Larry Mellick, MD, MS, FAAP, FACEP
Professor of Emergency Medicine and Pediatrics
Medical College of Georgia
Pearl: Human bite injuries can be a diagnostic challenge when the history is lacking or distorted. Don’t miss the “fight bite” and be able to answer the “who or what did it” question.
Presentation 1: A 13-year-old boy was involved in an altercation with a 12-year-old and sustained a laceration to his hand from the teeth of his opponent. The patient told his mother that he fell off his skate board. Later, as the pain and swelling worsened, he confessed what actually happened. Unfortunately, he also had fractures of the 4th and 5th metacarpals (qualifying him as having open fractures). (Figure 1, Figure 2, Figure 3, Figure 4.) He was treated with intravenous clindamycin and admitted to the hand service, where the fractures were reduced and stabilized.
Presentation 2: A toddler presented to the emergency department with his parents for evaluation of an alleged bite to his forearm. The parents wanted to know if the bite was caused by another child. The bite measured 2.1 cm in diameter. (See Figure 5.)
Discussion: Fight Bites: “Fight bites” are notorious because of the story fabrication sometimes associated with them and their propensity for infection. In fact, any time a patient (typically male) presents with a laceration over the metacarpophalageal joints, specifically ask the patient about whether the injury occurred during an altercation. Simultaneously, in older patients, get close enough to smell their breath for any evidence of recent alcohol ingestion that may have been a contributing factor.
Animal, Child, or Adult? When there is a suspicious bruise on a child’s body that appears to be consistent with a human bite, two questions are commonly asked. The first is whether the occlusal injury was inflicted by an animal or a human. The second is whether it was caused by an adult or child.
In contrast to dog bite marks, human bites usually are superficial abrasions or contusions.1 Additionally, humans have four incisors in each dental arch and short canines. The marks left by incisor teeth tend to be rectangular, and the canine teeth usually leave triangular marks. In contrast, dogs have six incisors and long, curved canines that can leave deep punctures as well as torn tissue. The arch of the human mouth is elliptical or oval, while dogs have a long arch with a short, straight anterior segment. Consequently, the bite configuration is not oval.2
If the bite appears to be consistent with a human bite, the question typically asked by child protective services is whether the bite was caused by an adult or a child. In general, the most common guidelines are that the normal intercanine distance of an adult is 2.5-4.0 cm.3 Any human bite marks with an intercanine distance more than 3.0 cm is most likely inflicted by an adult.4 Unfortunately, dynamic distortion at the time of the bite and tissue distortion do occur and should cause some degree of uncertainty to linger.5,6