Skin wound—mixed pattern of crush, cut, tear damage to margins (Figure 49.1)

Deep structural injury to bone, tendon, nerve with powerful bites (dog, larger birds, human)

Introduction of oral bacteria to varying depths

Human bites also may transmit HIV, hepatitis B, hepatitis C

Clinical infection depends on burden of microorganisms and capacity of immune system to overcome it (greatest at the skin level, least in a contained synovial space), up to 50% in cat bites, 41% in dog bites.

Risk factors: smoking, immunocompromised status, diabetes, depth of penetration, delay in treatment >24 hours, wound closure⁶

Additional tissue necrosis is proportionate to the duration of infection prior to debridement and spread of infection along anatomic planes (along the course of tendon sheath, from joint cavity into bone)

Sharp penetration to deep target with little structural injury (cats and small dogs)

Crushing (2000 lb/sq in) and avulsion of soft tissue with fracture seen in up to 30% of large dog bites.

Cutting through tendon to bone or joint with impaction fracture (human bites: up to 62% metacarpophalangeal joint penetration and 20% tendon injury).

4.9 million animal bites annually in the United States

Domestic pet bites 2 million/300 000 emergency department visits annually in the United States

80% of animals are known to the victim; 50% are an attempt by the victim to break up animal fight.

Middle-aged Caucasian women (cat bites = 10%-15% of all animal bites)

Wide demographic distribution (dog bites = 80%-90% of all animal bites)