Fight bite (human bite over MCP)MANAGEMENT

FOREARM, WRIST & HAND · 12 SECTIONS

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453 items

☷ Legend

01Approach to the Critical Patient/attcp42

Immediate threats and escalation

›Initial priorities

›Sepsis physiology

›Hypotension or altered mentation triggers resuscitation bay

›Lactate when systemic toxicity

›Limb threat

›Rapidly worsening pain

›Pain with passive finger extension

›New motor deficit

›New sensory deficit

›High risk anatomy

›Dorsal MCP bite mark

›Suspected extensor tendon violation

›Suspected MCP joint violation

›Early specialist involvement

›Hand surgery or orthopedics

›Any suspicion of joint penetration

›Any suspicion of tendon penetration

›Purulence

›Significant swelling with limited ROM

›Infectious diseases

›Immunocompromised host

›Recurrent infection or failure of first-line therapy

›Immediate management targets

›Time-to-antibiotics

›Within 1 hour when sepsis physiology

›As soon as possible when fight bite suspected

›Source control

›If septic arthritis suspected, urgent operative washout pathway

›If abscess present, drainage pathway

Neurovascular and functional baseline

›Documentation set

›Vascular status

›Capillary refill

›Radial pulse

›Ulnar pulse

›Sensory status

›Median nerve distribution

›Ulnar nerve distribution

›Radial nerve distribution

›Motor status

›Finger extension strength

›Finger flexion strength

›Intrinsic hand function

02History/hx42

Exposure and timeline

›Bite context

›Mechanism pattern

›Closed-fist strike to teeth

›Direct human bite

›Time since injury

›Less than 12 hours

›12 to 24 hours

›More than 24 hours

›Wound progression

›Increasing pain

›Increasing swelling

›Purulent drainage

›Hand function at time of injury

›Position of hand during impact

›MCP flexed at impact

›MCP extended after impact

›Immediate functional change

›Loss of extension

›Loss of flexion

›Grip weakness

Host risk and infectious risk

›Comorbid risk

›Diabetes mellitus

›Poor glycemic control

›Neuropathy

›Immunocompromise

›Chronic steroids

›Biologic therapy

›HIV

›Medication risk

›Anticoagulants

›DOAC

›Warfarin

›Antibiotic exposure

›Recent beta-lactam

›Recent MRSA-active agent

›Immunization and bloodborne risk

›Tetanus status

›Unknown or incomplete series

›Last booster more than 5 years

›Blood exposure

›Assailant oral bleeding reported

›Patient open wound blood exposure

03Physical Exam/exam47

Wound and local infection findings

›Wound assessment

›Location pattern

›Dorsal MCP over 3rd MCP

›Dorsal MCP over 4th MCP

›Dorsal MCP over 5th MCP

›Appearance

›Puncture wound

›Laceration

›Devitalized edges

›Drainage

›Serous

›Purulent

›Infection severity

›Cellulitis extent

›Erythema margin

›Lymphangitic streaking

›Deep space concern

›Fluctuance

›Pain out of proportion

Tendon, joint, and compartment focused exam

›MCP joint involvement clues

›Range of motion limits

›Pain with MCP flexion

›Pain with MCP extension

›Joint effusion

›MCP swelling focal

›Pain with axial loading

›Extensor tendon involvement clues

›Extension function

›Inability to extend digit against resistance

›Extension lag at MCP

›Wound behavior with motion

›Gaping or drainage with finger flexion

›Visible tendon

›Compartment syndrome screening

›Disproportionate pain

›Worsening despite analgesia

›Pain with passive stretch

›Late findings

›Paresthesia

›Weakness

PITFALLS

›Common misses

›Small dorsal puncture with deep joint seeding

›MCP joint violated when fist was flexed

›Skin wound appears minor when hand is extended

›Primary closure increases infection risk

›Closure traps inoculum

›Closure obscures evolving deep infection

04Differential Diagnosis/ddx27

Primary and limb-threatening diagnoses

›Infection syndromes

›Septic arthritis of MCP joint

›ICD-10 M00.9

›SNOMED CT septic arthritis

›Flexor tenosynovitis

›ICD-10 M65.9

›Kanavel pattern consideration

›Deep space hand infection

›Thenar space infection

›Midpalmar space infection

›Structural injury syndromes

›Extensor tendon laceration

›ICD-10 S66.3

›SNOMED CT extensor tendon injury

›Metacarpal fracture

›ICD-10 S62.3

›SNOMED CT metacarpal fracture

Mimics and co-injuries

›Noninfectious considerations

›Inflammatory arthritis flare

›Gout

›Rheumatoid arthritis

›Hematoma with anticoagulation

›Expanding swelling without erythema early

›Co-pathogens and complications

›Osteomyelitis risk

›ICD-10 M86.9

›Delayed presentation more than 48 to 72 hours

05Laboratory Tests/lt24

Infection severity and operative readiness

›Baseline labs when systemic signs or deep infection concern

›CBC

›Leukocytosis supports severe infection

›Normal WBC does not exclude septic arthritis

›CRP

›Trend marker for response

›Elevated supports deep infection

›ESR

›Adjunct marker

›Slow to normalize

›Sepsis labs when unstable

›Lactate

›Elevated supports hypoperfusion

›Serial lactate for resuscitation response

›Blood cultures

›Before antibiotics when feasible in sepsis physiology

›Lower yield without systemic features

Microbiology from the site

›Culture strategy

›Superficial swab limitation

›Poor correlation with deep pathogens

›Contamination common

›Deep specimen preference

›Aspirate from joint when safe and trained

›Operative culture as gold standard

06Diagnostic Tests/dt41

Scoring Systems

›Deep infection screening patterns

›Kanavel signs for flexor tenosynovitis

›Fusiform swelling

›Digit held in flexion

›Pain with passive extension

›Flexor sheath tenderness

›Septic arthritis likelihood pattern

›Severe pain with ROM

›Effusion

›Fever may be absent early

Radiographs

›Plain films

›Views

›Hand 3-view

›Targeted digit views when needed

›Findings

›Tooth fragment foreign body

›Metacarpal head fracture

›Subcutaneous gas

›Limitations

›Early osteomyelitis often normal

›Radiolucent foreign bodies not excluded

MRI

›Soft tissue and bone complication evaluation

›Osteomyelitis concern

›Persistent pain and swelling beyond expected

›Failure of appropriate antibiotics

›Tendon sheath involvement

›Flexor tenosynovitis extent

›Deep space infection mapping

›Constraints

›Time and access limitations in acute ED setting

›Metal hardware artifact considerations

›Alternative imaging when MRI not feasible

›Foreign body detection

›Tooth fragment localization

›Occult fracture detail

›Gas and abscess mapping

›Deep gas collections

›Abscess extension

›Constraints

›Lower sensitivity than MRI for early osteomyelitis

›Radiation exposure

07Disposition/dispo30

Admission and operative pathways

›Admit criteria

›Suspected joint or tendon violation

›Operative washout planned

›Serial exams needed

›Systemic infection features

›Fever with toxicity

›Hypotension or tachycardia out of proportion

›High-risk host

›Immunocompromised

›Poor diabetes control

›Transfer criteria

›No local hand surgery capability

›Suspected septic MCP joint

›Suspected tendon laceration

›Rapid progression

›Worsening pain and swelling over hours

›Rising lactate or shock

Discharge criteria and follow-up

›Discharge only when low risk

›Superficial wound without deep structure concern

›Full painless ROM

›No focal joint tenderness

›Reliable follow-up within 24 to 48 hours

›Recheck for evolving infection

›Reassessment of function

›Follow-up timing

›Hand surgery or plastics

›24 hours when any doubt

›48 to 72 hours for clearly superficial wounds improving

›Return visit triggers planned

›Mandatory next-day reassessment when fight bite suspected

08Treatment/t103

Immediate life-saving interventions

›Stabilization when systemic toxicity

›IV access and fluids

›Balanced crystalloid bolus for hypotension

›Reassessment after each bolus

›Early broad-spectrum IV antibiotics

›Ampicillin-sulbactam preferred when severe

›Vancomycin added when MRSA risk and severe infection

›Source control urgency

›If septic arthritis suspected, operative washout pathway

›NPO status

›Analgesia without masking neurovascular checks

Wound care and irrigation

›Local management principles

›Copious irrigation

›High-volume saline

›Avoid high-pressure injection into tissue planes

›Exploration thresholds

›High suspicion wounds require specialist exploration

›ED exploration limited by depth and function

›Closure strategy

›Leave open in most fight bites

›Delayed closure after infection control

›Tetanus prophylaxis

›Booster criteria

›Dirty wound and last booster more than 5 years

›Unknown status treated as not up to date

›Tetanus immune globulin criteria

›Unknown or incomplete series with dirty wound

Antibiotics and dosing

›Empiric pathogen coverage

›Typical flora

›Streptococci

›Staphylococcus aureus

›Eikenella corrodens

›Oral anaerobes

›Agents to avoid

›Cephalexin monotherapy lacks Eikenella coverage

›Clindamycin monotherapy lacks Eikenella coverage

›Oral regimen for low-risk outpatient

›Amoxicillin-clavulanate

›Adult dose

›875 mg amoxicillin with 125 mg clavulanate PO q12h

›Duration 3 to 5 days prophylaxis when early and uninfected

›Duration 5 to 7 days when mild cellulitis

›IV regimen for deep infection concern or admission

›Ampicillin-sulbactam

›Adult dose

›3 g IV q6h

›Transition to oral when improving and source control achieved

›Total duration guided by depth

›Penicillin allergy pathways

›Non-anaphylactic history

›Cephalosporin plus anaerobe coverage

›Cefuroxime

›500 mg PO q12h

›Add metronidazole

›500 mg PO q12h

›Anaphylaxis history

›Doxycycline plus metronidazole

›Doxycycline

›100 mg PO q12h

›Avoid in pregnancy and young children

›Metronidazole

›500 mg PO q12h

›Moxifloxacin monotherapy option

›400 mg PO daily

›Avoid in pregnancy and pediatrics

›MRSA coverage when indicated

›Indications

›Purulent infection

›Prior MRSA colonization or infection

›Failed beta-lactam therapy

›Add-on agents

›TMP-SMX

›1 to 2 DS tabs PO q12h

›Pair with amoxicillin-clavulanate for streptococcal coverage

›Doxycycline

›100 mg PO q12h

›Pair with amoxicillin-clavulanate for streptococcal coverage

Operative and procedural pathways

›Joint penetration or septic arthritis concern

›Hand surgery washout pathway

›Operative irrigation and debridement

›Deep cultures intra-op

›Abscess pathway

›Incision and drainage when superficial and safe

›Avoid tendon and joint spaces without specialist support

›Packing selective and minimal

›Analgesia strategy

›Non-opioid base

›Acetaminophen

›1000 mg PO q6h

›Maximum 4000 mg per day

›Ibuprofen

›400 to 600 mg PO q6h

›Avoid in CKD and high GI risk

›Opioid rescue when severe pain

›Hydromorphone

›0.2 to 0.5 mg IV q10 min PRN

›Stop escalation if sedation or hypoventilation

›Regional anesthesia consideration

›Digital block

›Lidocaine 1% without epinephrine

›3 to 5 mL total per digit

›Aspirate before injection

›Avoid injecting into infected closed spaces

09Special Populations/sp30

Pregnancy

›Antibiotic selection

›Preferred agents

›Amoxicillin-clavulanate acceptable

›Ampicillin-sulbactam acceptable

›Avoidance

›Doxycycline avoidance

›Fluoroquinolone avoidance

›Imaging considerations

›Radiographs with shielding acceptable when indicated

›MRI preferred for osteomyelitis concern when needed

Geriatric

›Higher complication risk

›Delayed presentation common

›Higher admission threshold

›Medication safety

›Renal dosing attention

›Amoxicillin-clavulanate adjustment in CKD

›Ampicillin-sulbactam adjustment in CKD

›Opioid delirium risk

›Lower starting doses

›Frequent reassessment

Pediatrics

›Unique considerations

›Nonaccidental injury context when history inconsistent

›Smaller tissue planes and rapid progression

›Weight-based antibiotic dosing

›Amoxicillin-clavulanate

›25 to 45 mg per kg per day amoxicillin component divided q12h

›Maximum adult dose cap

›Ampicillin-sulbactam

›50 mg per kg per dose ampicillin component IV q6h

›Maximum adult dose cap

10Background/b30

Epidemiology

›Frequency and risk

›Human bites high infection risk compared with many animal bites

›Hand and MCP region highest-risk location

›Delayed presentation increases risk markedly

›Fight bite clinical pattern

›Small dorsal wound with deep inoculation to MCP joint

Pathophysiology

›Mechanism

›Tooth penetration through extensor mechanism

›MCP flexion at impact seeds joint capsule

›MCP extension after impact closes skin wound and traps bacteria

›Common pathogens

›Eikenella corrodens resistant to clindamycin and first-generation cephalosporins

›Polymicrobial mixture with anaerobes common

›Complication pathways

›Septic arthritis progression

›Rapid cartilage destruction

›Long-term stiffness and disability

›Osteomyelitis progression

›Higher risk with delayed source control

›Prolonged antibiotics and possible surgery

Therapeutic Considerations

›Core principles

›Early antibiotics plus source control when deep involvement

›Leave wounds open when high contamination and hand location

›Splinting for comfort and function preservation

›Evidence framing

›Early prophylactic antibiotics reduce infection risk in high-risk hand bites

›Operative washout required when joint or tendon involvement suspected

›Consensus recommendation

›Class I for urgent hand surgery consult when fight bite suspected

›Class I for amoxicillin-clavulanate or ampicillin-sulbactam as first-line empiric coverage

11Patient Discharge Instructions/pdi23

Copy discharge instructions

›Discharge bundle

›Wound care

›Keep wound clean and dry

›No occlusive closure or ointment packing unless instructed

›Elevation and swelling control

›Hand elevated above heart as much as possible for 48 hours

›Ice 10 to 15 minutes at a time with a barrier

›Medications

›Take antibiotics exactly as prescribed

›Pain control with acetaminophen and ibuprofen if safe

›Activity limits

›Avoid punching or contact sports until cleared

›Limit gripping if painful

›Return to ED now for

›Fever

›Worsening redness or swelling

›Increasing pain

›Pus drainage

›New numbness or weakness

›Inability to fully move the finger

›Follow-up

›Recheck within 24 to 48 hours even if improving

›Hand surgery follow-up when arranged

12References/r14

Evidence-based sources and guidance

›Clinical guidance set

›IDSA skin and soft tissue infection guidance covering bite wounds

›Empiric polymicrobial coverage including anaerobes

›Amoxicillin-clavulanate first-line outpatient option

›Hand infection and fight bite reviews in emergency medicine and hand surgery literature

›High complication risk with delayed presentation

›Operative management when joint or tendon involvement suspected

›Evidence level mapping for this tool

›ACEP Level C style consensus

›Early antibiotics for high-risk human bites to the hand

›Avoid primary closure for contaminated hand bites

›Class I consensus

›Urgent hand surgery consult when fight bite suspected

›Ampicillin-sulbactam IV when severe or deep infection suspected

Evidence & Review

Reviewed by SymptomDx Medical Team · Last reviewed March 6, 2026

SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.