Robert J. Mccarthy,     North Grafton, Massachusetts

Initial Assessment and Emergency Management

Treatment of an open fracture should be started at home. Owners are instructed to minimize all limb manipulation and to cover the wound and exposed bone with a sterile dressing if possible. A clean cloth or diaper is an appropriate alternative if bandage materials are not available. Owners should be warned that injured animals may bite, and they should consider placing a muzzle if necessary. Compression is usually sufficient to control hemorrhage during transport to the hospital.

Initial veterinary management is directed toward evaluation and treatment of other potentially life-threatening injuries and pain management, unless the wound is inadequately covered or is hemorrhaging profusely (Box 18-1). In this situation a sterile dressing and pressure wrap should be applied. Ligation of actively bleeding vessels is occasionally required. Protruding bone should not be forced back into the wound at this time since this allows additional contamination of the fracture site.

Evaluation of the stabilized patient begins with a thorough case history. Owners are questioned regarding the cause of the injury and the environment in which the injury occurred. Whether the animal was “run into” or “run over” is significant because in the latter situation a substantial crushing component is more likely. The environment where the injury occurred may help determine potential wound contaminants and dictate the choice of future antibiotic therapy.

Initial wound evaluation should be directed toward a careful assessment of the neurologic and vascular status of the limb because these findings may alter treatment options. Simple diagnostic tests include clipping a toenail short to check for active bleeding, evaluation of extremity pulses distal to the wound by palpation or by Doppler flow detection, limb temperature assessment, and patient recognition of extremity sensation. Although the degree of wound contamination and apparent soft and bony tissue trauma should be determined, limb manipulation must be minimized and wound probing avoided because these procedures increase contamination, cause vascular damage, and result in pain. Potential problems associated with small puncture wounds should not be underestimated because debris may be under the skin, deep in the wound and medullary cavity. Preliminary deep wound cultures should be obtained at the time of initial wound evaluation. In humans 50% to 70% of open fractures produce positive results when cultured at presentation, and in 66% of cases the bacteria cultured at presentation are the same as those later isolated from infected wounds. After the wound is assessed and cultured, radiographs are obtained and a more functional immobilization dressing is applied. The purpose of this bandage is to prevent additional contamination, preserve vasculature, and decrease pain. Most organisms that are recovered from the wound after the development of an orthopedic infection can be traced to the hospital; thus early protection of the wound is critical. Sterile dressings should be used in all cases and strict asepsis maintained. A splint is generally applied to support open fractures below the elbow or stifle, whereas a spica-type bandage is required to immobilize fractures more proximal on the limb. Fractures proximal to the elbow or stifle are frequently difficult to immobilize properly, and in many cases it may be preferable simply to cover the wound and confine the animal to a small cage.

Antibiotics are always indicated for animals with open fractures because all wounds are contaminated and wounds that occurred longer than 6 to 8 hours before definitive surgical débridement and lavage are infected. In humans antibiotics administered within 3 hours of injury significantly decrease the rate of future wound infection. Risk of infection may be greater in animals with open fractures because of decreased host defense mechanisms caused by stress or because of vascular compromise. Choice of antibiotic is based on the cause of injury, nature of the wound, likely bacterial contaminants, and knowledge of commonly isolated bacteria from patients with osteomyelitis. Staphylococcus spp. cause between 50% and 60% of bone infections in dogs, and many of these infections are monomicrobial. In general, concerns about penetration of antibiotics into bone interstitial fluid are unfounded.

First-generation cephalosporins such as cefazolin (Kefzol, 20 mg/kg q8h) are often the initial drugs of choice because they are broad spectrum, can be given intravenously, are usually effective against β-lactamase–producing Staphylococcus spp., and are relatively inexpensive. If contamination with a gram-negative organism is expected, a fluoroquinolone antibiotic such as enrofloxacin (Baytril, 5 to 10 mg/kg SC q24h) or a penicillin-derivative such as imipenem (Primaxin, 5 to 10 mg/kg IV q6-8h) may be added. Anaerobic infections are more common than previously thought, and clindamycin (Antirobe, 5 to 10 mg/kg PO q12h) or metronidazole (Flagyl, 25 to 40 mg/kg PO q12h) should be considered in addition to first-generation cephalosporins in animals with severely necrotic, avascular wounds. The initial choice of antibiotic is altered when culture and sensitivity test results become available. In type I and II open fractures that are not infected, antibiotic use can be discontinued immediately after fracture repair. In any type III open fracture or in type I or II open fractures that are infected, more prolonged use is indicated. In general, antibiotic therapy is continued for about 1 month in these cases. Antibiotics can be discontinued at that time if there is no clinical or radiographic evidence of infection.

Recognition of pain is difficult in dogs and cats because even animals with severe pain may show no overt clinical signs. Open fractures are associated with extensive pain and anxiety in humans, and a similar situation is expected in animals. Pain should be treated with narcotic analgesics (see Chapter 12). Buprenorphine (Buprenex, 0.01 to 0.02 mg/kg IV or IM q6-8h), hydromorphone (Dilaudid, 0.05 to 0.2 mg/kg IV, IM, or SC q2-6h), methadone (Methadone hydrochloride, 0.1 to 0.3 mg/kg IV, IM, or SC q2-6h), and fentanyl (Sublimaze, 2 to 10 µg/kg/hr constant rate infusion [CRI] for dogs; 1 to 3 µg/kg/hr for cats CRI) all provide good analgesia, although fentanyl may be best for severe pain. A dermal fentanyl patch may be an adjunct for providing longer-term analgesia but should not be used in animals with poor peripheral perfusion because absorption will be unreliable. Fentanyl patches should also not contact heating pads because absorption may be increased to a level causing toxicity.