Читать книгу Fractures in the Horse - Группа авторов - Страница 82

Current epidemiological work aimed at minimizing fracture incidence is moving towards prevention by way of accurately identifying horses at significant risk. In order for such predictive models to be useful, it is important that the overall accuracy of prediction is high. At present, the predictive ability of models (Section Predictability and Potential for Effective Screening) is too low for use in a regulatory framework. One of the reasons for this is a lack of detailed information regarding specific aspects of exposure to a wide range of risk factors. A few studies have demonstrated the value of proactively acquiring, otherwise unavailable information. Characteristics of the hoof [66] and shoe [45, 67] and details of veterinary history [19, 62,68–70] have all been shown to be associated with risk.

Multiple measurements of hooves from horses that were subject to euthanasia due to Mc3 condylar fracture or suspensory apparatus failure were compared with hooves from horses whose death was unrelated to the musculoskeletal system [66]. Increasing toe angle, increasing lateral ground surface width and increasing sole area difference (difference between the lateral sole area and medial sole area) were all associated with significantly lower risk of condylar fracture. Increasing sole area difference was also associated with lower risk of suspensory apparatus failure, while increasing toe–heel angle difference was associated with an increased risk of suspensory apparatus failure [66].

Horse shoe characteristics, in particular the use of toe grabs, were strongly associated with the risk of suspensory apparatus failure and Mc3 condylar fracture. Compared with horses shod without toe grabs, low toe grabs increased the odds of each outcome by 6.5 and 7 times, respectively, while the use of regular toe grabs increased the odds by 16 and 17 times, respectively [67]. The odds of suspensory apparatus failure, for horses with rim shoes, was about a third that of horses without [67]. Interestingly, a follow‐up study conducted approximately 10 years later failed to identify the same toe‐grab‐related associations [45]. The authors suggest that this may have been due to the confounding effect of other exercise‐related variables. It is also likely that publicity surrounding the initial work and the subsequent banning of high toe grabs on front shoes is a demonstration of intervention and messaging that has had the desired effect. In other words, 10 years on, the effect of this particular risk factor has somewhat diminished.

The value of being able to include treatment records in predictive models was demonstrated in a study examining the hazard of musculoskeletal injury in the days and weeks following local corticosteroid injection [62]. This compared the incidence in untreated horses or in horses prior to treatment with local corticosteroid injection (1.22 per 100 horse months) with that post treatment. On average, the hazard increased by 4.8 times and only returned to a level that was indistinguishable from that seen in untreated horses or horses prior to treatment after 49 days. Work from the USA was less precise in the estimates of risk, but nevertheless also showed that once a horse has been placed on a ‘vets list’ the risk of fracture for that horse was 80% greater in all future starts, regardless of how long after being placed on the vet list those starts occurred [19]. In certain races in South America, declared use of phenylbutazone is permitted, and horses competing in these races were at approximately 80% greater odds of musculoskeletal injury compared with horses competing in races in which phenylbutazone was not permitted [68, 69]. Similarly, in a case series of almost 1500 horses receiving intrasynovial medication, those horses that had received more than three previous ‘treatments’ were more than twice as likely to sustain a fracture within 56 days, compared with those that had been medicated fewer than four times [70]. Finally, a questionnaire survey of attending veterinarians in California demonstrated that horses that had been subject to euthanasia due to catastrophic musculoskeletal injury were more likely to have been lame in the period three months prior to the date of death [71]. The study also attempted to identify associations with recent medication usage, but largely due to the high proportion of horses (both cases and controls) on medication and the relatively low level of statistical power, no such associations were identified.

In order to better determine the true relationship between veterinary and medication history and the risk of fracture or other injury, it is essential that racing jurisdictions make further attempts to encourage the accurate recording of and willingness to share medical records. Once issues surrounding confidentiality are addressed and this becomes normal practice, the inclusion of such data in future predictive models will undoubtedly improve our ability to better identify horses at increased risk of fracture.