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

The study reviewed how varied diagnostic imaging methods were used to identify and treat a rare and serious bone infection in a four-month-old Thoroughbred filly.

Context and Clinical Presentation

• The study presents a case of a young Thoroughbred filly that had severe lameness in her left forelimb that had lasted for 24 hours.
• The condition causing the lameness was diagnosed as septic apophysitis of the proximal humerus – a rare, serious and infectious condition affecting the growth plate region of a horse’s upper arm bone. This condition caused abnormal bone and joint development evident in the filly’s shoulder.

Diagnostic Procedures Used

• The initial diagnosis was done using radiographic projections, which revealed mild irregularities and hardening of the proximal humeral growth plate region.
• An ultrasonographic examination followed, showing an abnormal increase in synovial fluid (the lubricating fluid in joints) within the intertubercular bursa (a sac-like cavity near the shoulder joint) and scapulohumeral joint (the joint connecting the arm to the shoulder blade). The ossifying bone surface in the intermediate tubercle of the humerus also showed irregularities.
• A Computed Tomographic (CT) examination concluded the diagnostic steps, revealing a hypoattenuating circle (an area appearing less dense or ‘lighter’ on the scan) at the site of the humeral growth plate region.

Importance of CT Imaging in this Case

• CT imaging proved essential for early identification of the infectious foci – the specific location of the infection. The others imaging modes did provide crucial information but did not pinpoint the exact location of the infection.
• This process subsequently enabled a sample to be extracted under ultrasound guidance from the infection site to allow for targeted antibiotic therapy – the precise tailoring of antibiotics to effectively combat the infection in the filly.

Treatment and Conclusion

• The precise identification of the infection allowed for targeted antibiotic therapy- an approach where antibiotics are specifically matched to the identified bacterial infection.
• This case study thus demonstrated the utility of multimodal diagnostic approaches in veterinary medicine, and the significance of CT imaging in such rare cases.