Key points

Introduction

The human face is a cosmetically and overly sensitive area, which is a critical component in our daily human interactions with others. Trauma to the facial tissues has immense social, psychological, and functional ramifications. Human and animal bites to the face tend to result predominantly in isolated soft tissue injury, but this soft tissue injury wound tends to be ragged and more prone to unfavorable scarring. The oral flora of the animal that inflicts the bite or bites is a factor and has implications for management. Most animal bites sustained by humans occur to the extremities, with less than 20% involving the face. Dogs and to a lesser extent cats tend to be the most frequently involved animal in delivering the bite to humans in the developed world, but other animals, such as monkeys, horses, camels, bears, wild boars, rodents, sheep, pigs, snakes, fish, and crocodiles, have been documented in biting humans. The importance of this is that each animal has a characteristic tooth shape and format that ultimately has an influence on the degree and type of injury. Each species of animal has a relatively unique oral microbacterial flora, which has implications for the potential infection risk and the management of a wound. Following dogs and cats, humans tend to be the third most common source of a bite injury to a fellow human. Unlike the above listed animals, a human bite has the potential to be used to identify the aggressor based on forensic dentistry.

Epidemiology

With regards to public health, an estimated 2% of the population is bitten each year. Animal bites are more prevalent in men and boys. With regards to cat and dog bites, there tends to be a sex predilection with regards to the human that sustains the bite injury. Women and girls are most likely to be bitten by cats, whereas men and boys tend to be bitten mostly by dogs. Dogs account for most facial bite wound injuries. The age of the human victim is also a factor to consider. Animal bites to the face are far more common in children than adults, with approximately 10% of bites involving the head and neck in adults compared with approximately 75% in children. The reasoning behind this is that children tend to have less well-developed motor skills with which to defend themselves with their extremities. Children also tend to have larger heads with respect to their bodies, consequently making it a larger target. Last, children are less likely to be able to recognize the emotional behavior of animals, and as a result, do not appreciate the danger and may be more prone to provoking the animal.

Wound characteristics and classification

Bite wounds tend to result in 3 broad categories of injury: puncture wounds, lacerations, and tissue avulsion injuries. Dog bites tend to result in more lacerations and avulsive-type injuries. Dog bite wounds are generally ragged and can have a component of crush injury. The breed of dog inflicting the injury also has an effect on the resulting wound. Pit bulls, terriers, and rottweilers tend to result in more ragged and avulsive injuries because of their dental arrangement. These dogs also tend to have a more forceful bite, with some estimating the potential bite force to be up to 450 pounds per square inch. A retrospective analysis of facial dog bites at a US trauma center showed bite wounds of some breeds of dogs were generally managed with direct repair, but other breeds, such as those noted above, tended to require reconstruction as part of the management of the dog bite injury. This force is potentially strong enough to cause fractures of the human skeleton, especially in a child, and has the potential to cause death if inflicted on the skull. Dog bite injuries inflicted on the neck can be particularly serious, as airway damage with subsequent asphyxiation or great vessel injury with subsequent exsanguination is possible. Dog bites of the face tend to involve lips, nose, and cheek anatomic areas. Cat bites tend to be more puncture-type wounds. Cat bites tend to have a higher incidence of infection because of the penetrating nature of the injury and the microbiology of the cat oral cavity. Human bites to the face more commonly involve the ear, but the lip and nose also are sites with a higher incidence of human bite injury. To aid communication and to allow better assessment of outcomes with respect to varying facial bite wound injuries, Lackmann and colleagues introduced a classification based on facial dog bit wound injuries in children, as shown in Table 1 . The severity of bite wounds should be assessed, and a determination should be made if the bite wound is a high-risk bite wound. High-risk bite wounds generally require more urgent attention and have the potential to lead to significant complications. High-risk bite wounds include full-thickness puncture wounds, severe crush injury accompanying the bite injury, cat bite wounds, and bite wounds that involve bone, joint, tendon, and/or ligament. Facial bite wounds in of themselves are generally considered high risk without any of the above features though.

Microbiology

The microbiology of animal bite wounds is polymicrobial. This polymicrobial wound environment is composed of a broad mixture of aerobic and anaerobic organisms. Commonly involved aerobic species include Neisseria , Corynebacterium , and Staphylococcus . Anaerobes most frequently implicated in animal bite wounds include Fusobacterium , Bacteroides , Prevotella , Propionibacterium , Peptostreptococcus , and Porphyromonas .

Focusing on the specifics of dog and cat bites, Pasteurella species, which is a gram-negative aerobic species and present in the oropharynx of most dogs and cats, is frequently implicated in dog and cat bite wound infections. Pasteurella canis is found in 50% of dog bite wounds. Pasteurella multocida is found in approximately 30% of dog bite wounds and in approximately 50% of cat bite wounds. Pasteurella species bite wound infection can cause cellulitis in humans if not managed appropriately, and this can progress to purulent discharge, fever, osteomyelitis, septic arthritis, and ultimately, septicemia with its consequences if left unchecked.

Human bite wounds also tend to be polymicrobial. Eikenella corrodens , which is a normal commensal of the human oral cavity, appears to be particularly prevalent with respect to human bite wound infections. Viridans streptococci and Streptococcus anginosus tend to be relatively prevalent in human bite wound infections. In general, the aerobic and anaerobic organisms found in dog and cat bites tend to be otherwise similar in human bites with the exception of the Pasteurella species. A more worrisome point to consider with human bite injuries is the possibility of hepatitis B, hepatitis C, and HIV infection. These infections can be transferred from the human delivering the bite to the victim, especially if gingival trauma occurs to the person delivering the bite with resultant release of their blood, which can gain access to the victim. Consideration has to be given in human bite wound injuries for the potential of these microorganisms infecting the victim.

With animal bite wounds, the potential for rabies must be considered. Postexposure prophylaxis for rabies is essential and can prevent rabies in humans, which is currently untreatable. Postexposure prophylaxis consists of local wound treatment with washouts and cleaning of the wound followed by vaccination. Consideration should be given to the administration of rabies immune globulin dependingt on the type of exposure and the suspicion for being bitten by an animal suffering from rabies. The use of vaccination in conjunction with rabies immune globulin is essentially 100% effective in preventing human infection if inoculated by a bite from a rabies virus effected animal.

Evaluation

Initial evaluation should focus on the principles of Advanced Trauma and Life Support (ATLS). Establishment of a defined airway and control of any hemorrhage are of particular importance and are relevant in pediatric patients. As part of the secondary survey, evaluation should be performed for any penetrating intracranial injuries that may result in a pediatric patient owing to their relatively less mineralized calvarial bones. Neurologic function should be assessed. With regards to the face, particular reference to facial nerve function and the sensory nerve function should also be evaluated and documented.

History and physical examination are of primary importance. As part of the history, documentation should be made of the timeline since the bite injury occurred. Ideally, patients with bite injuries to the face should be seen as soon as possible given that early management of the injury reduces the likelihood of infection. Bite injuries seen within 6 hours and managed appropriately have a lower risk of wound infection compared with those seen in a delayed fashion. Animal bite wounds to the extremities are generally left open to reduce the risk of infection. With regards to the face, this is generally avoided to minimize the cosmetic impact of the injury. Bite wounds of the face seen and treated up to 48 hours after the injury with suturing have an acceptably low risk of infection but benefit from potential cosmetic benefits of suturing. There are advocates for suturing closed facial bite wounds presenting in a delayed fashion 48 hours or more after the injury. On review of the patient’s past medical history, one should pay particular attention to any conditions that may indicate an immunocompromised patient. Specific questions regarding the presence of diabetes, excessive alcohol consumption, a patient who is a transplant recipient, or a patient taking immunosuppressive drugs for autoimmune conditions should be elicited. The patient should be questioned on the use of tobacco with particular reference to smoking tobacco. This risk factor predisposes the patient to poor healing and an increased risk of infection.

As part of the clinical examination, any signs of infection should be documented, including but not limited to erythema, purulent drainage, or systemic signs of infection. With regards to the perioral and periorbital tissues, a clear description of the wound should be placed in the medical record. Any avulsed tissue should be noted with an accurately measured wound defect size obtained for the medical records. Medical photography can be invaluable in recording the injury. Injuries involving the perioral and periorbital tissues are high-risk injuries and put the patient at significant risk of cosmetic and functional impairment. Photodocumentation can also be very important in animal and human bite injuries, as these cases often have litigation consequences.

To aid proper assessment of the wound, any dried coagulation tissue or foreign body should ideally be removed with gentle saline irrigation. Excessive scrubbing should be avoided as part of the initial examination. To complete the examination, consideration should be given to radiological investigation. If there is any suspicion for fracture of the facial skeleton, strong consideration should be given to computed tomographic examination. If there is a concern for foreign body within the soft tissue, plain films may be suitable. Once a complete clinical, and if relevant, radiological examination, is completed, a discussion should be had with the patient with regards to their potential treatment options.