Summary This study quantifies both the intended effect of orthopaedic shoeing to decrease the load on the navicular bone and the eventual undesired effects on gait performance. The compressive force exerted by the deep digital flexor tendon on the navicular bone and on the quality of the trot and redistribution of forces over the flexor tendons and the suspensory ligament were studied as a function of orthopaedic shoeing in 12 sound Dutch Warmblood horses. A modified CODA‐3 gait analysis system and a force plate were used to quantify objectively the load on the lower limb. The quality of the trot was assessed using the same gait analysis system while the horses were trotting on the treadmill. The effects of shoes with heel wedges and egg‐bar shoes were compared to flat shoes and unshod feet. When heel wedges were applied, the maximal force on the navicular bone was reduced by 24% (P<0.05) in comparison with flat shoes. Egg‐bar shoes did not reduce the force on the navicular bone, but in unshod feet this force appeared to be 14% lower (P<0.05) compared to flat shoes. Egg‐bar shoes cause the horse's trot to be slightly less animated (P<0.05), compared to flat shoes and shoes with heel wedges. It is concluded that shoes with heel wedges reduce the force on the navicular bone as a result of a decreased moment of force at the distal interphalangeal joint in combination with a decreased angle between the deep digital flexor tendon distally and proximally of the navicular bone. Therefore it can be expected that in horses suffering from navicular disease, heel wedges will have the expected beneficial effect on the pressure on the navicular bone, while the effect of egg‐bar shoes remains doubtful.

The objective of this study was to provide normative data describing the net joint moments and joint powers for the stance phase of the forelimb in trotting horses. Kinematic and force plate data, synchronised in time and space, were collected for the right forelimb of 6 Warmblood horses moving at a trot. The 3-D kinematic data were collapsed onto a sagittal plane, and were combined with the vertical and longitudinal ground reaction forces and with segment morphometric data to calculate net joint moments in the sagittal plane across the distal interphalangeal ( c o a ) , metacarpophalangeal (fetlock), carpal, elbow and shoulder joints. The joint mechanical power was calculated as the product of the joint moment and the joint's angular velocity. Major peaks on the moment and power curves were identitled.Each joint showed consistent and repeatable patterns in the net joint moments and joint powers. During most of stance the net joint moment was on the caudaYpalmar side of all joints except the shoulder. At the coffin joint the power profile indicated an energy absorbing function that peaked at 74% stance, which coincided with the maximal longitudinal propulsive force. The fetlock joint behaved as an elastic spring; energy was absorbed in the first half of stance as the flexor tendons and SL stored elastic energy, which was released in the second half of stance as a result of elastic recoil. The carpus did not appear to play an important role in energy absorption or propulsion. Both the elbow and shoulder joints showed what appeared to be phases of elastic energy storage and release in the middle part of the stance phase, followed by a propulsive function at the shoulder in the later part of stance. The fetlock, carpus and elbow showed virtually no net generation or absorption of energy. The net energy generation at the shoulder joint was approximately equal to the energy absorption at the coffin joint.

In horses with experimentally induced superficial digital flexor tendinitis, changes in vertical GRF were reflected in angular excursions of the distal interphalangeal and metacarpophalangeal joints, whereas changes in longitudinal GRF were associated with alterations in the protraction-retraction angle of the entire limb.

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Summary An in vitro model was developed and validated in vivo to quantify the attenuation of impact vibrations, transmitted through the lower equine forelimb and to assess the effects of horseshoeing on this attenuation. The transsected forelimbs of 13 horses were equipped with custom‐made hollow bone screws in the 4 distal bones, on each of which a tri‐axial accelerometer could be mounted. The limbs were then preloaded while the impact was simulated by dropping a weight on the steel plate on which the hoof was resting. At the hoof wall, the distal, middle and proximal phalanx and at the metacarpal bone, the shock waves resulting from this impact were quantified. To assess the damping effects of shoeing, measurements were performed with unshod hooves, hooves shod with a normal flat shoe and hooves shod with an equisoft pad and a silicone packing between hoof and pad. The in vitro model was validated by performing in vivo measurements using one horse, and subjecting the limb of this horse to the same in vitro measurements after death. Approximately 67% of the damping of impact vibrations took place at the interface between the hoof wall and the distal phalanx. The attenuation of impact vibrations at the distal and proximal interphalangeal joints was considerably less (both 6%), while at the metacarpophalangeal joint 9% of the amplitude of that at the hoof wall was absorbed, leaving approximately 13% of the initial amplitude at the hoof wall detectable at the metacarpus. Compared to unshod hooves the amplitude at the hoof wall is 15% higher in shod hooves. No differences could be observed between shoe types. At the level of the first phalanx and metacarpus the difference between shod and unshod vanished; it was therefore concluded that, although shoeing might influence the amplitude of impact vibrations at the hoof wall, the effect of shoeing on the amplitude at the level of the metacarpophalangeal joint is minimal.