The use of commercial HBs to protect the hooves of barefoot horses during trail riding and endurance riding has gained popularity in North America.1 Although various materials are used to manufacture HBs, most commercially available boots have a polyurethane sole, a silicone wedge pad, and an outer upper covering of woven fabric.a,b Hoof boots provide cushioning and protection of the sole. The main drawback of HBs is that the distance between the toe and heels (sole length) in contact with the ground is not adjustable; consequently, horses fitted with HBs have to adapt to the manufacturer's design.1 However, the effect of this enforced adaptation has not been critically evaluated, to our knowledge. The length of the hoof or shoe may impact the breakover time, which is defined as the period of rotation of the heels around the toe in the terminal part of the stance phase. The breakover time starts when the heels lift and the hoof begins to pivot at the toe and ends when the toe leaves the ground.2,3
Shoes with a toe extension can be used to treat flexural deformity of the distal interphalangeal joint in young horses or to prevent knuckling of the metacarpophalangeal joint during advancement of the limb in horses with loss of extension function due to extensor tendon lacerations.4–6 In young horses with flexural deformity of the distal interphalangeal joint, the goal is to increase the length of the deep digital flexor tendon to correct the distal interphalangeal joint deformity.7 The proposed mechanism of action of the shoes with a toe extension in horses with distal interphalangeal joint flexural deformity is through provision of increased length of the resistance arm from the distal interphalangeal joint, thereby requiring greater strain on the deep digital flexor tendon to initiate the breakover period.4 It is speculated that greater strain on the deep digital flexor tendon results in tendon elongation and correction of the deformity.7 This proposed mechanism is based on research findings that leaving the toes long and increasing the sole length in contact with the ground prolong the stance phase of the stride and increase the duration of the breakover period of the foot, thereby resulting in strain on the deep digital flexor tendon.2,8 However, the kinetic effects of shoes with a toe extension in healthy horses have not been investigated, to our knowledge.
In recent years, there has been an increased demand for horseshoes and protective devices for feet to allow horses to remain free of lameness.1 Horse owners and trainers have used HBs to maintain their horses’ bare feet and protect the hooves and soles during daily exercise.1 Also, some clinicians recommend the use of HBs for horses with hoof wall defects, signs of foot pain, solar puncture wound, or laminitis because the HBs provide sole support and shock absorption when the feet contact the ground, as well as the capability to elevate the heels, thereby relieving static tension on the deep digital flexor tendon during weight bearing.9,10 It is our clinical impression that HBs provide cushion support to the foot and decrease the vertical ground forces on the feet, which allow horses with acute or chronic signs of foot pain to be more comfortable while wearing the HBs. However, to our knowledge, the kinetic effects of the HBs in healthy, nonlame horses have not been investigated. We speculated that the use of HBs may alter the GRFs in nonlame horses during walking; therefore, investigating the locomotor forces during the stride may provide objective data to determine whether HBs have any effects on the GRFs of normal horses.
Force plate gait analysis is an objective method for measuring the reaction forces between the hoof and ground (ie, GRFs) and stance duration in nonlame and lame horses moving at different gaits.11–14 Furthermore, force plate data can also be used to determine the time at which peak GRF occurs, the impulses expressed as area under the force-time curve, and the point of application of the force (center of pressure) underneath each hoof.14 Force plate gait analysis is a reliable and repeatable means of assessing limb function, lameness, and the effect of different shoeing regimens in horses.15,16 The gait in horses can be affected by shoeing and by different types of shoe or hoof protective devices applied.4,17 The purpose of the present study was to investigate and compare the effects of popular commercially available HBs and shoes with a toe extension on the stance duration, GRF, and sole length in contact with the ground in nonlame horses during walking. It was hypothesized that in healthy horses during walking, application of HBs or toe-extension shoes would increase sole length in contact with the ground but would not modify the vertical or longitudinal (braking and propulsive) peak forces, compared with findings derived when the horses were barefoot.
Supported by the Department of Clinical Veterinary Medicine, College of Veterinary Medicine, University of Illinois.
Ground reaction force
Soft-Ride Equine Comfort Boots, Soft-Ride Corp, Vermilion, Ohio.
Easyboot Rx, EasyCare, Tucson, Ariz.
Anti-Fatigue Mat, 9RHZ4, Grainger, Palatine, Ill.
Infrared photoelectric sensor, MEK-92-PAD, Mekontrol Inc, Northborough, Mass.
Force plate, EQ6001200–4000, AMTI Inc, Watertown, Mass.
Acquire, version 7.33, Sharon Software Inc, Owosoo, Mich.
Kodak Carestream Pacs, version 11.3, Carestream Health, Rochester, NY.
PROC MIXED, SAS, version 9.3 for Windows, SAS Institute Inc, Cary, NC.
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