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

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Abstract

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.

Introduction

Osteomyelitis, often associated with septic arthritis, is a serious orthopedic condition in foals. Septic osteomyelitis is most often a result of hematogenous dissemination of bacteria with localization near the physeal growth plate in the metaphyseal or epiphyseal regions of bone [1]. Bacteria may gain access through the umbilicus or respiratory or gastrointestinal tract, resulting in a bacteremia. When IgG is routinely assessed and Hypermune equine plasma (Veterinary Immunogenics Ltd., Penrith, United Kingdom) is administered to foals with IgG <400 mg/dL, the cumulative incidence of osteomyelitis within the first 30 days is 0.2% [2]. In foals less than 6 months of age with septic osteomyelitis, the femur, distal phalanx, and tibia are the most commonly affected sites, accounting for 55% of cases [3]. Concurrent septic arthritis is present in 70% of foals of which 93% have osteomyelitis of bones adjacent to a septic joint [3]. Vertebral osteomyelitis is an uncommon condition in foals, most commonly affecting the cervical and lumbar regions of the spinal column [4]. An acute onset of pain or stiffness, sometimes with ill thrift, and neurological evidence of focal spinal cord compression with para or tetra paresis are strongly suggestive of vertebral osteomyelitis [4]. Multiple cases of vertebral body osteomyelitis in foals have been reported in the literature [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], but only one other case has been noted affecting the atlantoaxial joint [15]. Septic osteomyelitis is managed medically with appropriate antibiotics and surgically when access to the site of infection is possible. Medical therapy of vertebral osteomyelitis has previously been reported as unsuccessful [9], [10]. One case of osteomyelitis involving the second and third cervical vertebrae was successfully managed by surgical debridement and interbody fusion [14]. Described here is the medical treatment of osteomyelitis of the vertebral body of the second cervical vertebra (C2) of a foal with a secondary septic arthritis of the atlantoaxial (AA) joint.

Section snippets

Case Report

A 5-week (36-day)-old Thoroughbred colt (weight 100 kg) was presented with sudden-onset abnormal head carriage. The colt was nursing regularly for short periods but was struggling to keep up with its dam at walk. The colt had been born on the premises and had no history of illness. Routine examination for insurance performed at 2 days of age had detected no abnormalities, and measurement of IgG status at this time was adequate at >800 mg/dL. There was no history of systemic disease and no known

Discussion and Conclusion

This foal presented with signs of musculoskeletal pain, pyrexia, and a reduced range of movement consistent with a diagnosis of septic arthritis and osteomyelitis [18], [19]. The presence of localizing signs of heat, pain, and swelling in the region of the first two vertebrae was helpful in determining the site of the lesion, and neutrophilia and hyperfibrinogenemia, consistent with septic inflammation and tissue damage, were supportive of the diagnosis [9], [20]. Radiography confirmed the

Acknowledgments

The authors would like to thank Dr. Alan Julian of Gribbles Veterinary, Hamilton, New Zealand for assistance with the post mortem examination and histopathology.

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