Race- and course-level risk factors for fatal distal limb fracture in racing Thoroughbreds.
ABSTRACT Considerable variation in the rates of equine fatality at different racecourses draws attention to probable risk factors at the level of course or race that might be partly responsible. Distal limb fractures are the most common cause of equine fatality on UK racecourses and identification of risk factors for such injuries and subsequent implementation of intervention strategies could significantly reduce the total number of racecourse fatalities.
To identify race- and course-level risk factors for fatal distal limb fracture in Thoroughbreds on UK racecourses.
A case-control study design was used. Case races were defined as those in which one or more horses sustained fatal fracture of the distal limb. Controls were selected in 2 different ways. Firstly, 3 races in which no fracture occurred were selected from all races of the same type held within 5 days of the case race (Analysis 1). Secondly, 3 control races were selected for each case race from all races of the same type held in the same year (Analysis 2). One hundred and nine cases were included in the study. Information about the race and the racecourses was collected from Computer Raceform. Conditional logistic regression was used to identify the relationship between a number of independent variables and the likelihood of fracture in a race.
Longer races with a larger number of runners were more likely to contain a fracture. Firmer going and fewer days since the last race on the same course were associated with an increased risk of fracture. The going at the course at the previous race meeting was also associated with the likelihood of fracture.
Modifications to the going on the day of a race and greater emphasis on ground maintenance between race meetings may have an impact on the risk of fatal distal limb fracture during racing.
Modification of risk factors such as the going and number of days since the last race meeting could reduce the number of equine fatalities on UK racecourses. The condition of the racecourse may be an important risk factor and future research should focus on the identification of course maintenance techniques that produce the safest possible racing surfaces.
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ABSTRACT: There is a substantial paucity of studies concerning musculoskeletal injuries in harness Standardbred racehorses. Specifically, little is known about the epidemiology of exercise-related musculoskeletal injuries. Most studies on this subject involve Thoroughbred racehorses, whose biomechanics and racing speed differ from Standardbred, making comparisons difficult. Here, a population of Standardbred racehorses trained at the same racecourse was studied over four years and a classification system for exercise-related musculoskeletal injuries was designed. The incidence rates of musculoskeletal injuries causing horses' withdrawal from training for 15 days or longer were investigated. A mixed-effects Poisson regression model was used to estimate musculoskeletal injury rates and to describe significance of selected risk factors for exercise-related injuries in this population. A total of 356 trotter racehorses from 10 different stables contributed 8961 months at risk of musculoskeletal injuries. Four-hundred-and-twenty-nine injuries were reported and classified into 16 categories, based on their aetiology and anatomical localisation. The overall exercise-related injury rate was 4.79 per 100 horse months. When considering risk factors one by one in separate univariable analyses, we obtained the following results: rates did not differ significantly between genders and classes of age, whereas one driver seemed to cause fewer injuries than the others. Racing speed and racing intensity, as well as recent medical history, seemed to be significant risk factors (p < 0.001), while being shod or unshod during racing was not. On the other hand, when pooling several risk factors in a multivariable approach, only racing intensity turned out to be significant (p < 0.001), since racing speed and the racing intensity were partially confounded, being strongly correlated to one another. Characterizing epidemiology of exercise-related musculoskeletal injuries in trotter racehorses provides baseline incidence rate values. Incidence rates of stress fracture are lower in Standardbreds compared to Thoroughbreds, whereas the opposite is true for tendon and suspensory ligament injuries. In addition to identification of risk factors for musculoskeletal injuries among Standardbred racehorses, results suggest that racing intensity seems to be a protective predictor of risk and recent medical history could be used to identify horses at risk of injury.BMC Veterinary Research 01/2014; 10(1):11. · 1.86 Impact Factor
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ABSTRACT: A retrospective cohort study of distal limb fracture and superficial digital flexor tendon (SDFT) injury in Thoroughbred racehorses was conducted using health records generated by the British Horseracing Authority (BHA) between 2000 and 2010. After excluding records of horses that had both flat and jump racing starts, repeated records were reduced to a single binary record per horse (n = 66,507, 2982 sires), and the heritability of each condition was estimated using residual maximum likelihood (REML) with animal logistic regression models. Similarly, the heritability of each condition was estimated for the flat racing and jump racing populations separately. Bivariate mixed models were used to generate estimates of genetic correlations between SDFT injury and distal limb fracture. The heritability of distal limb fracture ranged from 0.21 to 0.37. The heritability of SDFT injury ranged from 0.31 to 0.34. SDFT injury and distal limb fracture were positively genetically correlated. These findings suggest that reductions in the risk of the conditions studied could be attempted using targeted breeding strategies.The Veterinary Journal 01/2014; · 2.42 Impact Factor
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ABSTRACT: Musculoskeletal injuries are a common cause of lost training days and wastage in racehorses. Many bone injuries are a consequence of repeated high loading during fast work resulting in chronic damage accumulation and material fatigue of bone. The highest joint loads occur in the fetlock which is also the most common site of subchondral bone injury in racehorses. Microcracks in the subchondral bone at sites where intra-articular fractures and palmar osteochondral disease occur are similar to the fatigue damage detected experimentally after repeated loading of bone. Fatigue is a process that has undergone much study in material science in order to avoid catastrophic failure of engineering structures. The term fatigue life refers to the numbers of cycles of loading that can be sustained before failure occurs. Fatigue life decreases exponentially with increasing load. This is important in horses as loads within the limb increase with increasing speed. Bone adapts to increased loading by modelling to maintain the strains within the bone at a safe level. Bone also repairs fatigued matrix through remodelling. Fatigue injuries develop when microdamage accumulates faster than remodelling can repair. Remodelling of the equine metacarpus is reduced during race training and accelerated during rest periods. The first phase of remodelling is bone resorption which weakens the bone through increased porosity. A bone that is porous following a rest period may fail earlier than a fully adapted bone. Maximising bone adaptation is an important part of training young racehorses. However, even well adapted bones accumulate microdamage and require ongoing remodelling. If remodelling inhibition at the extremes of training is unavoidable then the duration of exposure to high speed work needs to be limited and appropriate rest periods instituted. Further research is warranted to elucidate the effect of fast speed work and rest on bone damage accumulation and repair.Equine Veterinary Journal 02/2014; · 2.29 Impact Factor