Part 3- Environmental Factors
Susan Stover, DVM, PhD, Dipl. ACVS, is the director of the J. D. Wheat
Veterinary Orthopedic Research Laboratory in the UC Davis School of Veterinary
Medicine. She is an internationally recognized expert in the field of racehorse
injuries and has spent a number of years studying the reasons for death and
injuries among racehorses in order to develop prevention strategies.
Significant progress has been made in discovering the causes of
catastrophic injury in racehorses and we now have a better understanding of the
events leading to bone fracture along with better techniques to detect stress
fractures in live horses. Stover and her team have identified race surface and
exercise factors that place horses at increased risk for catastrophic injury
and have provided horseshoe recommendations to prevent suspensory apparatus injury.
Performance horses incur a wide variety of athletic injuries that are
unique to their particular athletic pursuit. Stover and her research team are
working hard to discover risk factors, preventive measures, and effective
treatments for these athletes.
Injuries to structures that support the fetlock and digit (suspensory
ligament, superficial and deep digital flexor tendons) are the primary causes
of performance limitations in show jumpers, dressage horses, and eventing
horses. The likelihood of injury to these structures increases with increasing
limb loads, as might occur with harder surfaces or higher or more difficult
jumps. High limb loads induce extremes of carpal (knee), fetlock, and coffin
joint hyperextension and can cause damage to the supporting tendons and
ligaments.
While several factors affect limb loads and limb biomechanics, a key
factor that can be managed for injury prevention is the arena surface that
horses are performing on. There is some evidence to support the association of
surface with injury and the role of surface in limb biomechanics. Unfavorable
ground conditions (soft or heavy ground) were associated with failure to
complete the Grand National event. In a study of hoof landing in elite jumping
horses, differences were observed between sand and turf surfaces. Differences
were also found in hind-limb fetlock motion and hoof slide of racehorses
between a dirt and a synthetic track surface, and forelimb dynamics in horses
between turf and synthetic surfaces.
In elite dressage horses, fetlock hyperextension was greater on the
synthetic surface than the dirt surface (note the opposite result to that found
in racehorses).
Surface characteristics affect maximum limb loads, loading rates, and
hoof accelerations. Forces associated with these loads and accelerations spread
up the limb, with higher loads and forces causing greater joint extensions and
higher tendon and ligament strains. Superficial digital flexor tendon strains
differed in horses traveling on asphalt, sand and synthetic surfaces.
Epidemiological evidence for racehorses on flat surfaces indicates that
racetracks and race surfaces appear to affect risk for racehorse injury.
Although the results of different studies are somewhat inconsistent relative to
which types of surfaces have the greatest risk for injury, two larger scale
studies found that injury risk in racehorses was higher for dirt surfaces than
for synthetic surfaces.
In a recent study with elite dressage horses, fetlock joint and hoof
motion were compared between dirt and synthetic dressage arena surfaces. We
found that fetlock hyperextension was greater on the synthetic surface than the
dirt surface (note the opposite result to that found in racehorses). In
addition, the synthetic surface had a higher load rate than the dirt surface
(note the opposite result to that found in some racehorse surfaces). We found
that the hoof of dressage horses at an extended trot interacts with surfaces
very differently than galloping racehorses.
Not all dirt and synthetic surfaces would produce the same result,
however, because surfaces vary markedly in their physical characteristics. The
research study also measured the physical characteristics of the surfaces
because this information is most useful in designing new surfaces for injury
prevention. Thus, there is a need to customize surfaces for individual horse
occupations.
Given the high relevance and broad interest in arena surfaces and the
large financial investment associated with ring installation, the equine
community would greatly benefit from footing recommendations based on science,
with the long-term goal of establishing mixtures and management ideal for each
discipline. This work could significantly impact wastage in the industry and
reduce the need for medications to alleviate pain and inflammation in the
performance horse.
wwwhartpurysaddleryshop.co.uk
Reprinted from The Horse Report (Spring 2014) with permission from the Center for Equine Health, School of Veterinary Medicine, University of California, Davis (UC Davis).
