Cervical Vertebral Osteomyelitis With Secondary Septic Arthritis of the Atlantoaxial Joint in a Foal: A Case Report

A 36-day-old, 100-kg Thoroughbred colt was presented with a sudden onset of abnormal head carriage and pyrexia. Radiography revealed an osteomyelitis of the vertebral body of the second cervical vertebra. Ultrasonography revealed abscessation in the region of the atlantoaxial articulation on the left side, and fluid aspirated from the abscess confirmed suppurative inflammation. Surgical management was not feasible on economic grounds, and therefore this case was managed with aggressive medical therapy based on the most likely pathogens involved. To provide prolonged antibiotic therapy within the client’s budget, the antibiotic flucloxacillin (Staphlex, 500 mg) was used at a dose of 10 mg/kg by mouth, three times daily. Thirty-eight days after first presentation, the foal was euthanized because of chronic pain and deterioration in neurologic signs. A diagnosis of chronic osteomyelitis of the body of the second cervical vertebra (axis) was made with concurrent septic arthritis of the atlantoaxial joint involving the articular surface of the first cervical vertebra (atlas) and cervical myelopathy of the spinal cord within the first two vertebrae. No pathogens were isolated post mortem. This is the first report to describe the use of flucloxacillin in a foal. Although the outcome was fatal, the medical therapy provided could be considered successful at sterilizing the bony lesion.