Multimodal Diagnostic Imaging to Identify Septic Apophysitis of the Proximal Humerus in a Thoroughbred Foal

A 4-month-old Thoroughbred filly was referred for evaluation of severe left forelimb lameness of 24 hours duration. Radiographic projections of the shoulder revealed mild irregularity and sclerosis of the proximal humeral apophysis. Ultrasonographic examination showed a moderate increase in the amount of anechogenic synovial fluid within the intertubercular bursa and scapulohumeral joint, and irregularity of the ossifying bone surface of the intermediate tubercle of the humerus. Computed tomographic (CT) examination revealed a circular hypoattenuating area at the level of the proximal apophysis of the humerus. CT imaging in this case was essential for an early identification of the septic foci and it allowed ultrasound-guided sample from the lesion for the selection of targeted antibiotic therapy.