These findings could guide clinicians in the diagnosis of sport related injuries.

Magnetic resonance imaging provides a good representation of cartilage and subchondral bone thickness, supporting its use in the study and clinical diagnosis of osteochondral structure and alteration.

SummaryReasons for performing the study: Lateral condylar (LC) fractures of the third metacarpus (McIII) are a common reason for euthanasia in racehorses, and may be the result of repetitive overloading or cumulative pathological change. Magnetic resonance imaging (MRI) allows monitoring of bone and cartilage to detect pathological and adaptive changes that may be precursors of fracture. Objectives: To describe bone and cartilage MRI features in the distal condyles of McIII of Thoroughbred racehorses, with and without condylar fracture. Hypotheses: 1) A greater degree of bone and cartilage adaptation or pathology will be seen in fractured McIIIs compared with their respective contralateral McIIIs. 2) Contralateral McIIIs will have a greater degree of bone and cartilage adaptation or pathology than McIIIs from control horses that did not sustain a LC fracture. Methods: The McIIIs from 96 horses subjected to euthanasia at racecourses were divided into 3 groups: Group 1: nonfractured bones from horses without LC fracture; Group 2: nonfractured bones from horses with unilateral LC fracture; and Group 3: fractured bones from horses with unilateral LC fracture. The MR images were examined and graded for bone and cartilage changes. Results: Nine percent of Group 1 (n = 9) and 11% of Group 2 bones (n = 5) had incomplete LC fractures. Focal palmar necrosis was most frequently detected in bones from Group 1 (12%) compared with Groups 2 (9%) and 3 (4%). The prevalence of bone and/or cartilage abnormalities tended to increase from Group 1 to Group 2 to Group 3. Conclusions: Magnetic resonance imaging is able to detect cartilage and bone changes that may be associated with LC fracture. There was no significant difference in bone/cartilage changes between bones from Groups 1 and 2, despite increased pathology in Group 2 bones. Potential relevance: Periodic monitoring of bone and/or cartilage changes in distal McIII of Thoroughbred racehorses may help to prevent catastrophic LC fractures.

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This is an author produced version of a paper published in Preventive Veterinary Medicine. This paper has been peer-reviewed but may not include the final publisher proof-corrections or pagination. Orthopaedic, or other, injuries in sports medicine can be quantified using the 'days-lost to 27 training' concept. Both the training regimen and the surface used in training and racing can 28 affect the health of racehorses. Our aim was to associate 'days-lost to training' in elite-level 29show-jumpers to horse characteristics, training and management strategies, and the time spent 30 working on various training and competition surfaces. We designed a longitudinal study of 31 professional riders in four European countries. Data were recorded using training diaries. 32Reasons for days-lost were classified into non-acute and acute orthopaedic, medical, hoof-33 related, and undefined. We produced descriptive statistics of training durations, relative to 34 type of training, surfaces used, and days-lost. We created zero-inflated negative-binomial 35 random-effects models using the overall days-lost as outcome. In the whole dataset, duration 36 variables related to training surfaces were analysed as independent. The Swedish data only 37were also used to test whether duration variables were related to competition surfaces. 38Thirty-one riders with 263 horses provided data on 39,028 days at risk. Of these, 2357 (6.0%) 39were days-lost (55% and 22% of these were due to non-acute and acute orthopaedic injuries, 40 respectively) in 126 horses. 41In the all-country model, controlling for season, a significant variable was country. 42Switzerland and the UK had lower incidence-rate ratios (IR) compared to Sweden (IRs 0.2 43 and 0.03, respectively). Horses with previous orthopaedic problems had almost a doubled IR 44 (1.8) of days-lost due to orthopaedic injury, compared to baseline. If the horse had jumping 45 training more than 1 minute per day at risk the IRs were 6.9-7 (compared to less than this 46 amount of time); this was, however, likely an effect of a small baseline. Variation in training 47 was a protective factor with a dose-response relationship; the category with the highest 48 variation had an IR of 0. horses. Limited training use of sand surface was a risk-factor (IR 2.2; >4≤12 min/day at risk), 54 compared to not training on sand. Training/competing on sand-wood was a protective factor 55 (IRs 0.4-0.5) compared to not using this surface. 56 57