Humeral stress remodelling locations differ in Thoroughbred racehorses training and racing on dirt compared to synthetic racetrack surfaces.

The research article examines the impact of different racetrack surfaces, dirt and synthetic, on the stress remodelling locations in the humeral bone of Thoroughbred racehorses, and also assesses the possible usefulness of scintigraphy in this context.

Objective and Methodology

The objective of the study was to ascertain differences in the severity and location of stress remodelling in the humerus of Thoroughbred racehorses when evaluating dirt and synthetic racetrack surfaces. The researchers also sought to explore the potential implications of these different remodelling locations and to assess the potential use of scintigraphy, a diagnostic imaging technique, for preventing complete humeral fractures.

• The researchers reviewed scintigraphic images of humeri from 841 Thoroughbred racehorses at three racetracks over an interval of two years, before and after switching from dirt to synthetic surfaces.
• The images were examined for the location and severity of lesions, with the potential influence of the surface change on lesion distribution being investigated using statistical measures such as the Chi-square or Fisher’s exact tests.
• Moreover, previously fractured humeri were also analyzed to understand the location and severity of stress remodelling associated with complete fracture.
• To ascertain if racehorses with scintigraphic lesions suffered humeral fractures and if those with a complete humeral fracture had undergone a scintigraphic examination, relevant databases were queried.

Results

The study yielded several noteworthy findings.

• On synthetic track surfaces, racehorses had more of distal humeral lesions, while on dirt surfaces, they had a greater proportion of caudoproximal lesions.
• Proximal lesions were found to be more severe than distal ones.
• Most complete fractures were associated with caudoproximal lesions, which were significantly more severe than distal lesions.
• Interestingly, none of the horses with a scintigraphic lesion ended up with a complete humeral fracture and, conversely, none of the horses with a complete humeral fracture had previously undergone scintigraphic examination.

Conclusions

These findings establish that racing surface can affect the location of stress remodelling in humeri in horses. The severity of lesions is directly related to their location. The study found an association between complete humeral fractures and caudoproximal stress remodelling in the absence of scintigraphic examination.

• The study also indicated that the risk of complete humeral fracture may be lower on synthetic surfaces compared to dirt surfaces.
• By extension, the risk might be mitigated for horses that undergo scintigraphy, indicating potential preventative value of the technique in regard to humeral fractures.