Veterinary session

The thoracolumbar spine plays a vital role in orthopaedic problems in equine medicine. The vertebral column is very intricately constructed, and with slight morphologic alterations, it provides unique movement patterns in the separate segments of the spine. The examination of these structures is complex, and a definite diagnosis is often challenging to attain.

The computed tomography (CT) provides excellent visualisation of especially bony elements, and there have been significant developments in computer tomography of large animals in recent years, providing better images, allowing for scans of larger body parts and shortening the overall scanning time. However, with this imaging modality, little of the anatomy of the equine thoracolumbar spine is described.

This study reports a detailed reference of the CT-based anatomy of the healthy back in horses.

The CT was performed in four post-mortem specimens, three of which were reduced in size and only the thoracolumbar region with the proximal aspect of the rib cage was scanned. One of the CT scans was accomplished with the specimen completely intact, which we have not found in the literature before. A helical 16-slice multislice scanner with a 90 cm diameter gantry was used; the slices were set at a thickness of 2.0 mm, 135 kV and 450 mA with an exposure time of 0.75 s per rotation. The images were paired with corresponding anatomical sections and evaluated side by side. The assessment was done from the cranial thoracal (Th6 in three specimens and Th1 in one) to the last lumbar vertebrae (L6), emphasising the bony structures.

The vertebrae were excellently detailed in the bone window setting, and cortical and spongiform bone were well differentiated. In the size-reduced carcasses, soft-tissue visualisation was restricted. While the CT examination is still limited by the contrast in the patient's size and the gantry's aperture, our procedure with caudal and cranial positioning allows for a full-body scan of the entire spine in a medium-size adult horse.

Under general anaesthesia, CT of the equine spine can be of great diagnostic value for pathological disorders. Images obtained in this study may be used as a reference for CT anatomy of the thoracolumbar spine in horses. This field would tremendously benefit from further, more expansive studies, especially to describe anatomical variations and pathological changes.