Reasons for performing study: Ultrasonographic (US) abnormalities of the suspensory ligament branch (SLB) have been poorly investigated but can have considerable impact on market value and career path when encountered in athletic horses. There is a need for determination of the prevalence and relationship to clinical injury of these US abnormalities in the Thoroughbred (TB) racehorse.
Objectives: To establish the prevalence of, and the repeatability of an US grading system for, subclinical US abnormalities of the forelimb SLB in a population of UK TB flat racehorses.
Methods: Ultrasonographic assessment of the forelimb SLBs of 60 TB racehorses free from history and clinical indication of SLB desmopathy in a single UK training yard was performed. Images were viewed independently by 2 blinded observers and graded for US abnormality. Interobserver agreement was assessed using Cohen's kappa statistic with 95% confidence intervals (95% CI).
Results: Prevalence of horses with subclinical US abnormality of the forelimb SLB of moderate severity was 6.7%. Medial branches were overrepresented. Inter observer agreement was substantial for US grade (kappa = 0.743; 95% CI 0.652–0.834) and almost perfect for appearance of sesamoid bone at ligament insertion (kappa = 0.817; 95% CI 0.66–0.98).
Conclusions: The study reveals that a proportion of TB racehorses in flat training free from history or clinical signs of SLB injury have US abnormalities that could negatively impact on market value and career path.
Potential relevance: Clinicians should be aware that US abnormalities of the SLB may not always be related to clinical desmopathy. Further longitudinal studies are required to determine whether such findings are predictive for future injury.