Tonight I attended the “First Tuesday Lecture Series” at
Mr. Reilly gave a Powerpoint presentation about “hoof balance.” The main idea of his talk was that much of “modern” hoof care has not changed much in 200 years, probably the only section of New Bolton’s state-of-the-art center that could “boast” this lack of progress. Throughout Reilly's lecture, tone was one of a respect for science, and a desire for continued scientific research to back up farriery practices.
First, Reilly discussed the common measures that farriers use to measure hoof “balance:” namely, medial/lateral (side to side) generally judged by comparing the hoof wall length on the medial (inside) and lateral (outside) of the hoof; also, by whether or not the hairline is parallel to the ground when viewed from the front; and the solar view, where the amount of sole on either side of the frog is compared. Also, farriers will often sight down the hoof from behind when picking up the foot to judge medial/lateral balance at the toe and heel. Traditional farriery holds that the foot should be symmetrical on both sides, and should land flat at all gaits. Reilly mentioned that these ways of measuring balance are often in conflict with one another, presenting balance assessment problems for farriers.
Further complicating matters, balance can also be assessed in motion. Medial-lateral imbalance in landing patterns during movement has been thought to occur in the following manner: the hoof will land on one wall first, and then roll over and load the opposite wall more heavily. It was believed that this would lead to deformation of the hoof capsule due to uneven distribution of this weight..
The main bulk of Reilly's presentation was devoted to research using pressure sensitive material to record the impact distribution of shod feet on various surfaces, at various gaits. Interestingly, the data recorded suggest that the aformentioned model of loading the secondary impact wall is not accurate; actually, the horses in the study landed and bore greater weight on the same wall (outer, in both cases).
Also interestingly, the amount of loading “imbalance” in landing patterns varied depending on the gait. In both horses presented with medial-lateral loading imbalance, the halt showed more loading on the (taller) medial wall, but in the walk and trot, the horse landed first, and more heavily, on the (shorter) lateral wall.p>
Reilly then presented what he had to do in order to get the horse to land “flat:” basically, he applied a ½ inch wedge to the medial side of the hoof wall. Only this height of wedge induced the horse to land “flat,” but also meant that there was an increase concentration of pressure on the medial heel. Reilly did not recommend creating this kind of extreme “correction” in actual practice, calling into question traditional farrier attempts to “balance” the hoof using wedges. Interestingly, this previously barefoot “pasture sound” horse was already taller in the medial hoof wall, possibly beginning to compensate for its own imbalance in movement. Traditional farrier practice would often recommend lowering the medial wall to “level” the hoof, which would have actually made dynamic balance worse.
Finally Reilly presented what he considered a “sound” performance (dressage) horse. Showing images of this horse’s feet, my first impression was that the toes looked very long. Reilly chose this horse because his front and hind feet were almost complete mirror images of each other, to presumeably record the loading distribution on a "sound" horse..
This horse seemed to land toe first, especially at the extended trot. His assumption was that, since this horse was sound, a toe first landing is considered sound and normal at certain gaits. Reilly hypothesized that the toe-first landings were due to the lowering of the hindquarters which delayed touchdown of the front feet so they were no longer hyper-extended when they landed. However the long toes made me wonder if perhaps this horse either has some heel pain he is compensating for, or conversely the horse is landing toe-first because the toes have been left long in the trim and the breakover is delayed. Clearly more research, using different hoof shapes and gaits, is needed in this area.
In the presentation, it was clear that Reilly’s focus is the shod hoof; however he did mention as an aside that he removed the shoe and tested one of the hooves with just the padding beneath. He said he thought that the hoof would have shown to be less “peripherally loading” but in fact it was almost the same as shod. In retrospect, I suspect that this was because the hoof was still trimmed as if to apply a shoe, but obviously, it would be great if further study was done in this area as well.
One other interesting part of the study was the lack of pressure in the quarters of each hoof tested. Indeed, most quarters in the research did not show even the minimal amount of pressure necessary to register with the equipment. These hooves were trimmed “flat” in preparation for shoeing, with no “relief” in the quarters. I am very interested in what goes on at the quarters… something complex must be happening there. So often, bare hooves break at the quarters first… if they are not bearing weight, what physics causes this breakage? And what is the impact of different styles of trimming (a.k.a. "scooping the quarters") on weight distribution during movement?
Finally, Reilly touched on an experiment where he manipulated breakover, moving it out in front of the hoof, and also behind the toe at various intervals. He then measured the amount of pressure underneath the tip of the coffin bone. What he discovered was very interesting. As expected, when breakover was moved out in front of the hoof, pressure at the toe increased. As breakover moved back, pressure decreased, until a certain point (I believe it was past 2 cm behind the front of the hoof), where pressure at the toe began to increase again. What I suspect is that past 2 cm behind the hoof, the shoe is beginning to move behind the front of the coffin bone; I can imagine that this could produce a lever action and press the bone forward and down into the toe at each landing. Obviously radiographs and further research would help in understanding this phenomenon.
This research, while geared at the shod hoof, is definitely needed and I am excited to hear about further developments. I have heard that Hilary Clayton is using this same technology in hoof boots to measure forces on “unshod” hooves; maybe a future review will cover her research! Regardless, Reilly and I are in agreement: it is time scientific, peer reviewed studies replaced outdated habits in horse hoof care.
