Causes / typical injury mechanism: Human bites on the hands can occur as self-inflicted wounds, as accidents, or as a result of violence. The most severe human bites typically occur as "fight bites," with clenched fist injuries in which the patient's metacarpophalangeal (MCP) joint makes contact with someone's teeth.

Classic history and presentation: Human bites tend to cause compressive tissue damage without tissue avulsion. They are typically small and can therefore easily be missed upon initial examination.

Prevalence: Human bites account for approximately 2%-3% of bites on the hands. The fight bite mechanism is more common in male patients with a median age of 28 years. Occlusive bite wounds occur more frequently overall, and these bites show no difference in frequency between male patients and female patients.

Risk factors: Risk factors for infectious sequelae include a visibly dirty wound, delayed presentation for medical treatment, additional bite wounds, an immunocompromised state, and a history of diabetes, asplenia, or peripheral vascular disease. It is also important to consider the health status of the person who bit the patient, including their various medical comorbidities and chronic infectious diseases, such as hepatitis B, hepatitis C, and HIV. Bites from children tend to have lower infection rates, likely due to decreased bacterial oral flora.

Pathophysiology: The poor vasculature in the superficial structures of the hands leads to an increased risk of infectious spread. In clenched fist injuries, the MCP joint is positioned prominently and teeth can penetrate the extensor compartment because of the minimal soft tissue coverage, leading to tendon, cartilage, and bone damage. As the hand relaxes, the injured structures retract from view and create a sealed environment that is conducive to bacterial growth. Bacteria can then easily spread along the bones, tendons, and ligaments. Cellulitis, abscess formation, septic arthritis, and osteomyelitis are potential sequelae. Infectious symptoms may occur within 12 hours of the bite injury, so prompt treatment is necessary to prevent future morbidity.

Related topic: animal bite infection