Osteomyelitis in Small Animals
Inflammation and infection of the medullary cavity, cortex, and periosteum of bone are most frequently associated with bacteria such as Staphylococcus spp, Streptococcus spp, Escherichia coli,Proteus spp, Pasteurella spp, Pseudomonas spp, and Brucella canis. Anaerobic bacteria are less frequently isolated and may be part of a polymicrobial infection. Fungal diseases are based on geographic distributions and include Coccidioides immitis (southwestern USA), Blastomyces dermatitidis (southeastern USA), Histoplasma capsulatum (central USA), Cryptococcus neoformans, and Aspergillus spp (worldwide). Factors contributing to infection include ischemia, trauma, focal inflammation, bone necrosis, and hematogenous spread.
Clinical signs may be acute or chronic. Animals may have lameness, pain, abscessation at the wound site, fever, anorexia, and depression. Radiography can reveal bone lysis, sequestration, irregular periosteal reaction, loosening of implants, and fistulous tracts. Deep fine-needle aspiration, cytology, and blood cultures may also reveal evidence of infection.
Treatment includes both medical and surgical therapies. Long-term oral or injectable antibiotics such as clavulanic acid/amoxicillin (15 mg/kg, bid), cefazolin (30 mg/kg, bid), clindamycin (11 mg/kg, bid), enrofloxacin (15 mg/kg, bid), amikacin (15 mg/kg, bid), or oxacillin (22 mg/kg, tid) are used. Additionally, wound debridement, lavage, and removal of loose implants are recommended. Open or closed wound drainage and delayed autogenous, cancellous bone grafting can also be performed. In chronic, refractory cases, limb amputation may be warranted. Prognosis is variable and based on the severity and chronicity of the infection. Appropriate antimicrobial therapy based on bacterial culture and antibiotic sensitivity testing is mandatory for successful results.