Page 113 - November 2021

“One pitfall in relying too much on leg boots to “support” musculoskeletal structures is based on the fact that it is much easier to limit fetlock flexion in the swing phase than to limit fetlock extension in the stance phase.”
VETERINARY VIEWS
Athletic support boots can be used in an effort to minimize damaging effects to musculoskeletal structures.
“SUPPORT” BOOTS
Research and applied technology have investigated limb protection to attenuate impact shock to joints and bones. The impact of a hoof striking the ground sets
off a series of high frequency vibrations and shock waves through the limb, potentially leading to the development of degenerative joint disease or long bone fractures. Athletic support boots have been produced in an effort to minimize the damaging effects to musculoskeletal structures.
The soft tissue structures and blood circulation of the hooves themselves do a good deal to absorb concussion to the limb. Technology has produced horseshoe polymers that further add to impact absorption.
The lower limb joints also contribute to concussion damping, but at a cost. One
area of concern is that of hyperextension of the fetlock joints as a horse loads the limb. “Support” boots allegedly provide stiffness
to the lower leg to reduce hyperextension on the fetlock joints. The degree to which this can help depends upon the materials used
in construction of the boot: the thicker the material and the more elastic it is, the greater the restriction on hyperextension.
The amount of fetlock extension determines the amount of strain on the superficial digital flexor tendon and suspensory ligaments. Injuries to these structures most often occur as repetitive strain injuries due to loading of the limb during locomotion. Reduction of fetlock extension lessens the likelihood of repetitive
strain injury. During rehabilitation from an injury, it’s particularly useful to control fetlock extension to prevent re-injury.
A horse’s tendons and ligaments play a huge role in limiting excess extension of the joints, and conditioning is critical to maximizing their effective function.
YET, WHAT THE RESEARCH SHOWS
One research project (CJ Kicker, et al, Equine Veterinary Journal, Dec 2004) demonstrated that support boots could limit the extension in the fetlock joint, thereby limiting tension on the suspensory ligaments and superficial digital flexor tendons. However, this raises the question as to how this might influence long-term effects on fiber alignment in a healing tendon. One pitfall in relying too much on leg boots to “support” musculoskeletal structures is based on the fact that it is much easier to limit fetlock flexion in the swing phase than to limit fetlock extension in the stance phase. The ground reaction force is so large that the wraps or boots would have to be very tight - so tight to risk a bandage bow – as not to loosen during work.
Another study (Drs. S.J. Wickler, C.N. Kobluk, et al) looked at the “Evaluation of Shock Attenuation in the Forelimb of Horses Wearing Boots and Wraps.” They used four groups of horses: 1) control without any boots or bandages, 2) neoprene boot lined with non- irritating nitrile, 3) neoprene boot with tendon rolls, lined with nitrile, and 4) 4-inch cotton polo wraps. Boots or bandages were worn on the front limbs, and after a warm-up period,
the horses were tested at trot and canter gaits on a treadmill for a total of 45 seconds split over three sets, with about 20 strides per set.
Based on the premise that vibrations
travel up the leg, it was expected that the
top of the cannon bone should be favorably affected by attenuation of the support boots. Instead, the research findings demonstrate that “the leg support conditions used in this study do not attenuate shock with impact.” Most studies have not shown an effect in preventing fetlock extension, and in addition, any protection effect disappears after a small amount of work. In fact, there are increases
in vibration frequencies transmitted up the limbs when using “leg support.” Although greater boot stiffness is associated with greater energy absorption, this study demonstrates that a stiffer boot also leads to higher vibration frequencies through the limb.
Other methods, such as conditioning, training, pacing, trimming and shoeing,
hold greater promise to avoid hyperextension injuries than do artificial devices like leg boots. The single greatest protection against fetlock hyperextension is by minimizing fatigue through conditioning.
Conditioning, training, pacing, trimming and shoeing hold more promise to avoid hyperextension injuries than do artificial devices like leg boots.
The impact of a hoof striking the ground sets off a series of high frequency vibrations and shock waves through the limb, potentially leading to the development of degenerative joint disease or long bone fractures.
SPEEDHORSE November 2021 111