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The Relationship Between Radiographic Changes and Performance Outcomes in Cutting Horses

Take Home Message

Radiographic repositories are commonly used as a predictor of future performance outcome. This study found that many radiographic changes were not correlated with performance outcomes. Of particular note, no radiographic changes of the medial femoral condyle of the stifle, including grade 4 subchondral cystic lesions, were associated with decreased performance outcome. However, some mild radiographic changes, most specifically mild osteophytosis of the distal tarsal joints, were associated with decreased performance outcomes.

Introduction

Radiographic repositories are become increasingly popular in multiple disciplines as a screening tool prior to sale. However, the importance of the radiographic findings must be objectively assessed relative to potential significance. While studies have been done to correlate survey radiographic findings with performance outcomes in Thoroughbreds, no such published study exists in Quarter Horses. This paper serves as part two of a study performed by Dr. Myra Barrett (as part of an M.S.) with Drs. Park and McIlwraith examining the relationship between radiographic changes in survey radiographs relative to objective performance outcomes in Quarter Horse cutting horses.

The goal of this study is to better clarify the potential significance of radiographic changes on repository radiographs relative to performance. This in turn will allow veterinarians and their clients to make more objective, informed decisions prior to purchase about the potential implications of various radiographic changes.

Methods: Radiographic changes of 436 Quarter Horses, which were quantified in a previous paper (Contino et al. 2011), were compared to objective performance outcome parameters. The parameters were: 1) likelihood of competing, 2) likelihood of earning money as a three year old, four year old, and as a three and four year old combined, 3) average amount of money earned as a three year old, four year old, and as a three and four year old combined. Mailed questionnaires and phone calls to owners of horses that did not earn money were used to try to determine why the horse had no recorded earnings.

Figure 1 (above). Osteophytes in the tarsus were recorded by joint and bone involved and graded by size. A very small osteophyte (Grade 1) on the distolateral aspect of the central tarsal bone (A), a small osteophyte (Grade 2) on the proximal dorsolateral aspect of the third metatarsal bone (B), a medium osteophyte (Grade 3) on the distomedial aspect of the central tarsal bone (C) and a large osteophyte (Grade 4) on the proximal dorsolateral aspect of the third metatarsal bone (D) are shown with arrows. Reproduced with permission from Contino et al. (2011).

 

Results

When the tarsometatarsal (TMT) and distal intertarsal (DIT) joints were examined together (Fig. 1), the presence of mild (grade 2) osteophytes, which affected 19% of the horses, was associated with reduced chance of competing, earning money and mean money earned. Very mild and mild osteophytes of the third and central tarsal bone assessed individually at the level of the TMT and DID also have some significant effects in multiple performance outcome categories. The presence of thickening of the dorsal cortex of hind second phalanx as well as osteophytes as this location was associated with an increased likelihood of earning money. Several other potentially significant findings are reported but affect a relatively small number of the horses included in the study. Radiographic changes of the medial femoral condyle of the stifle were not significantly associated with performance outcome.

Conclusions

Many radiographic changes were not found to be significantly associated with performance outcome. However, some mild changes were associated with decreased performance. In addition, some radiographic changes were correlated with improved performance outcome. The findings of this study can be used to help veterinarians make more objective assessments of survey radiographic findings prior to sale. This research helps lay the groundwork for further investigations of the significance of survey radiographic findings in individual breeds and disciplines.

Acknowledgements

Thank you to Dr. Sangeeta Rao for her statistical analysis and to Taryn Yates for her assistance with data collection.

References

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