No, certainly not. "Pressure" is a force that comes from the ground in equal and opposite reaction to the force of "weight." . . . measured in "Newtons." According to this guy Newton, the center of pressure moves in relation to the footprint on a changing vector projected on a line from the horse's center of gravity through the center of weight bearing in P3 during the loaded phases of the stride.
Could you ask him why he used a very pathological hoof to illustrate some of Duckett's priniciples? That coffin bone appears to be missing a huge chunck of its tip and appears rotated. Does the rotation of a coffin bone change the relationship of the apex of the frog and Duckett's dot to the bridge? Also, Matt's photo demonstrating the alignment of the phalanges in that sagittal view (not Russells fig 5 illustration), shows an alignment of ~ 48 degrees . If that is a rotated coffin bone, isn't it possible the the original angle/orientation could have been more like 45 degrees? Duckett claims a 54 degrees toe angle in fronts is the norm and that the coffin bone is parallel to the toe wall with the cb elevated 8-10 degrees in the heels. In this photo, it appears the outer external hoof wall is thinned back, giving the illusion of a higher (54) angle?
Eric, if you are seriously interested in Duckett's work I would be happy to provide you with his contact information. I've spent many hours discussing it with him, which I think was a good use of my time. I think it would also be a good use of your time to do the same.
I thought Duckett's work was supposed to help one in determining and achieving balance when trimming. It doesn't appear from looking at Duckett's external markers that one can easily determine if one is dealing with a more pathological hoof, ie rotated or club.
Tom, why would I need to contact dave? If a line from the center of p3 is drawn straight down, as the angle of p3 changes, the external reference points will also change. If the dot rotates with p3 then it certainly is not the center of weight bearing.
Here's a link to a free PDF of the book; save yourself $30. http://archive.org/details/handbookofhorses00doll David
I thought those revolutionary external markers (Dot, bridge etc) were to enable one to determine the location of the internal structures. On pathological hooves such as club feet or rotated one's, or sunken ones, one can not really rely on them to paint an accurate picture of what is going on internally. There are limitations to using only Duckett's concepts of the dot/bridge in determing/achieving "balance".
This quote "It is important to establish that the dorsal surface of Piii is parallel with the exterior surface of the hoof wall at the toe,..." from the DvR article linked on page two of this thread (by Mr. Burton) should show that Duckett's concepts are specifically for the average foot. If I understand it correctly (there's always the chance I'm misreading it) he is saying the first step is to determine that Piii is not rotated before you attempt to apply his concepts to the foot. David
So if in doubt, in order to determine if there is rotation you would probably need radiographs, in which case you can use the radiographs to determine where everything is internally and not need to know the dot and bridge. This hoof may not look "too bad" externally; I wonder how many would insist on radiographs. Or if the person before you has done this to the wall:
And again, there is nothing "average" about the hoof in that particular article -most hooves aren't missing a huge chunk of coffin bone tip. Why use a pathological hoof to demonstrate principles to be used on non-pathological hooves?
No. The dot and bridge are external references that correspond to internal mechanical centers. A mechanical center is mathematical entity used to describe the behavior of structural entities. What is balance? Does changing the caster/camber of a tire have any effect on the single point at the center of the axle through which all forces on the tire must pass before having any effect on the rest of the vehicle? What if the center of the axle is hollow like a pipe? Now you have a mechanical center with no structure at all. You can't see it or touch it. Does that mean that no "forces" pass through that center?
As far as I can tell from the image, the extensor and flexor tendons are still attached to P3. As such, the mechanical weight bearing center of the bone would still lie at a point mid way between those attachments as long as the DIJ remains free to articulate.
How did Duckett determine that an 8 to 10 degree heel elevation to the coffin bone is biomechanicially advantageous to the flexors? Was this something he theorized mathematically? And which flexors is this adavantageous for- the superficial or the deep, or both? Or did he just focus on the deep because of its attachment within the hoof on the coffin bone or ignore the superficial? Is this how he determined that the "normal" angle of the (front) dorsal wall/coffin bone should be 54 degrees?
Good questions. If you're serious about getting answers I would be happy to provide you with Duckett's contact information. Meanwhile I await your thoughts on the idea of forces passing through the mechanical center of a hollow axle.
I've been shoeing one like that for a few years. Full web rocker fit to match the "rocker" in the bone, matching rocker in the sole plane. Methinks it is pretty common in club foot chronic founder horses - especially Arabs.
