The role of catastrophic injury or sudden death of the horse in race-day jockey falls and injuries in California,

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1 Experimetal ad Basic Research Studies The role of catastrophic ijury or sudde death of the horse i race-day jockey falls ad ijuries i Califoria, P. L. HITCHENS*, A. E. HILL ad S. M. STOVER Departmet of Aimal Eviromet ad Health, Swedish Uiversity ofagricultural Scieces, Uppsala, Swede JD Wheat Veteriary Orthopedic Research Laboratory; School of Veteriary Medicie, Uiversity of Califoria, Davis, USA Califoria Aimal Health ad Food Safety Laboratory System; Uiversity of Califoria, Davis, USA. *Correspodece peta.hitches@slu.se; Received: ; Accepted: Summary Reasos for performig study: If equie coditios with high likelihood of jockey ijury ca be determied ad subsequetly preveted, jockey safety ca be ehaced. Objectives: To idetify racehorse ijuries or coditios with greatest risk for jockey falls ad ijuries. Study desig: Retrospective correlatio of race-day jockey fall ad ijury data with racehorse fatality data. Methods: Thoroughbred (TB) ad Quarter Horse (QH) racehorse cause of death ad jockey fall ad ijury data for Califoria flat races were reviewed for a 6-year period. Race ad jockey race ride populatio data were used to determie jockey fall ad ijury icidece rates relative to cause of racehorse death, ad were assessed usig Poisso regressio. Differeces i proportios were assessed usig Fisher s exact, Pearso s χ, ad Cochra Matel Haeszel tests. Results: 707 racehorses experieced race-related catastrophic ijury or sudde death. 199 jockeys had 601 falls with 35 ijuries. Jockeys were 16 times more likely to fall (95% cofidece iterval ; P<0.001) ad 171 times more likely to be ijured (95% cofidece iterval ; P<0.001) whe they rode a horse that died i a race. We ifer that jockeys were more likely to fall or be ijured whe ridig i QH races tha i TB races because of a higher icidece of horse fatalities i QH races. Jockey falls occurred with 4% of TB ad 36% of QH race-related horse fatalities, ad jockey ijury occurred i 64% of falls. Jockey falls were most commo with TB fetlock ijuries ad QH carpal, metacarpal ad fetlock ijuries; ad with axial, bilateral ad multiple ijuries compared with appedicular, uilateral ad sigular ijuries, respectively. Coclusios: Prevetio of the most commo catastrophic ijuries ad coditios of the racehorse, e.g. fetlock ijuries, may be most effective at decreasig rates of falls ad ijuries to horseracig jockeys durig racig. Keywords: horse; epidemiology; icidece; ijury; jockey; falls Equie Veteriary Joural ISSN DOI: /evj.139 Itroductio Jockeys partake i a highly dagerous occupatio. The most commo cause of jockey falls durig race evets is catastrophic ijury or sudde death of the horse. From 007 to 011, jockeys fell i associatio with 9% of Thoroughbred (TB) ad 44% of Quarter Horse (QH) flat race-related deaths i Califoria [1]. Catastrophic ijury or sudde death of the horse was estimated to cause 0.58 jockey falls per 1000 race rides i TB races ad 1.39 jockey falls per 1000 race rides i QH races. Such falls were more likely to result i jockey ijury tha falls caused by other factors [1]. Musculoskeletal ijuries are the most commo cause of racehorse death [ 5]. The proportio of sudde deaths i TB flat racig horses is estimated at 19% i Australia, 1% i the UK ad 9% i Califoria [,6,7]. Cosequetly, the greatest opportuity to reduce occurrece of ijuries ad fatalities to jockeys is by prevetig catastrophic ijuries ad sudde death i racehorses. The sites ad types of fatal musculoskeletal ijuries ad sudde death for TBs ad QHs i Califoria have bee described [,5,8]. We hypothesised that the site of fatal ijury or a sudde death evet icurred by racehorses durig races affects the likelihood of ijury to the jockey. Our objective was to compare jockey fall ad ijury rates amog causes of racehorse death for TB ad QH flat races. The fidigs will assist i the prioritisatio of strategies that prevet racehorse ijuries ad thus lead to ehaced jockey welfare. Materials ad methods Data sources Jockey falls from horses associated with races i Califoria from 1 Jauary 007 to 31 December 01 were collated from jockey accidet reports submitted by racetrack stewards to the Califoria Horse Racig Board for all o-track accidets ivolvig jockeys. Each accidet report was scaed electroically, ad a keyword search was coducted for ay report of a rider fallig or beig dislodged from a horse. Jockey outcome was categorised as ijured if the jockey: 1) had a substative ijury that precluded the jockey from ridig; ) was declared ufit to ride; or 3) was trasported to a hospital followig a fall. The site of catastrophic ijury or cause of sudde death (icludig other fatal collapse) was obtaied for deceased racehorses from post mortem ecropsy reports. All horses that died or were subjected to euthaasia o a racetrack uder the jurisdictio of the Califoria Horse Racig Board were ecropsied at a Califoria Aimal Health ad Food Safety laboratory. Post mortem records for all TB ad QH racehorses submitted to Califoria Aimal Health ad Food Safety from 1 Jauary 007 to 31 December 01, ad that died as a result of a race-day icidet were examied; oexercise or traiig related icidets were excluded. Racehorses that died as a result of a ijury sustaied idirectly by a race-day icidet were excluded from the aalysis of jockey falls ( = 11; 5 clipped heels ad fell, hampered by aother falle horse, horse behaviour [flipped over i startig gate, ra through ruig rail durig pre-race warm up], oe iterferece by aother horse, oe horse shifted groud abruptly). For these racehorses, experiecig a catastrophic ijury or sudde death was ot oted as the reaso for the jockey fallig. The site of the primary catastrophic ijury or the coditio that caused death was categorised for comparisos by oe author (S.M.S.) as: frot limb, hidlimb or axial (spie ad pelvis); left or right limb; uilateral or bilateral for ijuries to the same boe (e.g. left ad right forelimb metacarpal boe fractures); sigle or multiple boes affected (e.g. metacarpal ad tibial boes); ad soft tissue oly (e.g. suspesory ligamet rupture) or boe ijury with or without soft tissue ijury (e.g. proximal sesamoid boe fracture with suspesory ligamet brach rupture). Deomiator data, icludig the umber of horse races, race days ad jockey race rides were obtaied for TB [9] ad QH [10] races for Califoria race meets from 1 Jauary 007 to 31 December Equie Veteriary Joural 48 (016) EVJ Ltd

2 TABLE 1: Cotigecy tables comparig jockeys that rode a horse that died from a musculoskeletal ijury or sudde death (icludig other fatal collapse) i a race with jockeys that did ot Jockey ijuries Jockey falls Horses starts/jockey rides No Yes Total No Yes Total All Death (17.4%) (7.0%) 707 Nodeath 63,146 0 (0.1%) 63,348 6, (0.%) 63,348 Total 63, (0.1%) 64,055 63, (0.%) 64,055 TB Death (15.6%) (4.1%) 57 Nodeath 10, (0.1%) 10,984 10, (0.%) 10,984 Total 11,79 3 (0.1%) 11,511 11, (0.%) 11,511 QH Death (.8%) (35.6%) 180 Nodeath 5,31 5 (0.1%) 5,364 5,7 9 (0.%) 5,364 Total 5, (0.%) 5,544 5, (0. 3%) 5,544 Data aalysis Jockey accidet data were merged with equie post mortem data by oe-to-oe matchig o horse ame, icidet date ad racetrack. Icidece rates were expressed as umber of falls or ijuries per 1000 race rides. Icidece rate ratios (IRR), with 95% cofidece itervals (CI), were estimated usig Poisso regressio. Descriptive statistics of catastrophic ijury ad sudde death of the horse ad of related jockey falls ad ijuries are preseted. Supplemetary Item 1, a flowchart of a jockey fall associated with horse fatality, idicates how horse ad jockey falls were classified. The differece i proportios of racehorse catastrophic ijuries or sudde death resultig i a jockey fall ad/or ijury betwee breed of racehorse, were assessed by creatig cotigecy tables ad coductig Fisher s exact test, Pearso s χ test for idepedece, ad the Cochra Matel Haeszel (CMH) test for compariso of groups by racehorse breed. Multiple ad bilateral ijuries were excluded from these aalyses of proportios. All statistical aalyses were coducted usig Stata, versio 1.0 (StataCorp, College Statio, Texas, USA). Results Jockeys were 16 times more likely to fall (95% CI ; P<0.001) ad 171 times more likely to be ijured (95% CI ; P<0.001) whe the jockeys rode a horse that died from a musculoskeletal ijury or sudde death i a race. Over the study period, 199 jockeys had 601 jockey falls ad 35 associated jockey ijuries from 11,511 TB race rides ad 5,544 QH race rides. A total of 707 racehorses experieced race-related catastrophic ijury or sudde death. Of the jockey falls, 3% were caused by catastrophic ijury or sudde death of the horse, with jockeys ijured i 64% of falls, for approximately 1 ijurious jockey falls per year o average. Jockey falls occurred i associatio with 4% of TB ad 36% of QH race-related horse fatalities, ad were ijured i 16% of TB ad 3% of QH icidets. Jockey ijuries resulted from 64% of falls from associated TB ad QH fatalities, but this accouted for oly 38% of race-related jockey ijuries, 0% of race-related jockey falls, ad 0.05% of total starts i TB ad QH races (Table 1). There were jockey fatalities: oe was caused by catastrophic ijury to the carpus of a -year-old QH; a horse clippig heels caused the other, which was ot icluded i aalysis because the horse beig ridde did ot sustai a catastrophic ijury. Icidece rates For the 6-year study period, QH races were associated with a higher icidece of horse fatalities, ad a higher icidece of jockey falls ad ijuries (sustaied whe ridig racehorses that experieced a catastrophic ijury or sudde death), tha TB races (Table ). Jockey falls that resulted from catastrophic ijury or sudde death of the horse occurred every 1665 starts for TB races ad 81 starts for QH races. The aual jockey fall icidece rates that resulted from catastrophic ijury or sudde death of a horse for TB ad QH racig had high variability but did ot chage (P = 0.8 ad P = 0.6, respectively) over the study period (Fig 1). Jockey falls related to catastrophic ijury or death of the horse were more likely to result i jockey ijury (65% ijured) compared with falls caused by other factors (47% ijured) i TB races (P<0.001), but ot i QH races (64% ijured for falls related to catastrophic ijury or death of the horse vs. 57% ijured for falls caused by other factors; P = 0.3) (Tables 3 ad 4). Catastrophic ijury vs. sudde death of horse Jockey falls ad ijuries caused by horse catastrophic musculoskeletal ijuries were more frequet tha those caused by sudde death, ad this did ot differ betwee racehorse breeds (CMH jockey falls P>0.9; jockey ijuries P = 0.5). Jockey falls were more likely to result i jockey ijury for sudde deaths tha catastrophic musculoskeletal ijuries i TB races (Fisher s exact P = 0.09) although ot i QH races (Fisher s exact P = 1.000), but sudde deaths oly accouted for jockey falls i QH races (Supplemetary Item ). I TB races, jockeys sustaied a ijury followig 15% of all racehorse catastrophic musculoskeletal ijuries ad % of all sudde deaths (Fisher s exact P = 0.4). I QH races, jockeys sustaied TABLE : Icidece rate ratio (IRR) ad 95% cofidece itervals (CI) of jockey falls ad ijuries associated with catastrophic musculoskeletal ijury or sudde death (icludig other fatal collapse) of the horse, betwee racehorse breeds Jockey ijury Jockey fall Horse fatality Breed IRR (95% CI) IRR (95% CI) IRR (95% CI) Thoroughbred 8 Ref 17 Ref 57 Ref Quarter Horse (1.38,.93)* (1.50,.74)* (1.16, 1.63)* *P< Equie Veteriary Joural 48 (016) EVJ Ltd 51

3 5 4 Icidece of jockey falls per 1000 race rides 3 1 Fig 1: Icidece of jockey falls by catastrophic ijury or sudde death of the horse (death) compared with other factors, by racehorse breed TB other TB death QH other QH death a ijury followig 3% of all racehorse catastrophic musculoskeletal ijuries ad 17% of all sudde deaths (Fisher s exact P = 1.000; Supplemetary Item 3). Site of horse catastrophic ijury Excludig horses with multiple catastrophic ijuries, the differece betwee the proportios of jockey falls amog catastrophic ijury sites (frot, hid or axial) by breed differed sigificatly (CMH P = 0.004). Catastrophic forelimb ijury caused the most jockey falls ad ijuries (Figs ad 3). Excludig multiple ijuries, a high proportio of jockeys who fell experieced a fall whe ridig a horse that sustaied a axial catastrophic ijury (TB 1%, QH 68%), followed by forelimb (TB 4%, QH 31%) ad hidlimb (TB 11%, QH 11%) racehorse ijuries. Axial catastrophic ijuries were more commoly sustaied with multiple catastrophic ijuries compared with sigular ijuries for TBs (Fisher s exact P<0.001) resultig i 33% of jockey falls, but ot for QHs (Fisher s exact P = 0.1). Excludig multiple ijuries, i TB races, jockeys sustaied a ijury followig 17% of racehorse catastrophic musculoskeletal ijuries to the forelimb, 3% of ijuries to the hidlimb, ad 6% of axial ijuries (Fisher s exact P = 0.0). I QH races, jockeys sustaied a ijury followig 19% of racehorse catastrophic musculoskeletal ijuries to the forelimb, 0% of ijuries to the hidlimb, ad 53% of axial ijuries (Fisher s exact P = 0.001; Supplemetary Item 4). The proportio of jockey falls ad ijuries did ot differ betwee sides (left vs. right) of catastrophic forelimb ijury by breed (Supplemetary Item 5; CMH P = 0. ad P = 0.4, respectively); or for jockey falls for hidlimb catastrophic ijury by breed (CMH P = 0.6). Few jockey ijuries resulted from catastrophic horse ijury to the left hidlimb (QH = 1;TB = ),ad oe resulted from catastrophic ijury to the right hidlimb. Bilateral ijuries that resulted i a jockey fall predomiatly icluded ijuries to the carpus, metacarpus or fetlock for TBs ad QHs. Jockeys more commoly experieced a fall whe ridig a horse that sustaied a bilateral catastrophic ijury (73% i TBs, 86% i QHs) tha a uilateral ijury (3% i TBs, 6% i QHs; Fisher s exact TBs P = 0.001, QHs P<0.001). I TB races, jockeys sustaied a ijury followig 15% of racehorse catastrophic uilateral musculoskeletal ijuries ad 55% of bilateral ijuries (Fisher s exact P = 0.003). I QH races, jockeys sustaied a ijury followig 16% of racehorse catastrophic uilateral musculoskeletal ijuries ad 50% of bilateral ijuries (Fisher s exact P = 0.006, Supplemetary Item 6). A small percetage of horse fatalities (% of TB fatalities; 3% of QH fatalities) icluded multiple catastrophic musculoskeletal ijuries (see Supplemetary Item 7 for detailed iformatio). A high proportio of those horse fatalities resulted i a jockey fall (64% of TB fatalities, Fisher s exact P = 0.006; 100% of QH fatalities, Fisher s exact P = 0.005) ad ijury (7% of TB fatalities, Fisher s exact P = 0.; 80% of QH fatalities, Fisher s exact P = 0.010) compared with horse fatalities as a result of sigular ijuries (Supplemetary Item 8). Proportios of jockey falls ad ijuries from multiple catastrophic ijuries were ot differet betwee racehorse breeds (CMH P = 0. ad P = 0.1 respectively). Not icludig multiple ijuries, 13 racehorses (TB =8;QH=5)had race-related soft-tissue ijuries. The proportio of soft-tissue ijuries compared with boe ijuries that resulted i a jockey fall or ijury did ot differ by racehorse breed (Supplemetary Item 9; CMH P = ad P = 0.875, respectively). Discussio The roles of catastrophic ijury or sudde death of the horse i jockey falls ad ijuries that occurred at TB ad QH race meetigs i Califoria for a 6-year period were studied. Jockeys were 16 times more likely to fall ad 171 times more likely to be ijured whe they rode a horse that died i a race. We ifer that jockeys were more likely to fall or be ijured whe ridig i QH races tha i TB races because of a higher icidece of horse fatalities. Jockey falls were most commo with TB fetlock ijuries ad QH carpal, metacarpal ad fetlock ijuries; ad with axial, bilateral ad multiple ijuries compared with appedicular, uilateral ad sigular ijuries, respectively. Catastrophic racehorse ijuries that resulted i the highest frequecy of jockey falls ad ijuries were uilateral musculoskeletal ijuries to the forelimb, largely because of the high prevalece of these ijuries amog all catastrophic musculoskeletal ijuries. I TB races, jockey falls related to catastrophic ijury or death of the horse were more likely to result i jockey ijury compared with falls that were caused by other factors (e.g. horse behaviour). This was ot see i QH races, ad this may be because QHs race over shorter distaces [11] ad at greater speeds [1] tha TBs, ad that falls uder these circumstaces, regardless of cause, have a greater likelihood of resultig i ijury to the jockey. With a additioal year s data, this result is i agreemet with the group s previous study [1]. Jockey falls that were a result of horse catastrophic musculoskeletal ijury to the forelimb, particularly to the fetlock i TBs ad the carpus, metacarpus ad fetlock i QHs, were most commo. However, jockeys 5 Equie Veteriary Joural 48 (016) EVJ Ltd

4 TABLE 3: Jockey falls ad ijuries caused by catastrophic ijury or sudde death (icludig other fatal collapse) of a TB racehorse, from 007 to 01 for racig i Califoria Jockey ijuries Jockey falls Horse fatalities Site of horse CMI or coditio by site* by site** Jockey ijuries/fall (%) % of total horse fatalities*** Forelimb 73 17% 110 6% 66% 45 76% Scapula 3 43% 3 43% 100% 7 1% Humerus 3 43% 5 71% 60% 7 1% Radius/ula 40% 3 60% 67% 5 1% Carpus 5 8% 7 1% 71% 59 11% Metacarpus 1 4% 7 54% 78% 50 9% Fetlock 39 13% 65 % 60% 90 5% Paster 0 0% 0 0% 7 1% Hidlimb 1 % 6 15% 17% 41 7% Femur/tibia 0 0% 50% 0% 4 1% Metatarsus 1 17% 33% 50% 6 1% Fetlock 0 0% 1 5% 0% 19 3% Paster 0 0% 0 0% 8 1% Tarsus 0 0% 1 5% 0% 4 1% Bilateral# 6 55% 8 73% 75% 11## % Carpus 100% 100% 100% 0% Metacarpus 67% 3 100% 67% 3 1% Fetlock 40% 3 60% 67% 5 1% Axial 5% 13 33% 15% 39 7% Skull 0 0% 0 0% 4 1% Cervical spie 0% 5 50% 40% 10 % Thoracic spie 0 0% 0 0% 1 0% Lumbar spie 0 0% 4 67% 0% 6 1% Sacral vertebrae 0 0% 100% 0% 0% Pelvis 0 0% 13% 0% 16 3% Soft tissue 3 33% 3 33% 100% 9 % Sudde death 6 % 6 % 100% 7 5% Multiple MS# 3 7% 7 64% 43% 11 % Total horse fatalities# 8 16% 17 4% 65% % Total of colum 94 17% 153 7% 61% % Jockey falls ad ijuries caused by other factors (ot related to CMI/SD) 150 /a 318 /a 47% /a /a #Bilateral ad multiple ijuries are couted i other relevat categories, but total horse fatalities does ot iclude duplicates; ##Oe racehorse had bilateral tedoitis; = umber; MS = musculoskeletal; CMI/SD = catastrophic musculoskeletal ijury or sudde death (icludig other fatal collapse); *deotes umber of jockey ijuries/umber of horse CMI or SD at each site as a percetage; **deotes umber of jockey falls/umber of horse CMI or SD at each site as a percetage; ***deotes umber of horse CMI or SD at each site/total umber of horse fatalities. were more likely to experiece a fall whe ridig a horse that sustaied a axial catastrophic ijury. Few jockey falls or ijuries resulted from catastrophic hidlimb ijuries to the horse. Catastrophic ijuries to horses that resulted i the greatest proportio of jockey ijuries i TB races were those to the scapula ad humerus (43%), metacarpus (4%), radius or ula (40%), ad bilateral ijuries to the carpus (100%), metacarpus (67%) ad fetlock (40%). I QH races, catastrophic horse ijuries that resulted i the greatest proportio of jockey ijuries were those to the metacarpus (77%), vertebrae (60%; 1 jockey ijuries from 0 racehorse catastrophic vertebral ijuries), radius or ula (50%), tarsus (40%) ad scapula (9%). The distributio of catastrophic musculoskeletal ijuries was similar to that observed i other studies [,5,13]. However, the rate of race-related horse fatality was higher tha reported previously [5,11,14], although those studies icluded data from the precedig decade. We did ot have data o jockey falls or ijuries from the previous decade, but it could be hypothesised that a icrease i horse fatalities could lead to a icrease i associated jockey falls ad ijuries. This icrease has bee attributed to a icrease i fatal ijuries of structures that support the fetlock regio [8]. Recogisig that pre-existig pathological coditios commoly precede catastrophic ijury i the horse [8], opportuities to detect these coditios may i tur result i the reductio of the icidece of jockey falls ad ijuries. Jockey falls ad ijuries resultig from horse catastrophic musculoskeletal ijuries were more frequet tha those as a result of sudde death, but there was a higher likelihood of ijurious jockey falls occurrig i associatio with sudde deaths tha catastrophic musculoskeletal ijuries i TB races. Horse fatalities that icluded sudde death, as well as bilateral, multiple or axial catastrophic musculoskeletal ijuries, more frequetly resulted i a jockey fall or ijury. These horse fatalities may typically ivolve the horse collapsig to the track. The impact velocities of falls by jockeys have bee foud to rage from about 30 to 50 km/h, from heights of up to about 3.5 m [15], ad we suppose that alog with these impact velocities, the additio of the jockey fallig with the horse, ad a chace of beig crushed or struck by that horse, or others followig, puts the jockey at great risk of ijury. Future studies icorporatig video aalysis may help to decipher such ijury mechaisms. Iformatio o jockey falls ad ijuries that occurred durig traiig or workouts was ot available, but because of the high icidece of catastrophic ijury to horses durig traiig [,5,8,14,16], traiig ijuries Equie Veteriary Joural 48 (016) EVJ Ltd 53

5 TABLE 4: Jockey falls ad ijuries caused by catastrophic ijury or sudde death (icludig other fatal collapse) of a QH racehorse, from 007 to 01 for racig i Califoria Jockey ijuries Jockey falls Horse fatalities Site of horse CMI or coditio by site* by site** Jockey ijuries/fall (%) % of total horse fatalities*** Forelimb 9 0% 47 33% 6% 14 70% Scapula 9% 5 71% 40% 7 3% Radius/ula 50% 3 75% 67% 4 % Carpus 10 14% 15 % 67% 69 34% Metacarpus 10 77% 1 9% 83% 13 6% Fetlock 5 11% 11 4% 45% 45 % Paster 0 0% 1 5% 0% 4 % Hidlimb % 3 33% 67% 9 4% Femur/tibia 0 0% 0 0% 1 <1% Fetlock 0 0% 0 0% 1% Tarsus 40% 40% 100% 5 % Sacroiliac joit 0 0% 1 100% 0% 1 <1% Bilateral# 7 50% 1 86% 58% 14 7% Carpus 3 38% 6 75% 50% 8 4% Metacarpus 3 75% 4 100% 75% 4 % Fetlock 1 100% 1 100% 100% 1 <1% Sacroiliac joit/sacral tubers 0 0% 1 100% 1 <1% Axial 13 59% 16 73% 81% 11% Cervical spie 67% 3 100% 67% 3 1% Lumbar spie 8 53% 10 67% 80% 15 7% Sacral vertebrae 100% 100% 100% 1% Pelvis 1 50% 1 50% 1% Soft tissue 40% 40% 100% 5 % Sudde death 1 17% 33% 50% 6 3% Multiple MS# 4 80% 5 100% 80% 5 % Total horse fatalities# 41 3% 64 36% 64% % Total of colum 58 9% 87 43% 67% % Jockey falls ad ijuries caused by other factors (ot related to CMI/SD) 5 /a 9 /a 57% /a /a #Bilateral ad multiple ijuries are couted i other relevat categories, but total horse fatalities does ot iclude duplicates; = umber; MS = musculoskeletal; CMI/SD = catastrophic musculoskeletal ijury or sudde death (icludig other fatal collapse); *deotes umber of jockey ijuries/umber of horse CMI or SD at each site as a percetage; **deotes umber of jockey falls/umber of horse CMI or SD at each site as a percetage; ***deotes umber of horse CMI or SD at each site/total umber of horse fatalities. are likely to cotribute substatially to the icidece of jockey ad exercise rider ijuries. Although there were few cases, all jockey falls associated with a race that were a result of soft-tissue racehorse ijuries resulted i a jockey ijury. It is possible that some ijuries were misclassified due to the retrospective review of free text post mortem reports, which varied a) Thoroughbred i structure ad detail because they were produced by multiple pathologists. The data o jockey ijuries were ot provided by a medical professioal, ad thus may be a uderestimatio of ijuries that did ot preclude the jockey from cotiuig to ride. A Jockey Ijury Database is beig piloted i Keeelad, Ketucky ad aims to implemet a stadardised ijury reportig system for the racig idustry atio- b) Quarter Horse 0 Number of racehorses Number of racehorses 0 40 Forelimb Hidlimb Bilateral Axial Soft tissue Sudde death Multiple MS Forelimb Hidlimb Bilateral Axial Soft tissue Sudde death Multiple MS Fig : Jockey falls ad ijuries by racehorse ijury site, stratified by racehorse breed. MS = musculoskeletal. Jockey uijured Jockey ijured Jockey uijured Jockey ijured 54 Equie Veteriary Joural 48 (016) EVJ Ltd

6 a) Ackowledgemets The authors thak the Califoria Horse Racig Board for fudig ad provisio of jockey accidet reports, Jeie Hawkis for collatio of reports, ad the Califoria Aimal Health ad Food Safety Laboratory System for racehorse catastrophic ijury data. 3 Authorship P.L. Hitches was resposible for obtaiig approvals, desig ad coduct of the study, data collectio, data maagemet ad cleaig, ad compiled the iitial draft of the mauscript. P.L. Hitches, A.E. Hill ad S.M. Stover udertook the aalysis ad iterpretatio of the data, completed revisios, ad approved the fial mauscript. P.L. Hitches had full access to all the data i the study ad takes resposibility for the itegrity of the data ad the accuracy of the data aalysis Refereces 39 b) Fig 3: Number of jockey ijuries by racehorse ijury site, stratified by racehorse breed: a) Thoroughbred, b) Quarter Horse. wide [17]. Likig iformatio from this database to records of fatal ad ofatal ijuries experieced by racehorses will facilitate prioritisatio of research that prevets jockey ijuries through prevetio of racehorse ijuries. I summary, this study is the first to ivestigate the role of catastrophic musculoskeletal ijury ad sudde death of racehorses o the characteristics ad icidece rates of jockey falls ad ijuries durig TB ad QH flat races. We foud that catastrophic musculoskeletal ijuries to the horse are sigificatly associated with jockey falls ad ijuries. Although there were some skeletal sites (e.g. axial ijuries) or circumstaces (e.g. bilateral ijuries) where catastrophic ijury had a higher proportio of jockey falls ad ijuries, the prevaleces of jockey falls ad ijuries are largely related to skeletal sites with the largest prevalece of catastrophic ijuries, the fetlock, carpus ad metacarpus. Authors declaratio of iterests No competig iterests have bee declared. Ethical aimal research The Uiversity of Califoria, Davis, Istitutioal Review Board (IRB) waived the eed for review (Referece: ). Source of fudig The Califoria Horse Racig Board provided fudig for this research. Equie Veteriary Joural 48 (016) EVJ Ltd 1. Hitches, P.L., Hill, A.E. ad Stover, S.M. (013) Jockey falls, ijuries, ad fatalities associated with Thoroughbred ad Quarter Horse racig i Califoria, Orthop. J. Sports Med. doi: / Johso, B.J., Stover, S.M., Daft, B.M., Kider, H., Read, D.H., Barr, B.C., Aderso, M., Moore, J., Woods, L., Stoltz, J. ad Blachard, P. (1994) Causes of death i racehorses over a years period. Equie Vet. J. 6, Heradez, J., Hawkis, D.L. ad Scollay, M.C. (001) Race-start characteristics ad risk of catastrophic musculoskeletal ijury i Thoroughbred racehorses. J. Am. Vet. Med. Ass. 18, Peloso, J.G., Mudy, G.D. ad Cohe, N.D. (1994) Prevalece of ad factors associated with musculoskeletal racig ijuries of Thoroughbreds. J. Am. Vet. Med. Ass. 04, Sarrafia, T.L., Case, J.T., Kide, H., Daft, B.M., Read, D.H., Moore, J.D., Uzal, F.A. ad Stover, S.M. (01) Fatal musculoskeletal ijuries of Quarter Horse racehorses: 314 cases ( ). J. Am. Vet. Med. Ass. 41, Lyle, C.H., Uzal, F.A., McGorum, B.C., Aida, H., Blissitt, K.J., Case, J.T., Charles, J.T., Garder, I., Horadagoda, N., Kusao, K., Lam, K., Pack, J.D., Parki, T.D., Slocombe, R.F., Stewart, B.D. ad Bode, L.A. (011) Sudde death i racig Thoroughbred horses: a iteratioal multicetre study of post mortem fidigs. Equie Vet. J. 43, Bode, L.A., Aderso, G.A., Charles, J.A., Morga, K.L., Morto, J.M., Parki, T.D.H., Slocombe, R.F. ad Clarke, A.F. (006) Risk of fatality ad causes of death of Thoroughbred horses associated with racig i Victoria, Australia: Equie Vet. J. 38, Stover, S.M. ad Murray, A. (008) The Califoria Postmortem Program: leadig the way. Vet. Cli. N. Am.: Equie Pract. 4, The Jockey Club (01) 01 Califoria Fact Book: a statistical guide to the Thoroughbred idustry i Califoria, The Jockey Club, Lexigto Ketucky. p America Quarter Horse Associatio (01) Q-Racig Joural: statistics supplemet. March 01, Vallace, S.A., Case, J.T., Etwistle, R.C., Kide, H., Barr, B.C., Moore, J., Aderso, M.L., Arthur, R.M. ad Stover, S.M. (01) Characteristics of Thoroughbred ad Quarter Horse racehorses that sustaied a complete scapular fracture. Equie Vet. J. 44, Nielse, B.D., Turer, K.K., Vetura, B.A., Woodward, A.D. ad O Coor, C.I. (006) Racig speeds of Quarter Horses, Thoroughbreds ad Arabias. Equie Vet. J. 38, Atheill, L.A., Stover, S.M., Garder, I.A., Hill, A.E., Lee, C.M., Aderso, M.L., Barr, B.C., Read, D.H., Johso, B.J., Woods, L.W., Daft, B.M., Kide, H., Moore, J.D., Farma, C.A., Odai, J.S., Pesaveto, P.A., Uzal, F.A., Case, J.T. ad Ardas, A.A. (006) Associatio betwee fidigs o palmarodorsal radiographic images ad detectio of a fracture i the proximal sesamoid boes of forelimbs obtaied from cadavers of racig Thoroughbreds. Am. J. Vet. Res. 67, Estberg, L., Stover, S.M., Garder, I.A., Johso, B.J., Case, J.T., Ardas, A., Read, D.H., Aderso, M.L., Barr, B.C., Daft, B.M., Kide, H., Moore, J., Stoltz, J. ad Woods, L. (1996) Fatal musculoskeletal ijuries icurred durig racig ad traiig i Thoroughbreds. J. Am. Vet. Med. Ass. 08,

7 15. Gibso, T., Thai, K., Saxo, J. ad Foote, C. (007) The effectiveess of jockey safety equipmet i falls [Abstract]. J. Biomech. 40, S133-S Stover, S.M. (003) The epidemiology of Thoroughbred racehorse ijuries. Cli. Tech. Equie Pract., The Jockey s Guild (01) Media release: Jockeys Guild aouces lauch of Jockey Ijury Database; aim is to track treds, protect riders, Nicholasville, Ketucky. Supportig iformatio Additioal Supportig Iformatio may be foud i the olie versio of this article at the publisher s website: Supplemetary Item 1: Flow chart demostratig how a jockey fall or ijury might occur. Supplemetary Item : Proportios of ijurious jockey falls caused by horse catastrophic musculoskeletal ijuries compared to those caused by sudde death, stratified by racehorse breed. Supplemetary Item 3: Jockey falls ad ijuries caused by horse catastrophic musculoskeletal ijuries compared to those caused by sudde death, stratified by racehorse breed. Supplemetary Item 4: Jockey falls ad ijuries by site of horse catastrophic musculoskeletal ijury, stratified by racehorse breed. Supplemetary Item 5: Jockey falls ad ijuries by side (left vs right) of horse catastrophic musculoskeletal ijury i the forelimb, stratified by racehorse breed. Supplemetary Item 6: Jockey falls ad ijuries by uilateral ad bilateral horse catastrophic musculoskeletal ijury i the forelimb, stratified by racehorse breed. Supplemetary Item 7: Details of multiple musculoskeletal ijuries, sudde death or other fatal collapse, ad soft tissue ijuries. Supplemetary Item 8: Jockey falls ad ijuries by sigular ad multiple horse catastrophic musculoskeletal ijuries, stratified by racehorse breed. Supplemetary Item 9: Jockey falls ad ijuries by horse catastrophic musculoskeletal ijuries to the soft tissue ad boe, stratified by racehorse breed. The Racehorse: A Veteriary Maual Author: P.H. Ramza Publisher: CRC Press, August 014 Hardback, 380 pages Writte by oe of the UK s leadig equie veteriary practitioers, this textbook is dedicated wholly to the veteriary maagemet of the racehorse. The Racehorse: A Veteriary Maual brigs together all the major orthopaedic ad o-orthopaedic coditios likely to be ecoutered i racehorse practice ad cocisely details state-of-the-art best practice for diagosis ad maagemet. The book spas the full rage of fields relevat to the cliicia, icludig topics as diverse as rehabilitatio, respiratory medicie, exercise physiology, prepurchase ad herd health. Well-illustrated ad comprehesive, it succeeds i beig both practical ad firmly evidece based, makig it a ivaluable resource for cliicias worldwide as well as a useful referece work for may o-veteriarias i the racig idustry. Provides a comprehesive referece text for cliicias ad idustry professioals workig with racehorses Takes a practical approach to diagosis ad maagemet of racehorse ijuries ad diseases Cocisely summarises curret approaches to treatmet of orthopaedic ad o-orthopaedic coditios, based o reviewed equie ad huma sports medicie literature as well as the collective experiece of oe of the world s leadig equie practices Supplies iformatio relevat to all the major racig jurisdictios Provides ivaluable advice o rehabilitatio periods ad progosis for orthopaedic ijuries EVJ price: plus p&p BEVA member price: plus p&p EVJ Bookshop, Mulberry House, 31 Market Street, Fordham, Ely, Cambs. CB7 5LQ, UK Tel: Fax: bookshop@evj.co.uk 56 Equie Veteriary Joural 48 (016) EVJ Ltd