Abstract
Reasons for performing study: To investigate the racing performance of Thoroughbred horses with osseous cyst-like lesions (OCLLs) in the distal phalanx causing lameness and treated conservatively.Objectives: To assess horses' ability to race and perform after radiographic identification of OCLL in the distal phalanx of Thoroughbred horses with lameness at the time of detection and undergoing conservative treatment.Study Design: Retrospective case control study.Methods: The clinical database of one equine clinic was reviewed in a 10-year period for Thoroughbreds showing lameness localized to the foot and a radiographic diagnosis of OCLL in the distal phalanx. Sex, age at time of detection of the OCLL, degree of lameness, affected limb, and treatment were recorded. Successful performance of horses was assessed by racing at least once after detection of the OCLL and maximum racing performance rating (RPR). Radiographic features such as size, location, sclerotic rim of the OCLL and irregularity of the articular surface of the distal phalanx were compared to successful performance using univariable statistical analysis. Successful performance of horses with OCLL was compared to a control group of maternal siblings by parametric testing.Results: Twenty-two horses met the inclusion criteria. Thirteen horses raced after the detection of OCLLs. Eight did not race, one case had not yet reached racing age, resulting in 62% (13/21) of racing age racing at least once. The number of successfully performing horses with an OCCL was significantly lower compared to their maternal siblings [p = 0.03, Odds ratio (OR) = 0.30]. If horses with OCLL in the distal phalanx raced, their RPR was similar to their maternal siblings. No significant association was found between radiographic features of OCLLs and successful performance, but OCLLs in the left forelimb carried a more favorable outcome for racing (p = 0.02, OR = 2.33 95%CI 1.27, 4.27) compared to OCLLs in any other limb.Conclusions: Horses with lameness and an OCLL in the distal phalanx managed conservatively are less likely to race when compared to their maternal siblings. If horses with OCLLs in the distal phalanx are able to race, their performance, measured as RPR, was comparable to their maternal siblings. Due to the small numbers in this study the results should be interpreted carefully.
Highlights
Lameness in racehorses results in welfare implications for the affected individual as well as in the loss of training days leading to poor performance and financial loss for owners
The OCLLs were identified in the forelimb in 17 horses and in the hindlimb in five horses
An OCLL was identified in the contralateral non-lame limb, both were affecting hindlimbs
Summary
Lameness in racehorses results in welfare implications for the affected individual as well as in the loss of training days leading to poor performance and financial loss for owners. In lame Thoroughbred racehorses, the veterinarian is expected to establish a diagnosis, which allows them to provide an accurate prognosis on racing performance, whilst choosing a cost effective, practical diagnostic tool, appropriate for use in an ambulatory setting. OCLLs may develop at various locations but are most commonly located adjacent to the articular surface, with or without a communication to the joint and often found at the center of the proximal aspect of the distal phalanx. Since they lack an epithelial lining, they are not considered as true bone cysts [13, 14]. The pathogenesis of such OCLLs is not completely understood, but a developmental disorder with failure of endochondral ossification, trauma, focal sepsis and/or ischemia, are considered as potential underlying pathomechanisms [15, 16]
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