Felon

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Background

  • Subcutaneous pyogenic infection of the pulp space compartments of the distal finger
  • Do not mistake for pulp erythema due to paronychia or herpetic whitlow
  • Infection typically begins with minor trauma to dermis overlying finger pad (e.g. foreign body such as a splinter)
    • May spread to flexor tendon sheath, IP joint, or underlying periosteum

Nailtip Anatomy

A. Nail plate; B. lunula; C. root; D. sinus; E. matrix; F. nail bed; G. hyponychium; H. free margin.
  • The perinychium includes the nail, the nailbed, and the surrounding tissue.
  • The paronychia is the lateral nail folds
  • The hyponychium is the palmar surface skin distal to the nail.
  • The lunula is that white semi-moon shaped proximal portion of the nail.
  • The sterile matrix is deep to the nail, adheres to it and is distal to the lunule.
  • The germinal portion is proximal to the matrix and is responsible for nail growth.
Felon

Clinical Features

  • Red, tense, and markedly painful distal pulp space
    • May see necrotic appearing tissue distally due to increased pressure in space

Differential Diagnosis

Hand and finger infections

Evaluation

Workup

  • X-ray to assess for foreign body
  • Ultrasound can be utilized by placing the hand in a bowl of water and holding high frequency linear probe a few cm away from the finger (water is an excellent conductor)
  • Gram stain and culture (chronic infections may be caused by atypical organisms)

Evaluation

  • Usually a clinical diagnosis

Management

Incision and drainage

Incision of felon.
  • Perform digital block
  • The incision should be made along the ulnar aspect of the index, middle, and ring fingers and along the radial aspects of the thumb and little finger.
  • Number 11 blade is used to make incision on nonoppositional side of affected digit. Digital arteries and nerves arborize near the distal interphalengeal joint, minimizing risk of significant neurovascular damage.
  • Start incision 5 mm distal to flexor DIP crease
  • End incision 5mm proximal to nail plate border
  • Bluntly dissect and explore wound until abscess is decompressed

no need for packing

  • DO NOT perform a "fishmouth" incision since this may results in: Unstable finger pad, neuroma, and/or loss of sensation

Antibiotics

Indicated for felon associated with cellulitis Definitive treatment is drainage but antibiotic coverage for S. aureus and Strep with caution to identify Herpetic whitlow

Disposition

  • Discharge with follow-up in 2 days for wound check
  • Refer to hand surgery only if systemically ill or concern for complicated infection
  • Instruct patient to keep extremity elevated

See Also

References