in the 1980s [72]. Determination of increased metabolic activity in bone allowed identification of suspected fractures in areas of limited imaging capability or in some cases in advance of identifiable (usually radiographic) morphologic changes [73].
After nearly a century of interpreting radiographic information on photographic film, digital imaging became the norm and with it substantially more information on bone structure and fracture identification. However, radiographs are two‐dimensional assessments of a three‐dimensional object with superimposition of other structures. They are therefore limited in assessing the geometry of fractures that are not simple and uniplanar. Introduction of computed tomography (CT) in the last decade provided three‐dimensional radiographic information and has been a great step forward resulting in the re‐classification of many fractures from incomplete to complete, uniplanar to spiral and simple to comminuted. Confident identification of fractures has not only directed optimal management but has also permitted minimally invasive repair.
Ex vivo (post‐mortem) use of CT and magnetic resonance imaging (MRI) to evaluate equine fractures was reported in 1995 [74]. Both produce sectional multiplanar images, but these are based on different information sources. CT relies on tissue attenuation of X‐rays; MRI principally maps the presence of hydrogen atoms (particularly in water and fat), and structural information of the skeleton is inferred from this [75]. CT identification of a two‐dimensional radiographically occult fracture was reported in 1999 [76], and in 2001 Tucker and Sande [77] identified the potential for CT to better delineate fracture orientation and assist in surgical planning in horses. Subsequent development and adoption of mobile in‐theatre units made this a reality, and CT is currently considered the gold standard in assessing and directing repair of equine fractures. In vivo diagnostic use of MRI for the evaluation of equine fractures started to appear in 2010 [78] with subsequent contributions to understanding pathogenesis [79], surgical planning [80] and risk assessment [81].
Inherent surgical limitations are now recognized in veterinary medicine [82]. Those who regularly deal with equine fracture repair understand the importance of team work, attention to detail, communication and planning. The ideas crystallized in the publications of Atul Gawande [83–85] are as relevant to equine surgeons as their human counterparts. An international World Health Organisation (WHO) study demonstrated that adoption of a surgical checklist reduced human post‐operative morbidity and mortality by 36% and 48%, respectively [86]. Multiple subsequent studies have upheld these findings in man, and similar results have been reported in veterinary anaesthesia [87] and small animal surgery [88, 89].
The Future
Ethereal debate centred on the question of ‘what is a fracture?’ is anticipated. The dictionary definition of ‘being broken, of a crack, division or split’ [90] is clear, but at what level? Division of a bone into two or more pieces is indisputable and all would agree that incomplete fissures in cortical or subchondral compacta are fractures. But should disrupted trabeculae in spongiosa be similarly classified? Do some enostoses represent fractures in trabecular bone [91]? Are the recently adopted terms of ‘bone failure’, ‘bone bruising’ and ‘fatigue failure’ manifestations of fractures at a microscopic level?
If the veterinary profession wishes to retain its role as guardians of animal welfare, then future endeavours will need to include measures targeting prevention or reduction of fracture incidence in horse sports, particularly racing. Elements of society have and will continue to question whether use of horses for competitive sport is ethical and, rather more directly, whether ‘horseracing is too dangerous?’ [92]. In some countries, animals are also gradually moving from the legal status of chattel to sentient beings: with that will come rights and this may herald a change in society's attitudes. The veterinary profession is best positioned to provide objective guidance. Suggestions that with the right insight nearly every catastrophic fracture in flat racehorses could be foretold [93] are not justifiable. However, the prevention of some work/stress‐related fractures through conditioning and training methods, surface design and maintenance [94] and potentially from genetic studies [95] appears feasible goals. Robust epidemiological studies should identify risk factors, enable change to be rational and, if both are correct, reduction in work‐related (stress) fractures is a reasonable expectation. Unfortunately, epidemiologic evidence thus far is inconsistent [96]. Previously heralded mineral‐based dietary influences appear unlikely to contribute [97]. Screening of horses in training or monitoring at‐risk individuals by biomarkers as yet appears to lack sensitivity and specificity [98]. Assessment by diagnostic imaging is an attractive concept but remains unproven [95,99–104]. Longitudinal studies, of which there are few in man [105], are a laudable goal [95] but unlikely to be practical in equine athletes.
Notwithstanding the above, monotonic fractures that result from trauma will continue to present and challenge veterinarians. The potential for survival, humane preservation of life and return to useful function continues to progress proximally in the horse's limb. Development of CT equipment that will allow three‐dimensional evaluation of the proximal appendicular and axial skeleton appears close to the horizon. Variable angle LCPs (VA‐LCP) are now in production for man and should soon join the veterinary surgeons’ armamentarium [42]. Refinements such as the addition of hard carbon film to improve drill efficiency and reduce bone temperature may become the norm [106]. Further development of biodegradable plates and screws is anticipated together with drug, osteoconductive and osteoinductive coatings to implants [42, 107, 108]. Customized implants made using 3D printing technology are also an enticing prospect but access to adequate technological knowledge and appropriate materials is unlikely to be widespread in equine surgery. Computer‐assisted surgery in horses is in its infancy [109, 110] but will not be a substitute for anatomic knowledge or surgical skill. There is little current evidence to support clinical application of cellular, growth factor or cell signalling molecules in improving the rate or quality of fracture healing [42]. However, in common with other regenerative disciplines, targeted nuclear manipulation appears rational and holds promise.
It has been stated that orthopaedic surgery may be reduced to three key factors: knowledge, understanding and accuracy [111]. Publications (hopefully this included) add to the body of corporate knowledge. Competent equine fracture repair requires a trained and experienced team including imagers, surgeons, anaesthetists, theatre technicians and nurses. Accuracy is aided by technology but requires discipline, training and experience. Understanding is a never‐ending personal challenge. Technical errors are inevitable when even ‘simple’ fractures are repaired by inexperienced personnel. Technology aside, size, behaviour and temperament will always be challenges to equine fracture management. However, if the rate of progress seen in the last 50 years continues, then many of these will be met and current limitations will be confined to historical perspective.
References
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