Dogs are the animal most frequently implicated in causing bite injuries to the human face. Dog bite injuries are most prevalent in younger patients. Pasteurella species are commensals of the oral microbiome of dogs and cats and are frequently implicated in infections resulting from dog and cat bite injuries. HIV, hepatitis B, and hepatitis C need to be considered in bites inflicted by humans. All animal bite wounds should be washed out. Most animal bite injuries can be managed in an outpatient setting. Given the cosmetically sensitive nature of the face, bite wounds generally merit suturing, even in delayed presentations.
Dog bites are the most common facial animal bites.
These wounds have a significant infection potential.
The management includes not only surgical but also medical management.
Management of animal and human bites is individualized based on each case.
Dogs are the animal most frequently implicated in causing bite injuries to the human face.
The oral flora of the animal that inflicts the bite or bites is a factor and has implications for management.
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.
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.
Cat bites tend to be more puncture-type wounds.
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.
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.
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.
|I||Superficial injury without muscle involvement|
|IIA||Deep injury with muscle involvement|
|IIB||Full-thickness injury of the cheek or lip with oral mucosal involvement|
|IIIA||Deep injury with tissue defect|
|IIIB||Deep avulsive injury exposing nasal or auricular cartilage|
|IVA||Deep injury with severed facial nerve and/or parotid duct|
|IVB||Deep injury with concomitant bone fracture|
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.
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.
All bite wound injuries should at least be irrigated with normal saline. There is minimal to no extra benefit in the addition of povidone iodine or hydrogen peroxide. Pulsed lavage also does not seem to be merited in most animal bite wound infections to the human face. Given the importance of facial cosmesis, facial bite wounds merit primarily closure with suturing if possible. In the process of primary closure, placement of deep sutures should be used judiciously, as these can act as a potential nidus for infection. A monofilament nonabsorbable suture is preferable for skin reapproximation. The facial tissues have an abundant arterial supply; thus, minimal excision and debridement of tissue should be performed. If tissue is severely damaged and likely necrotic because of a crush injury or loss of vascularity, this should be removed, as it can act as a nidus for infection. An alternative strategy is minimal debridement and monitoring the wound with packing and repeated washouts and debridements until the treating provider is satisfied all necrotic material is removed before proceeding with closure/reconstruction of the wounds. Unfortunately, this management strategy is likely to have increased scarring, which ultimately is cosmetically detrimental.
Avulsive wounds with tissue loss require consideration for closure by secondary intention, local tissue rearrangement, skin grafting, or free tissue transfer depending on the size and the location of the defect. Cosmetically and functionally sensitive areas, such as the perioral tissues and periorbital tissues, require careful evaluation. Local rearrangement of tissue with advancement of mucosa and the skin of the lip may be sufficient to allow a cosmetic and functional result if orbicularis oris is intact ( Fig. 1 ). With some avulsive lip injuries, consideration can be given to reimplanting the avulsed tissue if the patient is seen quickly following the injury ( Fig. 2 ). This strategy is risky, and complete loss of the replaced avulsed tissue can occur frequently. Generally, if orbicularis oris is not intact, wedge resection with primary closure across the defect versus an Abbe or an Estlander flap may need to be considered ( Fig. 3 ). Larger defects may require reconstruction with advancement flaps, like Fernandes, Bernard, or Karapandzic flaps. Complete loss of the lip will require free tissue transfer. With regards to the periorbital tissues, assessment of lacrimal system should be performed. Any defects in the lacrimal system require dacryocystorhinostomy. Reconstruction to allow functional return of the sphincter mechanism of the periorbital and perioral tissues is of prime importance. Without return of the sphincter function, long-lasting and severe functional and cosmetic impediment will be the result.