title: Association between long periods without high-speed workouts and risk of complete humeral or pelvic fracture in thoroughbred racehorses: 54 cases (1991-1994).
abstract: 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.
authors.affiliation: J. D. Wheat Orthopedic Research Laboratory, Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California, Davis 95616-8732, USA.
authors.forename: T K
authors.initials: TK
authors.lastname: Carrier
authors.forename: L
authors.initials: L
authors.lastname: Estberg
authors.forename: S M
authors.initials: SM
authors.lastname: Stover
authors.forename: I A
authors.initials: IA
authors.lastname: Gardner
authors.forename: B J
authors.initials: BJ
authors.lastname: Johnson
authors.forename: D H
authors.initials: DH
authors.lastname: Read
authors.forename: A A
authors.initials: AA
authors.lastname: Ardans
mesh_terms: 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