Human Bites 

Updated: Mar 04, 2021
Author: Jeffrey Barrett, MD; Chief Editor: John L Brusch, MD, FACP 

Overview

Background

Approximately 10%-15% of human bite wounds become infected owing to multiple factors. The bacterial inoculum of human bite wounds contains as many as 100 million organisms per milliliter and is made up of as many as 190 different species. Many of these are anaerobes that flourish in the low redox environment of tartar that lies between human teeth or in areas of gingivitis. Most injuries due to human bites involve the hands. Hand wounds, regardless of the etiology, have a higher rate of infection than do those in other a locations. 

Infections associated with human bites are often far advanced by the time they receive appropriate care. Patients often wait until infection is well established before seeking medical treatment. These wounds are frequently more extensive than estimated on initial examination by the inexperienced observer and are frequently managed inadequately. 

Human bites have been shown to transmit hepatitis B, hepatitis C, herpes simplex virus (HSV), syphilis, tuberculosis, actinomycosis, and tetanus.

Evidence suggests transmission of human immunodeficiency virus (HIV) through human bites is possible but very unlikely. 

The goals of therapy are to minimize possible soft tissue deformity and to prevent or appropriately treat infection. Recognition of the high risk of infectious complications and early aggressive treatment are mandatory to prevent serious wound infection and its associated complications.[1, 2]  

Pathophysiology

Human bite wounds occur as 2 separate entities: clenched-fist injuries and occlusive bites.

Clenched-fist injury

Clenched-fist injuries are the most common and have the greater clinical significance. They occur as the closed fist strikes the teeth of another individual with sufficient force to create a small wound, usually 3-8 mm in length. The injury usually occurs over the dorsal surface of the third and fourth metacarpophalangeal (MCP) or proximal interphalangeal joints of the dominant hand. Because of the thinness of the skin in these areas, potential injuries include joint penetration, metacarpal fracture, and extensor tendon laceration. Injury to the digital nerve or artery is rare.

As the fingers extend following injury, the bacterial inoculum may be carried proximally with the extensor tendons. This makes adequate irrigation of the wound more difficult. These are the most serious human bite wounds, and they require the most aggressive treatment.

Occlusive bites

Occlusive bites occur when there is sufficient force to break the skin. Such injuries to the hand have a higher infection rate than similar bites to other parts of the body because of the thinness of the skin in this area.

When a finger is bitten, such as in a chomping-type injury, tendons and their overlying sheaths are in close proximity to the skin. The wound may appear to be a minor abrasion-type injury, but careful inspection is required to rule out deep injury.

Occlusive human bite wounds of the head and neck result in avulsion, laceration, and crushing of the tissues. Even so, when a tooth strikes the head, even a deep puncture wound may appear innocuous. However, deep, subgaleal, bacterial contamination is possible. This is especially true in young children who have relatively thin, soft scalp and forehead tissue.

Disease transmission

Regardless of the mechanism and anatomic location of the bite wound, the composition of the bacterial inoculum is the same. Cultures of human bite wounds are commonly polymicrobial in nature, and aerobes and anaerobes are represented almost equally. Beta-lactamase production occurs frequently. Commonly isolated aerobes include Eikenella corrodens and Staphylococcus, Streptococcus, and Corynebacterium species. Staphylococcus aureus is isolated in up to 30% of infected human bite wounds and is associated with some of the most severe infections.

E corrodens is a slow-growing, facultative, anaerobic, gram-negative bacillus. It is frequently associated with chronic infection and abscess formation. This pathogen is isolated in 30% of human bite wounds. Other commonly isolated anaerobes include Bacteroides, Fusobacteria, Prevotella, and Peptostreptococcus species.

In addition to the acute risk of localized infection, human bites pose the potential for the transmission of systemic infections, which can be life threatening. Hepatitis B transmission via human bites is well documented. In approximately 75% of patients with hepatitis B, the antigen is detectable in their saliva, and it is approximately 100 times more infectious than HIV.

Less likely is the transmission of HIV, although several cases of likely transmission through bites have been documented.[3, 4, 5] HIV is found in the saliva of affected patients, although at lower levels than in the blood. In addition, salivary inhibitors render the virus noninfective in most cases[6] .  Neverthless, in severe wounds it may be reasonable to provide post-exposure prophylaxis to patients if the source of the bite is HIV positive[7] .

Etiology

[5] The causes of human bite wounds include the following:

  • Aggressive behavior, often in combination with alcohol (the cause of most clenched-fist injuries)

  • Rough sexual play or sexual assault

  • Domestic violence

  • Child abuse

  • Occupational injury to dental personnel

  • Seizure-related tongue lacerations

  • Nose biting (punishment for adultery in several cultures)[8]

  • Accidents during sporting events

  • Aggressive play of children in daycare centers

  • Self-inflicted wounds in persons who are emotionally disturbed or mentally handicapped - Lesch-Nyhan syndrome is an uncommon disorder that includes self-mutilation through biting

Institutionalized patients with poor impulse control create a high-risk environment for human bite wounds.

Epidemiology

Occurrence in the United States

Human bites are ranked as the third leading cause of all bites seen in hospital emergency departments (after dog and cat bites), accounting for 3.6-23% of bite wounds; however, the true frequency is difficult to estimate because most human bites are probably unreported or patients fail to seek medical attention. Of those reported, approximately 60% occur in an upper extremity (most frequently the dominant one), while 15% occur in the head and neck region, most commonly the ears, nose, or lips. The remainder occur on the breasts, genitals, thighs, and other areas.

International occurrence

In a 4-year retrospective review in the United Kingdom, 421 (13%) human bites were identified out of 3136 case notes. The majority of those bitten were young males, with 44% of the males aged 16-25 years. The male-to-female ratio was 3:1.[9]

Sex- and age-related demographics

Clenched-fist infections are predominantly found in men, presumably owing to their more aggressive behavior. Occlusive bite wounds occur with equal frequency in males and females.

The peak incidence of human bites, including occlusive bites and clenched-fist injuries, occurs in individuals aged 10-34 years.

Prognosis

The prognosis is excellent in patients who promptly seek medical attention following injury;however, patients frequently present days to weeks after injury, when the infectious process is well established. Conversely, the severity of a human bite injury may initially be underestimated, especially by an inexperienced observer, resulting in a significant delay of appropriate therapy.

Morbidity of human bites is primarily related to the degree of permanent function and/or cosmetic impairment.

Bite infections of poorly vascularized structures, such as ear cartilage, are particularly difficult to cure. In particular, in ear infections, plastic surgery is often needed to achieve an acceptable cosmetic result.

The morbidity of human bites is also related to infection and its sequelae. Prior to the era of antibiotics, up to 20% of hand bites required amputation of a finger. While amputation is seldom required today, residual scarring may result in permanent functional and/or cosmetic impairment; complications include the following:

  • Cosmetic deformity resulting from wound contraction

  • Permanent hand disability secondary to stiffness and/or chronic pain

  • Infectious tenosynovitis

  • Septic arthritist,

  • Abscess formation

  • Amputation (rare)

  • Transmission of disease (eg, hepatitis B or C, HIV)[4]

  • Osteomyelitis

  • Necrotizing fasciitis

  • Joint infections[10]

Occlusive bite injuries among toddlers placed in crowded daycare centers are usually superficial and rarely become infected.

Patient Education

Patients must clearly understand the signs and symptoms of wound infection that signal a need to return for immediate reevaluation. These include, but are not limited to, the following:

  • Fever

  • Odor

  • Drainage

  • Purulence

  • Swelling

  • Cellulitis

  • Warmth

  • Pain

  • Decreased mobility

Patients must also clearly understand the importance of early and regular follow-up care for this seemingly minor injury, as well as the rationale for providing antibiotics and the importance of compliance with this recommendation.

Moreover, patients need to be informed of potential complications that may develop even with complete compliance with the care plan, and they should understand that wound revision for cosmetic or functional purposes may be desirable at a later date.

For patient education information, see the First Aid and Injuries Center and the Infections Center, as well as Human Bites and Tetanus.

 

Presentation

History

A thorough, detailed history is necessary to facilitate communication between various health-care professionals involved in the treatment of the patient and to document why the plan of care was appropriate. (Photographic documentation should also be considered.) It is extremely important that the chart reflect the following:

  • An adequate initial evaluation

  • An appropriate care plan

  • That the patient was counseled regarding potential complications and importance of early and regular follow-up care

When questioned as to the nature of their injury, patients often mislead the examiner out of embarrassment or fear of legal repercussion. This is particularly common in bites that occur during sexual activity (eg, “love” bites to a breast). Consider all injuries dorsal to the MCP joint to be bite wounds until proven otherwise. Because explanations offered for such wounds often are misleading, extreme caution is necessary. While a careful explanation of the need for an accurate history may elicit the truth from the patient, experienced emergency physicians often treat such injuries as bites regardless of the history.

Most bite wound infections are not present at the initial emergency department (ED) visit. With closed-fist injuries, the initial injury often appears minor to the patient; thus, no care is sought until infection develops.

If a child receives a small laceration to the scalp or forehead during unwitnessed horseplay, carefully ascertain whether a tooth caused the wound, to minimize complications.

Other aspects of a patient's history that may influence care include the following:

  • Tetanus immunization status

  • Time delay from injury to presentation

  • Disability encountered

  • Presence of underlying immunosuppressive disease

Natural history of the wound

Obtain the following information about the natural history of the wound:

  • Circumstances surrounding the injury

  • Precipitating event or activity

  • Exact mechanism of injury

  • Time of occurrence

  • Location of occurrence

  • Whether the other party involved is known to the patient and available should testing be indicated

  • Treatment initiated prior to presentation

Signs and symptoms related to the wound

Obtain the following information about wound-associated signs and symptoms:

  • Pain

  • Fever

  • Swelling

  • Discharge or odor

  • Tobacco, alcohol, or recreational drug use

  • Medications or allergies to medications

  • Tetanus immune status

  • Ability to comprehend the magnitude of injury and to cooperate with the treatment plan

Comorbidities

Comorbid conditions that may place the patient at a higher risk for infection or its sequelae include the following:

  • Diabetes mellitus

  • Chronic edema of the region - Eg, prior ipsilateral axillary node dissection for an upper extremity wound

  • Prior splenectomy

  • Liver disease

  • Immunosuppression

  • Presence of a prosthetic valve or joint

  • Regional arterial or venous disease

Legal considerations

Human bite-injury cases are often assault cases and are more likely to involve the judicial system. With that in mind, documentation should be clear, concise, and complete. Moreover, most jurisdictions require medical professionals to report suspected child abuse.[11]

Physical Examination

A thorough physical examination is necessary to evaluate the overall state of health, comorbidities, nutritional status, and mental status of the patient.

Following the general physical examination, the clinician should turn his/her attention to the wound. Assessment of the wound can be quite difficult and is often inaccurately or inadequately performed.

Adequate examination of the wound may require administration of intravenous (IV) or oral pain medication to ensure patient comfort.

Examine hand injuries through the full range of hand motions, particularly in the case of clenched-fist injuries. Physicians must be wary of any laceration overlying the MCP joint. Additionally, carefully assess bite wounds of the fingers for deeper penetration into the tendon apparatus. Extending the wound may be necessary to fully evaluate underlying structures and the extent of the injury.

Wound characteristics

Important aspects of wound assessment include the following:

  • Location

  • Shape

  • Size

  • Type - Puncture, laceration, avulsion, or crush

  • Depth of penetration

  • Drainage - Quantity, character, odor

  • Presence of a foreign body - Tooth fragments, particulate matter

  • Loss of tissue

  • Tenderness

  • Asymmetry

  • Violation of tendon, cartilage, joint spaces, or bone - This may be difficult to detect on initial examination and may require operative exploration to adequately diagnose

  • Surrounding erythema, edema, cellulitis, or crepitus

  • Neurovascular status

  • Regional lymphadenopathy

The following points should be noted for specific bite wounds:

  • MCP wounds (closed-fist injury) - Integrity of the extensor tendons, signs of infection, crepitus, loss of knuckle height

  • Chomping injuries of the finger - Integrity of the extensor and flexor tendons, evidence of infection (including flexor tenosynovitis)

  • Ear bites - Loss of tissue, violation of cartilage

  • Other bites - Tissue loss, depth of penetration

All bite marks in a young child should raise suspicion of abuse. The normal intercanine distance of an adult is 2.5-4.0 cm. Therefore, any human bite marks with an intercanine distance over 3.0 cm were likely inflicted by an adult.[12]

Documentation guidelines

Although not standard in all centers, the following guidelines for wound documentation in cases of assault have been established by the American Board of Forensic Odontology[13] :

  • Photographic documentation

  • Wound diagram, including notation of arch pattern and intercanine width

  • Bite mark impressions

  • Swabbing of the wound for tissue typing

 

DDx

Diagnostic Considerations

The differential diagnoses of a human bite to the breast are extensive and include inflammatory breast carcinoma, Paget disease, thrombophlebitis, and radiation fibrosis.[14]

Differential Diagnoses

 

Workup

Approach Considerations

Lab studies

No laboratory studies are required unless bacteremia or sepsis is suspected. If indicated, draw appropriate baseline viral titers from the patient and the assailant.[15]

Radiography

Radiography may be useful, particularly in hand injuries or over bone, to reveal fractures, foreign bodies, or air within a joint. If history indicates that a tooth was broken during the incident, a radiograph may be indicated to examine for it. Radiography of chronic wounds may reveal underlying osteomyelitis.

In closed-fist injuries, an underlying metacarpal head fracture is possible. If such a fracture is identified radiographically, the clinician should strongly consider emergent consultation with a hand surgeon in such cases, as there is a high potential for an adverse outcome.

Wound Cultures

Routine culture of all human bite wounds is unnecessary because such testing is costly, demonstrates no growth in more than 80% of cases, and rarely alters first-line therapy. Wounds subsequently manifesting signs of infection, however, often have bacteriologic profiles differing from the initial cultures. Wound cultures are indicated in wounds manifesting signs of infection (eg, cellulitis, swelling, purulence) and in wounds not showing clinical improvement despite seemingly appropriate antimicrobial therapy.

Obtain and grow aerobic and anaerobic cultures for 7-10 days to identify slow-growing pathogens. This allows quantification and identification of bacterial species and their antibiotic susceptibilities. If possible, obtain cultures prior to the initiation of antimicrobial therapy.

 

Treatment

Approach Considerations

Wound cleaning

Meticulous wound care is the cornerstone of human bite wound management. Copious irrigation decreases the incidence of wound infection. Use isotonic sodium chloride solution, dilute povidone-iodine (Betadine), or dilute hydrogen peroxide to thoroughly cleanse the wound. Cleansing is best performed with a 10-mL syringe with an 18-gauge angiocatheter attached. Take care to avoid injection of the tissues and to prevent additional trauma.

Careful debridement of devitalized tissue, particulate matter, and clot is also necessary to reduce the infection risk and to improve the cosmetic result. Faster wound healing and better scarring result from clean, surgically created wound margins.

Wound closure

Wound closure is a source of controversy in the management of patients with human bite wounds. In general, do not close hand wounds, puncture wounds, infected wounds, or wounds more than 12 hours old. Allow such wounds to heal by secondary intention. They may be closed secondarily or revised at a later date.

Head and neck wounds, being in a cosmetically sensitive area, may be closed if they are less than 12 hours old and are not obviously infected. These wounds have been closed with a low incidence of infection, probably because of excellent blood supply and infrequency of edema.

The following points deserve specific mention:

  • Antibiotic prophylaxis is mandatory in these patients.[16]

  • Perform closure in a simple, interrupted fashion, avoiding layered closure with buried sutures.

  • The objective is to provide wound edge approximation that is not watertight and still allow for drainage.

Tetanus prevention

Although rare, human bites have been shown to transmit Clostridium tetani. Assess all patients for tetanus immune status and update as appropriate. According to the recommendations of the US Centers for Disease Control and Prevention (CDC),[17] tetanus immune globulin and the 3-dose vaccine series should be administered to patients with an unknown tetanus vaccine history or those who have received fewer than 3 doses. It is also indicated for patients who received the complete tetanus series, but whose booster administration was more than 5 years ago. For patients with a history of 3 or more doses of tetanus and diphtheria vaccine who received a booster less than 5 years ago, no tetanus booster is required.

These wounds are often several days old and are heavily contaminated or even infected upon first presentation. Bites with no significant skin penetration (abrasions or contusions) require no further care.

Antibiotic use

Antibiotic prophylaxis is warranted if the wound is believed to be at higher risk for infection (eg, significant contamination is present; bone, tendon, or joint space is involved; the bite is on the hand; deep puncture wounds are present; or bites occurring in high-risk patients). The clinician should be aware that the Infectious Diseases Society of America (IDSA) clinical practice guidelines state that all human bite wounds require antibiotic prophylaxis.[18] However, a large clinical trial showed that prophylaxis of human bites that do not penetrate the epidermal layer or are not in high-risk areas is probably unnecessary.[19]

Additional considerations

A fully informed patient may make appropriate choices regarding viral prophylaxis when risks and benefits are clearly explained and understood.

Surgical intervention is frequently necessary. Procedures range from simple wound exploration and debridement to repair of complex structures under magnification.

Human bite wounds at risk for transmission of life-threatening disease require individualization of therapy.

Activity

After initial immobilization of hand injuries in a position of function and elevation, provide instruction regarding resumption of activity. Continue elevation until edema resolves.

In general, early mobilization (ie, 48-72 h postinjury), once improvement is noted, prevents one of the most common and difficult complications of hand injuries, the stiff joint.

Surgical Care

Prehospital care

Recovery of avulsed tissue parts (eg, ear, finger) is an important consideration for prehospital providers. Otherwise, human bite wound management generally is uncomplicated and involves temporary dressing and transport.

Avulsed parts should be wrapped in sterile gauze dressing that is soaked with normal saline and placed in a plastic bag that is, in turn, placed in a container of ice water.

Emergency department care

Closed-fist injuries

An underlying fracture dictates consultation and potentially the need for inpatient treatment under certain circumstances. After appropriate anesthesia, explore the wound for joint space violation or tendon injury. Involvement of the joint space indicates that the patient should be admitted to the hospital. Also consider patients with tendon injuries, which usually are present, for admission.

Proper wound assessment includes using a tourniquet and extending the wound as needed to improve visualization. Provide outpatient treatment of these wounds (careful wound cleansing, antibiotic coverage, bulky dressing or splint, elevation) only in consultation with hand or orthopedic service. Early, mandatory follow-up care is essential.[20]

Treat noninfected wounds that appear to violate the tendon apparatus in the same manner as noninfected closed-fist injuries.

Puncture wounds

These most commonly are encountered about the head. Such wounds are difficult to clean adequately unless extended to allow for effective irrigation. Even in the absence of infection, such wounds are best left open and closed secondarily, if cosmetically necessary.

Bites to the ear or nose

When associated with tissue loss, these wounds require consultation with plastic surgery or ear, nose, and throat (ENT) service. Seeking consult for a bite that violates cartilage in these areas also is prudent because of poor blood supply to cartilage and difficulties in treating chondritis.[21]

Antibiotic Prophylaxis

The literature regarding prophylaxis of human bite wounds is sparse. Only 2 randomized, controlled trials directly address the question. The first study indicated that prophylactic antibiotics are very effective in preventing infection. Patients with acute, noninfected human bites to the hand were randomized to prophylaxis with placebo, an oral cephalosporin, or a parenteral cephalosporin plus penicillin. Bites involving joints or tendons were excluded from the study. The results were dramatic, with infection developing in 47% of the placebo group but in none of the patients treated with antibiotics.[22]

In a larger, subsequent trial involving patients with “low-risk” human bites, no statistically significant difference was found in the placebo group compared with the group treated with antibiotics. In the study, patients were randomized to placebo or an oral cephalosporin plus penicillin. This trial excluded patients with bites to the hands, feet, or cartilaginous structures, and no patient in this trial had a bite wound that penetrated deep to the epidermis.[19]

A large, retrospective series examining human bite wounds in children found that none of the bites manifesting as abrasions became infected, while the rate of infection was much higher in bite wounds that caused punctures or lacerations.[23]

One can draw the following conclusions from these data:

  • Acute human bites that do not penetrate the epidermal layer probably do not need antibiotic prophylaxis as long as they do not involve the hands, feet, or joints or cartilaginous structures

  • Human bites that completely penetrate the epidermal layer, as well as bites that involve joints or cartilaginous structures, probably merit antibiotic prophylaxis, but the evidence is not strong.

  • Human bites to the hand are at high risk for infection and should be given antibiotic prophylaxis

Treatment of Infected Human Bite Wounds

The current recommendations from the IDSA call for the use of amoxicillin/clavulanate or ampicillin/sulbactam in patients with an infected human bite wound. Cephalexin, which is commonly used for skin and soft-tissue infections, is ineffective against E corrodens, an important pathogen in infected human bites. Trimethoprim-sulfamethoxazole (TMP-SMZ) or a quinolone such as levofloxacin or moxifloxacin in addition to clindamycin is an acceptable alternative in the penicillin-allergic patient.[18]

Infected closed-fist injuries are a special case because of the deep nature of these infections and the relatively poor vascular supply to the tendons and other connective tissue. Admitting patients for IV antibiotic therapy is generally considered appropriate is these cases. Surgical debridement and drainage also may be necessary

Hepatitis B

Offer the patient a single dose of hepatitis B immunoglobulin (HBIG), as well as an accelerated course of hepatitis B vaccine with doses at 0, 1, and 2 months (unless the patient is known to be immune).

If the assailant's hepatitis B status is unknown but is considered high risk and the assailant is unavailable for testing, again offer an accelerated course of the hepatitis B vaccine to the patient.

If the assailant's status is unknown but is considered low risk and the assailant is unavailable for testing, the accelerated course of the hepatitis B vaccine may be offered to the patient with the understanding that the likelihood of disease transmission is low.

Human immunodeficiency virus

HIV transmission has been noted only rarely after a human bite. Exposure to saliva alone is not considered a risk factor for HIV (or hepatitis) transmission. Transmission requires HIV-infected blood mixed in the saliva of the biter and a skin break on the victim. The reverse consideration also is important in that blood drawn from an HIV-infected victim would come in contact with the mucous membranes of the biter. A 2005 recommendation from the Centers for Disease Control and Prevention (CDC) states that postexposure prophylaxis with a 28-day course of highly active antiretroviral therapy (HAART) should be used in either of these 2 scenarios.[24]

Draw a baseline specimen from the patient to determine preexposure HIV status, and retest him or her at 3 and 6 months. Failure to convert to HIV-positive status at 6 months makes transmission highly unlikely.

Surgical Indications

Surgical intervention is frequently necessary and ranges from simple wound exploration and debridement to repair of complex structures under magnification.

Certain patients (eg, children, persons who are emotionally unstable, persons who are mentally handicapped) may require surgical exploration under anesthesia to adequately examine the wound.

Indications for surgical intervention include the following:

  • Severe soft-tissue infection

  • Abscess

  • Joint penetration

  • Underlying fracture

  • Tendon laceration

  • Osteomyelitis

  • Tenosynovitis

  • Septic arthritis

  • Neurovascular compromise or injury to a complex structure (eg, facial nerve, parotid duct)

  • Foreign body

Surgery for Head and Neck Wounds

The goals of treating human bites to the head and neck region are the restoration of the patient's facial appearance and function.[25, 26] In the past, these wounds were routinely left open because of the high rate of wound infection; however, care of these patients has undergone marked changes with the introduction of broad-spectrum antibiotics and the evolution of microsurgical techniques. The development of broad-spectrum antibiotics gradually led to general acceptance of the idea that patients who present early and without obvious infection are candidates for primary wound closure.[27]

Once surgeons became familiar with and accepted this approach because of its good clinical results, aggressive reconstructive techniques evolved in the acute setting. These techniques have proven to be safe and effective, yielding an acceptably low rate of morbidity, and they do not leave the patient with a potentially significant facial deformity while awaiting reconstruction. More importantly, the ultimate results of primary reconstruction are clearly superior to those of delayed reconstruction.

Many options are available to the surgeon, including primary closure, skin grafting, composite grafting, the use of local flaps, and microsurgical replantation.

Lip wounds

Lip wounds are among the most common facial bite wounds. Vermillion defects may be reconstructed with mucosal advancement flaps. Wounds measuring up to a third of the length of the lip may be closed by using a wedge or chevron excision and approximating the 2 cut edges.[28] Perform muscular reapproximation of the orbicularis oris with interrupted, buried, absorbable sutures to assure continuity of the sphincteric muscular ring.

Small (< 1.5 cm2) lip segments have been successfully replanted as composite grafts when a segment of lip has been amputated and is available for reattachment. However, the survival of such grafts is often questionable. Patients with small tissue loss may benefit more from primary wound closure or from the use of one of the available local flaps.

Larger defects may require a local flap (eg, Bernard advancement flap, Gillies fan flap, Karapandzic myocutaneous flap) or a lip switch procedure (eg, with an Abbé or Estlander flap).[29]

Large amputated lip segments have been successfully replanted using microvascular techniques, with the results being unmatched by any other reconstructive technique.[30] No other donor tissue matches replanted lip with regard to symmetry, contour, shape, color, texture, or motion. Return of muscle function and protective sensation is fairly predictable.

Although this approach is reliable, however, it is not universally applicable. The surgeon must have adequate experience in microvascular techniques, and the treating facility must have microsurgical equipment. Caution patients against smoking in the postoperative period to avoid the vasoconstrictive effects of nicotine.

Vascular repair

An artery may be anastomosed to the remaining labial artery if it is identifiable in the severed lip.

Veins are small and often unidentifiable. Veins may be repaired primarily or by using a vein graft. When no vein is found and when 2 arteries are located in the severed segment, 1 of the arteries may be anastomosed to a facial vein; this creates an arteriovenous fistula that aids venous drainage of the amputated part through retrograde flow.

Venous congestion is the most likely cause of failure in lip replantation. In general, when no venous anastomosis is performed, patients require venous decompression for 4-6 days until the wound is adequately revascularized from surrounding tissue.

Venous drainage

Venous drainage may be achieved in several ways. All methods involve notable bleeding and frequently require administration of blood transfusions, which increase the risk of disease transmission. Some recommend systemic anticoagulation with heparin, while others advocate local injection of heparin into reattached tissue. Bleeding occurs from the suture line, which should be kept free of clot or crusting to allow the egress of venous blood.

Leeches actively remove blood and may be applied to the suture line. Passive oozing from the leech bite continues to provide artificial venous outflow after they are removed. An anticoagulant (hirudin) in leech saliva that is injected when it bites enhances venous egress.

Give patients undergoing leech therapy appropriate antibiotic prophylaxis against infection by Aeromonas hydrophila, which is found in the gastrointestinal (GI) tract of the leech.

Ear wounds

Ear wounds are also common facial bites, because of the prominent position of the ears on the head. Coverage of exposed cartilage and restoration of shape are the primary concerns. Similar to lip bites, small bites on the ears can be closed primarily and may require wedge excision.

Alternatives for covering exposed cartilage in the presence of skin deficits are the use of postauricular flaps or temporoparietal fascial flaps covered with thick split-thickness skin grafts. Helical advancement may be performed to reconstruct helical defects.

Small amputated parts may be replaced by composite grafts. If the composite graft fails, débride the wound, close the skin over the cartilage, and delay definitive reconstruction until infection or inflammation subsides.[31]

Salvaged denuded cartilage can be preserved by placing it in an abdominal or cervical pocket or under postauricular skin.

Larger amputated segments may be replanted by using microvascular techniques similar to those described for the lip. However, these procedures tend to fail because of the small caliber of the vessels. Reanastomosing the veins may be difficult or impossible; alternative techniques for ensuring venous drainage may be needed.

In the absence of microvascular capabilities, amputated cartilage may be skeletonized and placed in a subcutaneous pocket for use during later reconstruction.

Delayed reconstruction may be performed by using a retroauricular flap, helical advancement, or cartilage or composite grafting, depending on the residual defect.

Cheek wounds

Cheek wounds are frequently amenable to primary closure. Injuries with great tissue loss may be closed with cervicofacial, nasolabial, or other locoregional flaps.

Eyelid wounds

Bites to the eyelid are infrequent but pose a particular threat in terms of eye closure and corneal protection. A full-thickness graft from the contralateral lid may be used when only a skin deficit is encountered. A composite graft from the contralateral lid may be used for defects of the tarsal plate.

Nose wounds

Nose wounds and resultant nose reconstruction can be challenging; reconstructive considerations include the following:

  • Cartilaginous defects may require grafts from the septum, ear, or costal cartilages; a composite cartilage graft harvested from the ear may also be necessary

  • For small defects of the nasal dorsum, soft-tissue coverage may require a dorsal nasal flap

  • A nasolabial flap (either pedicle or island), forehead flap, or Washio flap may be required for larger defects

Indications for hospitalization

Acutely, any patient with an injury severe enough to require operative exploration should be observed overnight postoperatively. Some may well require a longer stay, but this is dictated by the specific clinical situation. In certain high-risk situations, admission may also be reasonable (eg, noncompliant alcoholic patient with a bite wound to the hand).

Outpatient Care and Monitoring

Patients evaluated early, without evidence of infection, and without hand wounds may be treated on an outpatient basis without antibiotics. However, it is generally recommended that patients return within 48-72 hours for reassessment. The development of any signs or symptoms of infection indicate a need for the patient to seek immediate medical attention.

Subacutely, patients with mild-to-moderate infections or hand wounds without infection may also be treated on an outpatient basis, with oral antibiotics, if they are likely to be compliant with the overall treatment plan. Some indications for admission include the following:

  • Evidence of systemic toxicity (fever, elevated WBC count, ill appearance)

  • Infected bite wounds of the hand

  • Failure of previously instituted outpatient treatment

Consultations

A multidisciplinary approach can lead to maximum patient benefit in certain circumstances. Refer to a hand surgeon any hand injury with suspicion of tendon injury, fracture, joint-space violation, retained foreign body, injury to a nerve or vessel, or significant tissue loss. These have a significant risk for permanent disability and should be referred to a hand therapist.

Refer to a plastic surgeon, otolaryngological (ENT) surgeon, or maxillofacial surgeon any head or neck wound with suspicion of violation of cartilage, retained foreign body, or injury to nerves, vessels, or another complex structure. Also refer to the appropriate surgical subspecialist any wounds involving significant tissue loss that has created difficult closure.

 

Guidelines

Guidelines Summary

The IDSA recommends amoxicillin-clavulanate as empiric therapy for treatment of human bite wounds. Ampicillin-sulbactam is an alternative that can be administered intravenously. In patients who are unable to tolerate beta-lactam antibiotics, moxifloxacin is recommended. If moxifloxacin is unavailable, another quinolone such a ciprofloxacin or levofloxacin can be combined with metronidazole.[15]

 

Medication

Medication Summary

Empiric antibiotic therapy needs to be aimed at E corrodens, a wide variety of beta-lactamase–producing anaerobes, and S aureus.

There are no set guidelines to cover empirically for MRSA. However, if an abscess or gross purulence is present, treatment for MRSA should be initiated pending final culture results. Eikenella corrodens may not be covered by first-generation cephalosporins. These isolates are also resistant to clindamycin, penicillinase-resistant semisynthetic penicillins, macrolides, and aminoglycosides.

In an in vitro study of 50 infected human bites, Talan et al found that amoxicillin-clavulanic acid and moxifloxacin demonstrated excellent activity against the most common isolates.[32] The combination of a penicillinase-resistant penicillin with a second- or third-generation cephalosporin and metronidazole would provide an alternative.

Strong consideration should be given to admitting patients with human bite infections, especially those with bites to the hands or cartilage.[7]

Antibiotics, Other

Class Summary

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.

Amoxicillin and clavulanic acid (Augmentin, Augmentin XR, Amoclan)

This drug combination treats bacteria that are resistant to beta-lactam antibiotics. It is the most effective and economical choice for outpatient therapy, unless contraindicated. In children over age 3 months, base the dosing protocol on amoxicillin content.

Because of different amoxicillin/clavulanic acid ratios in the 250-mg tablet (250/125) versus the 250-mg chewable tablet (250/62.5), do not use the 250-mg tablet until the child weighs more than 40 kg.

Doxycycline (Doryx, Vibramycin, Adoxa)

Doxycycline is an alternative for oral therapy in the penicillin-allergic patient. It inhibits protein synthesis and, therefore, bacterial growth by binding to 30S and possibly 50S ribosomal subunits of susceptible bacteria.

Doxycycline is a broad-spectrum, synthetically derived bacteriostatic tetracycline antibiotic. It is almost completely absorbed, concentrates in bile, and is excreted in urine and feces as a biologically active metabolite in high concentrations.

Cefoxitin sodium (Mefoxin)

This is an alternative drug for infected bites Cefoxitin is a second-generation cephalosporin indicated for gram-positive cocci and gram-negative rod infections. Infections caused by cephalosporin- or penicillin-resistant, gram-negative bacteria may respond to cefoxitin.

Cefoxitin inhibits bacterial cell-wall synthesis by binding to 1 or more penicillin-binding proteins. It inhibits the final transpeptidation step of peptidoglycan synthesis, resulting in cell-wall death.

Ampicillin sodium and sulbactam (Unasyn)

This drug combination, of a beta-lactamase inhibitor and ampicillin, covers skin, enteric flora, and anaerobes. It is not ideal for nosocomial pathogens.

The medication interferes with bacterial cell-wall synthesis during active replication, resulting in bactericidal activity against susceptible organisms. It can be administered as an alternative to amoxicillin in patients who are unable to take oral medication.

Ticarcillin disodium and clavulanic acid (Timentin)

This drug combination inhibits biosynthesis of cell wall mucopeptide and is effective during the stage of active growth.

Moxifloxacin (Avelox)

Moxifloxacin inhibits the A subunits of deoxyribonucleic acid (DNA) gyrase, resulting in inhibition of bacterial DNA replication and transcription.

Immunizing Agents

Class Summary

These agents are used to passively immunize patients against tetanus.

Tetanus immunoglobulin (HyperTET S/D)

This is used for passive immunization of any person with a wound that may be contaminated with tetanus spores.

 

Questions & Answers

Overview

Are human bites dangerous?

How are human bites characterized?

What is the pathophysiology of clenched-fist human bite injuries?

What is the pathophysiology of occlusive human bite injuries?

What is the pathophysiology of disease transmission in human bite wounds?

How do human bite wounds occur?

What is the incidence of human bite wounds in the US?

What is the incidence of human bite wounds in the UK?

What are the demographics of human bite wounds?

What is the prognosis of human bite wounds?

What complications are associated with human bite wounds?

When should a patient with a human bite wound seek additional care?

What information should be provided to patients with human bite wounds?

Presentation

What information should be included in the chart of patients with human bite wounds?

Why is the clinical history of human bite wounds difficult to determine?

What other aspects of a patient history are relevant in the care of human bite wounds?

What information about how the injury occurred should be obtained from a patient with a human bite wound?

What information should be obtained about signs and symptoms in patients with human bites?

Which comorbid conditions place patients with a human bite wounds at a higher risk for infection?

What are the legal considerations in the treatment of human bite wounds?

How is a physical exam for human bite wounds performed?

How is a human bite wound evaluated?

What bite-specific information should be noted in the assessment of human bite wounds?

What are the guidelines for documentation in cases of human bite wounds?

DDX

What are the diagnostic considerations in human bite wounds?

What are the differential diagnoses for Human Bites?

Workup

Which lab studies are indicated in the workup of human bite wounds?

Which imaging studies are indicated in the workup of human bite wounds?

What are the indications for wound cultures in the workup of human bites?

Treatment

How is a human bite wound cleaned?

What is involved in closing human bite wounds?

What is involved in preventing tetanus in human bite wounds?

What is the role of antibiotics in the treatment of human bite wounds?

What are additional considerations in the treatment of human bite wounds?

What activity restrictions are indicated in the treatment of human bite wounds?

What prehospital care is indicated in the treatment of human bite wounds?

What emergency care is indicated in the treatment of closed-fist human bite injuries?

What emergency care is indicated in the treatment of puncture wounds from human bites?

What emergency care is indicated in the treatment of human bites to the ear or nose?

What is the role of antibiotic prophylaxis in the treatment of human bite wounds?

When is prophylaxis antibiotic therapy indicated in the treatment of human bite wounds?

What treatment is indicated for infected human bite wounds?

When is hepatitis B vaccine indicated in patients with human bite wounds?

When is HIV postexposure prophylaxis indicated in patients with human bite wounds?

What is the role of surgical intervention in the treatment of human bite wounds?

What are the surgical indications for human bite wounds?

What treatment is indicated in head and neck wounds from human bites?

What treatment is indicated for lip wounds caused by human bites?

What is the role of vascular repair in the treatment of lip wounds from human bites?

What is the role of venous drainage in the treatment of lip wounds from human bites?

How are ear wounds caused by human bites treated?

How are cheek wounds caused by human bites treated?

How are eyelid wounds caused by human bites treated?

How are nose wounds caused by human bites treated?

When is inpatient care indicated for human bite wounds?

What follow-up care and monitoring is indicated in patients with human bite wounds?

Which specialist consultations are indicated in the treatment of human bite wounds?

Guidelines

What are the treatment guidelines for human bite wounds?

Medications

Which medications are indicated in the treatment of human bite wounds?

Which medications in the drug class Immunizing Agents are used in the treatment of Human Bites?

Which medications in the drug class Antibiotics, Other are used in the treatment of Human Bites?