New Insights into Spinal Bone Lesions Linked to Poor Performance in Horses

Osseous Pathologic Changes in the Thoracic Region of the Equine Vertebral Column in Horses Euthanized for Poor Performance

T. J. Spoormakers, J. P. R. Walmsley, C. M. Riggs, V. A. Barker, T. H. Witte

Background

The study investigates the role of osseous pathologic changes (OPCs) in the thoracic vertebral column—specifically in articular process joints (APJs) and the vertebral body—in Thoroughbred racehorses euthanased for poor performance. Despite growing interest in spinal kinematics, limited post-mortem data exist linking specific spinal lesions to athletic impairment. The goal was to quantify and describe these changes, offering a clearer understanding of their potential contribution to performance deficits.

Methods

A total of 49 Thoroughbred racehorses euthanased for poor performance underwent post-mortem examination. The thoracic spine from T5 to T18 was removed, radiographed, and evaluated macroscopically. OPCs in both APJs and vertebral bodies were assessed across the thoracic region using scoring systems for lesion severity and location. Intra- and interobserver reliability was tested to ensure consistency in lesion detection and grading.

Results

APJ lesions were widespread, found in 93.9% of horses, and peaked in frequency and severity at T15–T17. Vertebral body lesions were also common (71.4% of horses), mainly affecting the caudal thoracic vertebrae (T13–T18). Severe lesions in both APJs and vertebral bodies were often found in the same horses and in adjacent spinal locations. Radiography alone failed to detect a significant proportion of macroscopic lesions. Interobserver agreement was good for APJ lesion scoring but lower for vertebral body assessment.

Limitations

The study lacks a control group of horses euthanased for non-performance-related reasons, which limits the ability to determine if the OPCs are unique to poor performance. Additionally, biomechanical and functional correlations between lesion presence and clinical signs were not evaluated. Radiographic limitations and reliance on post-mortem data may have introduced observational bias.

Conclusions

OPCs in the thoracic spine are prevalent in Thoroughbreds euthanased for poor performance, particularly in the caudal thoracic region. These findings suggest a potential role for thoracic spinal pathology in athletic dysfunction. However, further comparative and functional studies are necessary to establish definitive clinical significance and causal relationships between OPCs and poor performance.

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