Race- and course-level risk factors for fatal distal limb fracture in racing Thoroughbreds

REASONS FOR PERFORMING STUDY: 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. OBJECTIVES: To identify race- and course-level risk factors for fatal distal limb fracture in Thoroughbreds on UK racecourses. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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. POTENTIAL RELEVANCE: 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.     

Horse-level risk factors for fatal distal limb fracture in racing Thoroughbreds in the UK

REASONS FOR PERFORMING STUDY: Fractures below the level of the radius or tibia (distal limb fractures) are the most common cause of equine fatality on UK racecourses; however, little is known about their epidemiology or aetiology. Identification of risk factors could enable intervention strategies to be designed to reduce the number of fatalities. OBJECTIVES: To identify horse-level risk factors for fatal distal limb fracture in Thoroughbreds on UK racecourses. METHODS: A case-control study design was used. Fractures in case horses were confirmed by post mortem examination and 3 matched uninjured controls were selected from the race in which the case horse was running. One hundred and nine cases were included and information was collected about previous racing history, horse characteristics and training schedules. Conditional logistic regression was used to identify the relationship between a number of independent variables and the likelihood of fracture. RESULTS: Horses doing no gallop work during training and those in their first year of racing were at significantly increased risk of fracture on the racecourse. Case horses were also more likely to have trained on a sand gallop, i.e. a gallop described by trainers as being primarily composed of sand. CONCLUSIONS: Modifications to training schedules, specifically within the first year of racing, may have a large impact on the risk of fatal distal limb fracture on the racecourse. Horses should do some gallop work in training and our results suggest that the minimum distance galloped should be between 805-2012 m (4-10 furlongs)/week. POTENTIAL RELEVANCE: The information from this study can be used to alter training schedules in an attempt to reduce the incidence of fatal distal limb fracture in Thoroughbred racehorses. Training should include some gallop work, and further studies, recording the exact level of work, will help to identify an optimum range of training speeds and distances which will reduce the liklihood of catastrophic fracture on the racecourse.     

Effect of ‘tongue tie’ use on racing performance of Thoroughbreds in the United Kingdom

Reasons for performing study: There is contradictory published evidence on the potential efficacy of ‘tongue ties’ (TTs) for treatment of intermittent dorsal displacement of the soft palate (DDSP) in racehorses. Objectives: To evaluate the effect of TTs on racing performance in Thoroughbred racehorses in the UK using a retrospective cohort study. Methods: Data on individual horses' lifetime racing performance and TT use were retrieved from the Racing Post Online Database. Exposed cases were horses that ran with a TT in randomly chosen race meetings on one of 60 randomly chosen dates from 2001–2003. Unexposed (control) horses were matched to each exposed horse. Various measures of racing performance were analysed both within and between exposed and unexposed groups. Subsets of exposed horses that ran for 3 or 5 consecutive starts wearing TTs and their matched controls were analysed separately to examine the effect of repeated TT use. Results: The inclusion criteria were fulfilled by 108 horses. The odds ratio for ‘improvement’ in race earnings between exposed and unexposed horses was 1.85 for horses that ran at least once with a TT, and 3.60 and 4.24, respectively, for horses that ran in 3 or 5 consecutive races wearing a TT. After instigation of TT use, horses that ran in 3 or 5 consecutive races wearing a TT had a significant increase in earnings when they ran wearing a TT compared to their pre‐TT races. Conclusions and potential relevance: The use of a TT appears to have a beneficial effect on racing performance in a selected population of Thoroughbred racehorses.     

Effect of furosemide on performance of Thoroughbreds racing in the United States and Canada.

OBJECTIVE: To determine the effect of furosemide on performance of Thoroughbreds racing on dirt surfaces at tracks in the United States and Canada. DESIGN: Cross-sectional study. ANIMALS: All Thoroughbreds (n = 22,589) that finished a race on dirt surfaces at tracks in the United States and Canada between June 28 and July 13, 1997 in jurisdictions that allowed the use of furosemide. PROCEDURE: Race records were analyzed by use of multivariable ANOVA procedures and logistic regression analyses to determine the effect of furosemide on estimated 6-furlong race time, estimated racing speed, race earnings, and finish position. Principal component analysis was used to create orthogonal scores from multiple collinear variables for inclusion in the models. RESULTS: Furosemide was administered to 16,761 (74.2%) horses. Horses that received furosemide raced faster, earned more money, and were more likely to win or finish in the top 3 positions than horses that did not. The magnitude of the effect of furosemide on estimated 6-furlong race time varied with sex, with the greatest effect in males. When comparing horses of the same sex, horses receiving furosemide had an estimated 6-furlong race time that ranged from 0.56 +/- 0.04 seconds (least-squares mean +/- SE) to 1.09 +/- 0.07 seconds less than that for horses not receiving furosemide, a difference equivalent to 3 to 5.5 lengths. CONCLUSIONS AND CLINICAL RELEVANCE: Because of the pervasive use of furosemide and its apparent association with superior performance in Thoroughbred racehorses, further consideration of the use of furosemide and investigation of its effects in horses is warranted.     

Effects of furosemide on the racing times of Thoroughbreds

The effects of furosemide on the racing times of 79 horses without exercise-induced pulmonary hemorrhage (EIPH) and 52 horses with EIPH were investigated. Racing times were adjusted to 1-mile equivalent racing times by 2 speed handicapping methods, and analysis of covariance was used to adjust actual racing times by winning time and distance for each race. All 3 methods of determining racing time indicated that geldings without EIPH had significantly faster racing times (P less than 0.05) when given furosemide before racing than when furosemide was not given before racing. Females and colts without EIPH were determined to have faster racing times when furosemide was given before racing, but the difference was not significant. Geldings with EIPH had significantly faster racing times (P = 0.0231) when given furosemide before racing, as determined by one of the speed handicapping methods. There was a strong correlation (range 0.9314 to 0.9751) between the 1-mile equivalent racing times, as determined by the 2 speed handicapping methods for horses with and without EIPH. Furosemide failed to prevent the development of EIPH in many horses that were previously considered to be EIPH-negative. When given furosemide, 62 (25.3%) of 235 EIPH-negative horses were EIPH-positive after racing. Furosemide had questionable efficacy for prevention of EIPH in known EIPH-positive horses. Thirty-two (61.5%) of 52 EIPH-positive horses given furosemide before a race remained EIPH-positive after that race.     

Dermatomyositis in five Shetland sheepdogs in the United Kingdom

Five cases of dermatomyositis in four Shetland sheepdog puppies and one adult bitch are described. The dogs all had well-defined patches of scaling, crusting and alopecia over the muzzle, periorbital skin and distal limbs, and the tail, perineum and pinnae were affected in some of them. The affected puppies were all sired by the same stud dog. The affected adult bitch was unrelated to the puppies. Three of the four dogs tested had high serum creatine kinase concentrations and electromyographic abnormalities were detected in three of the four dogs tested. The histological changes observed in the skin of four of the dogs strongly supported the diagnosis of dermatomyositis, and in the fifth dog they were compatible with this diagnosis. Two of the puppies were euthanised shortly after being diagnosed. In the other two puppies and the adult the disease remains stable and non-progressive 15 to 18 months after diagnosis. The sire of the four affected puppies has been used extensively because it was considered to be genetically clear of collie eye anomaly.     

Conservative treatment of intra-articular distal phalanx fractures in horses not used for racing

OBJECTIVE: To determine the success rate and whether specific patient and treatment factors influenced the outcome after conservative treatment with a bar shoe with quarter clips of intra-articular fractures of the distal phalanx in horses not used for racing. DESIGN: Retrospective study. SAMPLE POPULATION: Thirty-two client-owned horses. PROCEDURE: Hospital records of horses that had been treated conservatively for intra-articular fractures of the distal phalanx at Skara Equine Hospital or Halland Animal Hospital in Sweden between 1995 and 2001 were reviewed. Racehorses in active training and horses affected with other musculoskeletal diseases were excluded from the study. Follow-up was performed by questionnaire and telephone inquires to the owners 1 to 7 years after injury. RESULTS: Twenty-two horses (69%) returned to their previous or expected level of use and did not wear their bar shoe when they were put back into training. There was no statistically significant correlation between outcome and patient or treatment variables, or bony union of the fracture. CONCLUSIONS AND CLINICAL RELEVANCE: Conservative treatment of intra-articular fractures of the distal phalanx carries a fair prognosis for return to previous or expected level of use in horses not used for racing. Radiographic evidence of fracture healing and age of the patient do not seem to influence the prognosis. Horses not used for racing do not need to be shod with a bar shoe with quarter clips for the rest of their athletic career.     

Assessment of prognosis for racing after carpal surgery in 210 Thoroughbreds

The efficacy of treating carpal lesions by arthrotomy was evaluated in 210 Thoroughbred racehorses, using survival analysis to compare their racing performances and earnings with those of 840 control horses. The treated horses were significantly inferior with respect to races contested, and wins plus places (P less than 0.001) and races won (P less than 0.01). There was no difference with respect to earnings (P less than 0.1); after adjusting for other factors, arthritis, site of fracture and presence of a displaced chip had no effect on racing performance in horses with a single-site lesion involving a chip.     

Factors associated with racing performance of Thoroughbreds undergoing lag screw repair of condylar fractures of the third metacarpal or metatarsal bone

OBJECTIVE: To evaluate effects of sex, fracture configuration, affected limb, and screw placement on outcome of Thoroughbreds with condylar fractures involving the third metacarpal or metatarsal bone. DESIGN: Cohort study. Animals-56 horses. PROCEDURE: Age, sex, affected limb, fracture configuration, fracture length, fracture fragment width, and distance of the most distal screw from the articular surface were analyzed in logistic regression models. RESULTS: Females were more likely to have displaced fractures and race in fewer races after surgery than males. Sex and fracture configuration were associated with number of postoperative races. Among horses that returned to racing, those with thicker fracture fragments were 11 times as likely as horses with thinner fracture fragments to win a race after surgery. Horses with longer fractures and older horses had fewer postoperative races. Horses in which the most distal screw had been placed further from the joint surface had more races. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that female horses with displaced condylar fractures and male horses with nondisplaced condylar fractures are more likely to be referred for treatment. The effect of sex on outcome for these horses cannot be clearly separated from the effect of fracture configuration. When adjusted for fracture configuration, males were 6 times as likely as females to race after surgery. When adjusted for sex, horses with nondisplaced fractures were 17 times as likely as horses with displaced fractures to race after surgery. Results suggest that the most distal screw should be placed above the epicondylar fossa.     

Risk factors for fatal lateral condylar fracture of the third metacarpus/metatarsus in UK racing

REASONS FOR PERFORMING STUDY: Lateral condylar fractures of the third metacarpus/metatarsus are the most common cause of equine fatality on UK racecourses. Identification of risk factors for such injuries and the subsequent implementation of intervention strategies could significantly reduce the total number of racecourse fatalities. OBJECTIVES: To identify horse-, race- and course-level risk factors for fatal lateral condylar fracture in Thoroughbreds on UK racecourses. METHODS: Case-control study designs were used. Case horses were defined as those that were subjected to euthanasia having sustained an irreparable lateral condylar fracture while racing at any of the 59 UK racecourses. Case races were defined as those in which one or more horses sustained a fatal lateral condylar fracture. Three controls for each case horse were selected at random from the race in which the case was running. Three controls for each case race were selected at random from all races of the same type held in the same year. Ninety-eight cases were included in the study. Conditional logistic regression was used to identify the relationship between a number of independent variables and the likelihood of fracture. RESULTS: Horses doing no gallop work during training and those in their first year of racing were at significantly increased risk of fracture on the racecourse. Case horses were also more likely to have started racing as 3- or 4-year-olds. Fractures were found to be more likely in longer races with a larger number of runners, races in which professional jockeys were not permitted to ride and races in which the going was described as firm or hard. CONCLUSIONS AND POTENTIAL RELEVANCE: Modifications to training schedules, specifically within the first year of racing, may have a large impact on the risk of fatal lateral condylar fracture on the racecourse. Horses should do some gallop work in training and our results suggest that the minimum distance galloped should be between 201 m (1 furlong) and 1609 m (8 furlongs) per week. The association with age at first race requires further investigation for flat and National Hunt racing separately. A reduction in the number of races taking place on very firm going could have an impact on the number of lateral condylar fractures.     

Metatarsal III fractures in the racing greyhound

During a five-year period, six single stress fractures of metatarsal Iii fractures were diagnosed in five greyhounds. All cases occurred while racing and without external trauma. Treatment by external support had previously been unsuccessful in three cases. However, surgical treatment permitted a prompt return to racing in all cases treated. The aetiopathogenesis of these fractures, the relative importance of the functional anatomy of the canine hock and the practice of racing greyhounds around tight curves are discussed.     

Frequency distribution of carpal osteochondral fragmentation in a population of flat racing Thoroughbreds in the UK

Lameness associated with osteochondral fragmentation of the carpus is a common injury in racing horses. Frequency distributions of sites of fragmentation have previously been published in racehorses in the USA, Australia, New Zealand and Japan but not in racing Thoroughbreds in the UK. The objectives of the study were to document sites of osteochondral fragmentation in the carpus of a population of Thoroughbred flat racehorses in the UK and compare these with other Thoroughbred populations globally and other flat racing breeds. This study was a single centre retrospective observational study; case records of flat racing Thoroughbreds with sites of carpal bone fragmentation that underwent arthroscopic surgery at Newmarket Equine Hospital between 2008 and 2013 were reviewed. A total of 291 sites of fragmentation were identified arthroscopically within the carpal joints of 174 horses. This involved 135 (75%) middle carpal (MCj) and 44 (25%) antebrachiocarpal joints (ABCj), which differs from other populations reported. The most common sites of fragmentation were dorsodistal radial carpal bone (DDiCr) (49%), dorsoproximal third carpal bone (DPrC3) (22%), dorsodistal radius (DDiR) (15%), dorsoproximal radial carpal bone (DPrCr) (5%) and dorsoproximal intermediate carpal bone (DPrCi) (4%). The dorsodistal radial carpal bone is also the most common site in American (US) Quarter Horses (QHs) and Thoroughbreds (TBs) and Australian (AUS) TBs, while DPrC3 has a greater prevalence in US Standardbreds (SBs). Thereafter the frequency distribution differs between the reported study groups. Although all horses underwent bilateral radiographic examination, 45% of the total population had unilateral arthroscopic evaluation. This may therefore underestimate the total number of sites of fragmentation reported. In summary the frequency distribution of carpal fragmentation in flat racing Thoroughbreds in the UK appears to differ from other populations of racehorses.     

Determining the endpoint of an outbreak of equine influenza in a large population of racing Thoroughbreds

Outbreaks of equine influenza (EI) cause major disruption to the racing industry, resulting in cessation of racing until affected horses have recovered from the disease. The introduction of EI to a large population of Thoroughbred horses stabled at a Sydney racecourse provided the opportunity to observe clinical signs and monitor the spread of EI in this predominantly na?ve population and to assist in determining an endpoint to infection spread to allow resumption of racing events.