Hand Infections

Basics & Bugs - Setting the Stage

• Anatomy: Pathways of Spread
  • Hand's fascial planes (thenar, midpalmar) & tendon sheaths allow rapid infection spread.
  • Flexor tendon sheaths: Synovial fluid aids bacterial growth; risk of proximal spread to Parona's space.
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• Common Bugs & Considerations:
  • Staphylococcus aureus: Most common. MRSA strains prevalent.

    ⭐ Staphylococcus aureus is the most common pathogen in hand infections.

  • Streptococcus pyogenes: Aggressive, can cause necrotizing fasciitis.
  • Polymicrobial: Frequent in bites (human: Eikenella corrodens; animal: Pasteurella multocida).
• Key Risk Factors:
  • Penetrating trauma (thorns, bites).
  • Diabetes Mellitus (impaired healing/immunity).
  • IV Drug Use (direct inoculation). 📌 IVDU.
  • Immunocompromise (steroids, HIV).

Surface Skirmishes - Skin & Nail Invaders

• Paronychia: Periungual tissue infection.
  • Acute: S. aureus, Streptococci. Tx: Warm soaks, antibiotics. I&D (lift eponychial fold / incise with No. 11 blade).
  • Chronic (>6 wks): Candida albicans, GNBs. Tx: Avoid irritants, antifungals/steroids. Marsupialization.
• Felon: Digital pulp infection (closed septal compartments).
  • Clinical: Throbbing pain, tense swelling.
  • Complications: Osteomyelitis, flexor tenosynovitis, necrosis.
  • Tx: I&D. Incisions: Unilateral longitudinal, hockey-stick.

  ⭐ Transverse incisions for felon drainage are generally contraindicated due to risk of neurovascular injury or flexion contracture.

• Erysipeloid: Caused by Erysipelothrix rhusiopathiae.
  • Source: Occupational: butchers, fish handlers.
  • Clinical: Violaceous, demarcated lesion (fingers/hand).
  • Tx: Penicillin.

Deeper Dangers - Tendons & Spaces

Flexor Tenosynovitis (FTS): Infection of flexor tendon sheath.

• 📌 Kanavel's Signs (FLEX):
  • Finger held in slight Flexion
  • Length of tendon sheath tender (palpation)
  • Enlarged finger (fusiform/symmetrical swelling)
  • Xtension (passive) of finger causes pain
• Pathogens: S. aureus (common), Strep.
• Tx: Urgent IV Abx & surgical drainage (Brunner/mid-axial incisions).

⭐ Kanavel's signs are pathognomonic for flexor tenosynovitis.

Deep Space Infections: Serious; require prompt drainage.

• Thenar Space:
  • Signs: Thumb abducted, swollen & painful thenar eminence.
  • Drainage: Dorsal (1st web) or volar (thenar crease) incision.
• Midpalmar Space:
  • Signs: Loss of palmar concavity, dorsal swelling often present.
  • Drainage: Transverse palmar or longitudinal dorsal incisions.
• Hypothenar Space:
  • Signs: Swelling & tenderness over hypothenar eminence.
  • Drainage: Ulnar border incision (mid-axial).
• Web Space (Collar-Button Abscess):
  • Signs: "Dumbbell" swelling (dorsal & volar), abducted fingers.
  • Drainage: Dorsal & volar longitudinal/zigzag incisions.

Special Ops - Unique Foes & Joints

• Herpetic Whitlow:
  • Viral (HSV). Painful vesicles, digits. Pain out of proportion.
  • Dx: Tzanck smear (multinucleated giant cells).
  • Rx: Acyclovir. AVOID incision & drainage.

  ⭐ Herpetic whitlow should not be surgically incised; can worsen infection or cause secondary bacterial infection.

• Atypical Mycobacterial Infections (e.g., M. marinum):
  • "Fish tank granuloma". Hx: aquatic exposure.
  • Chronic, indolent course; papules, nodules, ulcers.
  • Dx: Biopsy, culture (Löwenstein-Jensen at 30-32°C).
  • Rx: Prolonged multi-drug therapy (e.g., clarithromycin + rifampicin/ethambutol).
• Septic Arthritis (Hand Joints):
  • Causes: Direct inoculation, hematogenous.
  • Dx: Joint aspiration (WBC >50,000/µL, Gram stain, culture).
  • Rx: IV antibiotics, urgent surgical arthrotomy/washout.
• Bite Wounds:
  • Human: Eikenella corrodens.
  • Animal (cat/dog): Pasteurella multocida.
  • Rx: Thorough debridement, irrigation, prophylactic antibiotics (e.g., amoxicillin-clavulanate).

High‑Yield Points - ⚡ Biggest Takeaways

• Kanavel's four cardinal signs are diagnostic for flexor tenosynovitis.
• Staphylococcus aureus is the most common causative organism in most hand infections.
• Paronychia involves the nail fold; felon affects the digital pulp.
• Herpetic whitlow is a viral infection (HSV); avoid incision and drainage.
• Human bites (fight bites) are high-risk for polymicrobial infections including Eikenella corrodens; require aggressive treatment.
• Deep space infections (e.g., thenar, midpalmar) necessitate prompt surgical drainage.