFTER Incision and Drainage)
    1. Cephalexin (Keflex)
    2. Dicloxacillin
    3. Trimethoprim-Sulfamethoxazole
    4. Amoxicillin-Clavulanate (Augmentin)
    5. Clindamycin

XII. Management: Early Incision and Drainage

  1. Indications
    1. Clear abscess pocket identified
    2. No improvement after 24 hours conservative therapy with Antibiotics
  2. Contraindications
    1. Herpetic Whitlow
  3. Anesthesia
    1. Digital Block (Metacarpal Block)
  4. Technique
    1. Apply Tourniquet at base of finger
    2. Needle aspiration may be used as an alternative to scalpel incision
      1. Needle aspiration may also be used to localize the abscess pocket for Incision and Drainage
    3. Identify point of maximal tenderness and swelling
      1. Make 5-10 mm incision using method below
      2. Insert to depth that decompresses the abscess (but avoid the underlying bone)
      3. May massage the area to express purulent discharge through the incision
    4. No specific point of tenderness
      1. Make straight single volar (superficial abscess) or high lateral incision (deep abscess)
        1. Start incision at least 5 mm distal to DIP joint (avoids tendons)
        2. Keep lateral incision within 5 mm of nail border
        3. Continue incision distally to distal phalanx tip
        4. Thumb and pinky finger: Incise radial side
        5. Index, long and ring fingers: Incise ulnar side
      2. Avoid incision methods with higher risk of scar
        1. Transverse palmar incision
        2. J-shaped incision, Fish mouth incision or Hockey Stick incision
    5. Wound exploration
      1. Gently open subcutaneous tissue with hemostat
      2. Irrigate wound
      3. Pack with sterile gauze for 48 hours
  5. Complications
    1. Painful neuroma
    2. Finger pad instability
    3. Scarring

XIII. Follow-up care

  1. Splint and elevate for 48 hours
  2. Saline soaks twice daily
  3. Maintain range of motion
  4. Anticipate healing in 2 weeks

XIV. References

  1. Warrington (2024) Crit Dec Emerg Med 38(8): 18-9
  2. Clark (2003) Am Fam Physician 68:2167-76 [PubMed]

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