Radiography and Standing Computed Tomography of an Osteochondritis Dissecans Lesion Found at the Dorsodistolateral Aspect of the Calcaneus in a 3-Year-Old Horse.

The research article discusses the identification of an unusual osteochondritis dissecans (OCD) lesion in the bone of a 3-year-old horse’s foot, and how radiography and standing computed tomography were used to locate and evaluate this lesion.

The Case and Detection

In the paper the researchers were conducting a pre-purchase examination of a 3-year-old Freiberger stallion when they discovered an unexpected OCD lesion in the horse’s left tarsus, which is equivalent to the human ankle.

• Osteochondritis dissecans (OCD) is an abnormality in joint cartilage and underlying bone that generally causes pain and restricts movement.
• It was incidental because it wasn’t the main reason the horse was being examined. The researchers came across it by chance while conducting a different health check.

Imaging Techniques

To inspect the lesion more closely, the team used two imaging techniques: radiography and computed tomography (CT).

• Radiography, also known as X-ray imaging, was used initially. The paper notes that certain projections were more effective at visualizing the lesion than others.
• The standing computed tomographic examination, or standing CT scan, confirmed that the damage was to a particular portion of the calcaneus, a large bone found in the foot. This kind of CT scan has the advantage of allowing vets to visualize the horse’s anatomy in detail while it is standing, rather than needing to lie down or be under anesthetic.

Findings and Recommendations

Based on the findings of this case, the authors suggest adjustments to the standard protocol for OCD screenings in horses.

• A dorsoplantar projection of the tarsus should be included for a better localization of suspected OCD lesions at the distal aspect of the talus or calcaneus.
• They also pointed out that CT scans allow for a much more detailed evaluation of OCD lesions, in particular this one which originated from a part of the equine tarsus that had not been previously described.