Association between long periods without high-speed workouts and risk of complete humeral or pelvic fracture in thoroughbred racehorses: 54 cases (1991-1994).
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.


METHODS
Reprospective study.


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


METHODS
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 > 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).


CONCLUSIONS
Risk of humeral fracture may be reduced if horses are cautiously reintroduced into race training after lay-up.
Carrier
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J. D. Wheat Orthopedic Research Laboratory, Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California, Davis 95616-8732, USA.
Estberg
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Stover
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Gardner
I A
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Johnson
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BJ
Read
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Ardans
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AA
D000818:Animals; D016022:Case-Control Studies; D016001:Confidence Intervals; D018592:Cross-Over Studies; D005260:Female; D006620:Hip Fractures / Q000209:etiology / Q000662:veterinary*; D006736:Horses / Q000293:injuries* / Q000502:physiology; D006810:Humeral Fractures / Q000209:etiology / Q000662:veterinary*; D008297:Male; D010384:Pelvic Bones / Q000293:injuries*; D010805:Physical Conditioning, Animal / Q000502:physiology; D012189:Retrospective Studies; D012306:Risk; D012307:Risk Factors; D013997:Time Factors