Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Bite to the Hand

Basics
Description
  • Hand bites (direct or indirect) are serious injuries that, if not managed correctly, may result in substantial morbidity to the hand.
  • A direct bite to the hand, such as a dog bite or intentional human bite, can occur in any location.
  • The more common clenched-fist (or indirect) injury occurs over the MCP joint (the knuckle) when a fist strikes an opponent’s mouth.
    • This seemingly benign injury is, in fact, treacherous and, unfortunately, common.
    • A tooth may lacerate the extensor tendon, the joint capsule, or the joint itself.
    • As the digit is straightened, the underlying wound is obscured by normal soft tissue.
  • Classification:
    • Minor: Small puncture wound
    • Major: Large lacerations and soft-tissue damage (2-5 cm, exposed bone or cartilage, tendon rupture)
  • Synonyms: Clenched fist injury; Fight bite; Dog or cat bite
General Prevention
  • Little can be done in terms of prevention for direct or indirect bites except to counsel patients about avoiding unknown animals and fighting, respectively.
  • Complications may be minimized by recognizing the human bite wound as a serious injury and treating with early irrigation, debridement, and appropriate antibiotics.
Epidemiology
Incidence
  • Common
  • >1 million dog bites reported annually
Risk Factors
  • Alcohol abuse
  • Fighting
Etiology
  • Fist fights
  • Dog or cat exposure
Associated Conditions
Fractures
 
Diagnosis
Signs and Symptoms
  • Signs:
    • Puncture or laceration to the hand is present.
    • Associated swelling and erythema may be present.
    • Cellulitis and lymphangitis are present if an infection occurs.
    • If a tendon has been lacerated, the patient may experience difficulty with finger extension.
  • Symptoms:
    • Decreased hand function, such as difficulty with grasping or moving an individual digit
    • Pain
History
Many combatants are embarrassed or hesitant to admit injury to this region or the mechanism of injury and consequently present late for evaluation and treatment.
 
Physical Exam
  • Examine the hand closely for any sign of skin puncture, particularly over the 3rd and 4th MCP joints in instances of clenched-fist injuries.
  • Assess the motor, sensory, and vascular status of the hand and digits.
  • If the injury is of a clenched-fist type, have the patient make a fist, if possible; this procedure may reveal the underlying soft-tissue damage and may facilitate deep wound inspection.
  • In clenched-fist injuries, the damage to underlying structures is proximal to the skin wound when the fingers are in the extended, anatomic position.
Tests
Lab
Cultures in the acute period before surgical debridement are unlikely to be helpful.
 
Imaging
  • Obtain radiographs of the hand to assess for fracture and tooth fragments.
  • In subacute presentations, look for osteomyelitis.
Differential Diagnosis
Any puncture wound over the MCP joints must be regarded with great suspicion and treated as a clenched-fist-type bite injury.
 
Treatment
General Measures
  • If the patient has not been immunized within the past 10 years, tetanus toxoid should be administered.
  • The most important therapeutic interventions are aggressive irrigation and debridement, to remove all devitalized tissue and to irrigate the wound copiously with normal saline solution, povidone-iodine (Betadine), or both.
  • The wound may need to be extended surgically to facilitate exposure of the injured tissue.
  • In clenched-fist injuries, the skin wound is distal to the zone of deeper injury.
  • After irrigation and debridement, the wound should be packed, and the hand should be immobilized and elevated.
  • Do not suture bite wounds.
  • Antibiotics should be commenced (amoxicillin [Augmentin] is a reasonable 1st line agent) and should be continued for 5-7 days in the absence of overt infection.
  • At 24 hours, the packing should be removed, the patient should be reexamined, and warm soaks should be started.
  • If infection is present, the wound should undergo repeat irrigation and debridement, and the patient should be admitted for parenteral antibiotic therapy.
  • For patients presenting late to evaluation and treatment, and for those in whom infection is manifest, urgent irrigation and debridement followed by parenteral antibiotics are essential.
  • Immediate referral to a hand specialist should be considered for any patient presenting >24 hours after the initial injury, for those who have infected wounds, and for those who have sustained injury to the tendon, capsule, joint, or bone.
Special Therapy
Physical Therapy
  • Physical therapy is not necessary in the acute period.
  • At 1 week after treatment, ROM exercises should be started to prevent stiffness (especially of the MCP joints).
Medication (Drugs)
First Line
  • More than 40 bacterial species have been isolated from infected bite wounds.
  • The most common organisms are Eikenella corrodens and group A Streptococcus species in human bite wounds and Pasteurella multocida, S. aureus, and Bacteroides in animal bite wounds.
  • Augmentin provides satisfactory coverage for all organisms.
  • Treat infection empirically with intravenous antibiotics for 48 hours, then adjust based on cultures.
Surgery
  • Irrigation and debridement consist of cleaning infected tissues and removing devitalized tissues.
  • Cultures should be obtained.
  • Wounds should be left open and managed with dressing changes.
  • Extensor tendon injury should not be repaired until infection resolves.
Follow-up
Prognosis
Prognosis usually is good if infection is avoided or treated early.
Complications
  • Infection: Both soft tissue and bone
  • Stiffness
  • Pain
  • Extensor tendon injury
Patient Monitoring
  • At 24 hours, the packing should be changed.
  • The patient should be followed closely until the wound shows satisfactory healing with no evidence of infection.
  • When doubt exists about the stability of the wound, the patient should be followed at 24-48-hour intervals. 
Miscellaneous
Codes
ICD9-CM
882.1 Wound hand complicated
 
Patient Teaching
  • Patients are instructed in cases of open wounds to watch for signs of infection.
    • Open packing
    • Soaking
    • ROM
    • Redness
    • Pain
    • Fever
    • Drainage
    • Inability to move finger
FAQ
Q: What are the most important treatment interventions in a bite to the hand?
A: The 1st priority is prevention of infection, which consists of prompt surgical exploration with irrigation and debridement of the joint and treatment with intravenous antibiotics.
 
Q: When should an extensor tendon laceration secondary to a bite wound be repaired?
A: In this setting, repair of the extensor tendon can be delayed 7-10 days until the infection is resolved.

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