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Abstract

Objective

To investigate the relation between several racing speed history characteristics and risk of fatal skeletal injury (FSI) in racing Thoroughbreds.

Animals

64 Thoroughbreds euthanatized during a 9-month period in 1991 at a California racemeet because of a catastrophic fracture incurred while racing (cases), identified retrospectively. For each race in which an FSI occurred, 1 control horse was randomly selected from the noncatastrophically injured participants.

Procedure

Racing and officially timed workout histories were obtained for each horse. Several history characteristics were calculated to summarize racing career patterns and high-speed exercise schedules prior to date of injury and included age at first race, proportion of career spent laid up, average duration of laid up periods, average lifetime racing frequency, time from last lay up to date of injury, and total and rate of distance accumulated 1 to 6 months prior to date of injury. History characteristics associated with FSI were screened by paired t-test and studied in detail using conditional logistic regression.

Results

High total and high average daily rates of exercise distance accumulation within a 2-month period were associated with higher risks for FSI during racing, yet career patterns, such as age at first race or total proportion of career spent laid up, were not found to be associated with risk for FSI. A horse that had accumulated a total of 35 furlongs of race and timed-work distance in 2 months, compared with a horse with 25 furlongs accumulated, had an estimated 3.9-fold increase in risk for racing-related FSI (95% confidence interval = 2.1, 7.1). A horse that had accumulated race and timed-work furlongs at an average rate of 0.6 furlong/d within a 2-month period, compared with a horse with an average of 0.5 furlong/d, had an estimated 1.8-fold increase in risk for racing-related FSI (95% confidence interval = 1.4, 2.6).

Conclusions and Clinical Relevance

Thoroughbred racehorses that either accumulate large total highspeed distances or rapidly accumulate high-speed distances within a 2-month period may be at increased risk for FSI during racing. (Am J Vet Res 1996;57:1549–1555)

Free access
in American Journal of Veterinary Research

Objective

To determine whether a two-month or longer period without official high-speed workouts (lay-up) is associated with humeral or pelvic fracture in Thoroughbred racehorses.

Design

Retrospective study.

Animals

Thoroughbred racehorses in California that were euthanatized because of a complete humeral or pelvic fracture.

Procedure

Age, sex, activity, number of lay-ups, number of days from a race or official timed workout to fracture, number of days from end of last lay-up to fracture, mean duration of lay-ups, and total number of days in race training were compared between horses with humeral fractures and horses with pelvic fractures. A case-crossover study was used to estimate relative risk for fracture of the humerus or pelvis occurring within hazard periods of 10 and 21 days following lay-up, compared with periods following more regular participation in official racing or timed workout events.

Results

Horses with pelvic fractures were more often female, older, and had 0 or ≥ 2 lay-ups. Horses with humeral fractures were typically 3-year-old males that had 1 lay-up. Horses with pelvic fractures had more total days in race training, fewer days from last exercise event to fracture, and a greater number of days from end of last lay-up to fracture than horses with humeral fractures. Return from lay-up was strongly associated with risk for humeral fracture during hazard periods of 10 and 21 days (relative risk = 71 and 45, respectively).

Clinical Implications

Risk of humeral fracture may be reduced if horses are cautiously reintroduced into race training after lay-up. (J Am Vet Med Assoc 1998;212: 1582–1587)

Free access
in Journal of the American Veterinary Medical Association

Objective

To investigate relationships of several racehorse characteristics and race conditions with risk of a catastrophic musculoskeletal injury (CMI) resulting in euthanasia in Thoroughbreds during racing in California in 1992.

Design

Retrospective longitudinal study.

Animals

Thoroughbreds that incurred CMI during racing and all California race entrants in 1992.

Procedure

Necropsy records were reviewed, and race start information was obtained. Incidence risk of CMI/1,000 race entrants was estimated. Relationships between CMI during racing and race-meet, entrant age and sex, race type and length, and racing surface type and condition were evaluated by use of logistic regression.

Results

Incidence risk of CMI was 1.7/1,000 entrants. A higher risk of CMI was found at 2 fair race-meets, with incidence risks of 4.9 and 5.5/1,000 entrants. Risk of injury in male horses was 1.7 times greater than that in female horses, and influence of age on risk depended on race type. Risk of injury for horses 2 to 5 years old was two times greater for claiming horses than for maiden horses. Race length or racing surface type (dirt vs turf) or condition (fast, muddy, yielding) were not significantly associated with risk of CMI.

Clinical Implications

Incidence of CMI was similar among 12 of 14 major and fair race-meets and among various race lengths and racing surface types and conditions, whereas incidence of CMI was influenced by entrant age and sex as well as race type. Investigators should consider controlling for age and sex, race-meet, and race type whenever possible in studies of risk of CMI. (J Am Vet Med Assoc 1998; 212:544-549)

Free access
in Journal of the American Veterinary Medical Association

Objective

To characterize and contrast data from Thoroughbreds that incurred a fatal musculoskeletal injury ( fmi; injury resulting in death or euthanasia) during racing or training and data from all California race entrants during a 9-month period in 1991.

Design

Case-control study.

Animals

Thoroughbreds that incurred a fmi during racing or training at a California race-meet and all California race entrants from January through June and October through December 1991.

Procedure

Age and sex were compared with χ2 and Fisher's exact tests among horses fatally injured while racing and training. A log-linear model was fit to assess the relationship between race-meet and age and sex of California race entrants. Incidence risk of racing fmi was estimated per 1,000 race entrants, and the relationship between the occurrence of fmi during racing with race-meet, age, and sex was evaluated by logistic regression.

Results

Injury type and sex-specific age distributions differed among the horses fatally injured during racing and training. Age and sex distributions of the race entrants were not independent and varied among race-meets. Overall incidence risk of racing fmi was estimated at 1.7/1,000 race entrants. Risk of racing fmi in male horses was about twofold that in female horses, and in 4-year-olds was twofold that in 3-year-olds.

Clinical Implications

Age- and sex-related differences in risk of incurring a fmi during racing should be considered when comparing fatal injury rates among race-meets.

Free access
in Journal of the American Veterinary Medical Association