Human Bite

Aka: Human Bite, Clenched-fist Injury, Clenched-Fist Bite Wound, Fight Bite, Tooth-Knuckle Injury

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II. Epidemiology

  1. Incidence: 250,000 Human Bites per year in U.S.
  2. Most commonly seen in young adult males (teenagers and early 20s), including "Fight Bites"

III. Pathophysiology

  1. Delayed presentation is common (wound appears mild initially)

IV. Mechanism: Hand is often injured in fist fight

  1. Known as Clenched-Fist Bite Wound or Fight Bite
  2. Index or Long finger MCP joint strikes tooth (typically upper teeth)
    1. Site of injury obscured in extension
    2. High risk for infection spread
    3. Often associated with small (3-5 mm) Laceration over MCP joint
  3. Associated injuries (in 75-100% of cases) despite initial benign, superficial appearance
    1. Penetrated tendon
    2. MCP joint capsule penetration
    3. Metacarpal head
    4. Extensor Tendon Injury
    5. Patzakis (1987) Clin Orthop Relat Res (220): 237-40 +PMID:3594996 [PubMed]

V. Types

  1. Occlusive Bites
    1. Teeth penetrate and sink into skin, often on an extremity
    2. Seen more often in women
  2. Closed Fist (Fight Bite) - most common
    1. Laceration from fist contacting teeth
    2. Seen more often in men

VI. Risk Factors

  1. Fight Bites
    1. Young males
    2. Alcohol Intoxication
  2. Human Bites
    1. Assailants with psychiatric Illness or Developmental Delay
    2. Health care workers
    3. Law enforcement

VII. Causes: Organisms

  1. Most common pathogens
    1. Eikenella corrodens (anaerobic Gram Negative Rod)
    2. Streptococcus Pyogenes
  2. Other common aerobic Bacteria
    1. Staphylococcus aureus
    2. Streptococcus
  3. Other common Anaerobic Bacteria
    1. Typically mixed Anaerobes and aerobes
    2. Bacteroides
    3. Fusobacterium
    4. Prevotella
    5. Peptostreptococcus
  4. Rare, but case reports
    1. HIV Infection
    2. Hepatitis B Infection
    3. Hepatitis C Infection
    4. Syphilis
    5. Herpes Simplex Virus

VIII. Signs: Fight Bite

  1. Laceration of 3-5 mm overlying the MCP joint, and less commonly, the (PIP joint)
  2. Third metacarpophalangeal joint (MCP) on dominant hand is most commonly affected
    1. Tendon retracts proximally with relaxation of hand, tracking infection to deeper tissue

IX. Exam

  1. Thorough inspection
    1. Neurovascular evaluation
    2. Extensor tendon function (Elson Extensor Tendon Test)
  2. Cleansing and Debridement is critical
  3. Extend Laceration as needed for full visualize

X. Labs

  1. Anaerobic and aerobic cultures from wound
  2. Wound Gram Stain

XI. Imaging: Clenched-Fist Bite Wound

  1. Finger XRay
    1. Fracture
    2. Osteomyelitis
    3. Foreign body

XII. Management

  1. Hand surgeon Consultation (Fight Bite)
    1. Discuss with local hand surgery
    2. Protocols vary by locale and per individual consultant
    3. Some experts recommend immediate admission, Debridement, irrigation and ParenteralAntibiotics
  2. Tetanus Prophylaxis
  3. Hepatitis B Postexposure Prophylaxis
    1. Hepatitis B transmission has occurred with Human Bites (albeit rare)
    2. Prophylaxis Indicated if patient unimmunized and source cannot be tested or is suspected positive for Hepatitis B
      1. See Hepatitis B Postexposure Prophylaxis
      2. Give Hepatitis B immune globulin and Hepatitis B Vaccine
  4. Other Postexposure Prophylaxis
    1. HIV and Hepatitis C transmission are more rare than Hepatitis B transmission
    2. Transmission is possible if blood is in biter's Saliva
    3. Consider Infectious Disease Consultation regarding HIV Postexposure Prophylaxis indications
  5. Wound left open, and no structures are repaired
  6. Extensively irrigate wound
  7. Explore and debride wound under adequate lighting and exposure
    1. Extend Puncture Wounds in distal to proximal plane
    2. Remove foreign bodies
  8. Wick may be placed in wound, and removed the next day
  9. Splint hand in a position of function
  10. Apply Soft Bulky Dressing
  11. Antibiotics
    1. Precautions
      1. Obtain wound tissue for Gram Stain and culture prikor to Antibiotics if possible
      2. Infections are most often polymicrobial
    2. Oral agents
      1. Amoxicillin-clavulanate (Augmentin) or
      2. Dicloxacillin with Penicillin (covers E. corrodens)
      3. Cephalexin (Keflex) with Penicillin or
      4. Clindamycin with Fluoroquinolone or
      5. Clindamycin with Trimethoprim-sulfamethoxazole
    3. Parenteral agents
      1. Indications
        1. Consider 1 Parenteral dose and then oral
        2. Diabetes Mellitus
        3. Peripheral Vascular Disease
        4. Immunocompromised patient
        5. Wound older then 24 hours
        6. Signs of extensor tendon, capsule, or bone injury
        7. Systemic symptoms
        8. Concurrent Cellulitis
      2. Agents
        1. Ampicillin-sulbactam (Unasyn)
        2. Ticarcillin-clavulanate (Timentin)
        3. Cefoxitin (Mefoxin)
  12. Daily Wound Cleansing and dressing changes
    1. if satisfactory healing:
      1. Antibiotics for 2-3 weeks
    2. if not improving then:
      1. Additional surgical Debridement
      2. Consider IV Antibiotics
    3. Complete Extensor Tendon Laceration
      1. Requires secondary repair
      2. Otherwise Secondary wound closure is not necessary
  13. Outpatient Management Indications
    1. Indicated for wounds less than 24 hours old and no signs of infection
  14. Hospital management Indications
    1. Delayed presentation >24 hours after wound onset
    2. Immunocompromised state
    3. Systemic symptoms
    4. Joint capsule penetration

XIII. References

  1. Cowling and House (2017) Crit Dec Emerg Med 31(5): 15-20
  2. Hori (2015) Crit Dec Emerg Med 29(3): 2-7
  3. Clark (2003) Am Fam Physician 68:2167-76 [PubMed]
  4. Presutti (1997) Postgrad Med 101(4): 243-54 [PubMed]

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