Hello again Eva,
How much to take off the heel?
Obviously radiographs are the best way for you to judge how much heel one is able to take off.
But for a very cheap and simple aid, I return to something that I have talked about on this forum before about using angles to estimate the positon of the pedal bone in a laminitic foot. The angle of the line of the coronet to the ground and the angle of the line of the coronet to the growth of the new growth of the front wall are remarkably consistent, in my experience.
(What is my experience? Photographs of the feet of over 200 laminitic cases, a number of which I have comparative radiographs and some of which I have cut up.
I have insufficient comparative data yet to have anything published)
Rather than go into too much detail here, I suggest you look at my website www.johnthevet.com to see the simple way to measure these angles. If you get a piece of clear plastic sheet and mark it as shown, you can either put it up against the foot or photos of it, and this will give you sufficient information about the position of the pedal bone to help you decide how much heel to take off, depending on what angle you wish to have the bottom edge of the bone.
Lynn has responded already, and I am in full agreement with her opinion about the immobility of the heels as well as her doubts about the effect soft structures of the feet can have.
Mel has pretty strong feet, the walls and bars staying relatively upright, the more heel there is the more sole that binds the heel wall and the bar together, not allowing expansion of the foot. In some cases, if I do not feel it is suitable to take the heels down all at once, I will reduce the bars sufficiently to allow some expansion of the heels - experience is needed to judge correctly how much and how to remove.
We certainly should aim for a straight hoof pastern angle, but we have to be aware that changing the heel height may well change the horse's stance. In non-laminitic horses, they will generally "stand under" if the heels are long. The hoof angle will be high, and with this change in stance, the hoof pastern angle will be straight but high. As the heels are lowered, the stance will change more sqaure - a straight hoof pastern axis, but at a lower angle than previously. In a chronic laminitic, they will very often stand with a more upright pastern while "standing square", and as they get better they will begin to stand under, as non-laminitics do.
Breakover really should be taken back further. This is sometimes liminted by the thickness of the sole, but I would be taking back as far as the foot allows. I am not sure what the concern of the farrier is about 2going over at the knees".
These can be difficult to deal with. Being of the opinion that it is the weight of the horse that causes laminal separation in the way that it does (as opposed to the pull of the deep flexor tendon), the angle of the pedal bone - front to back and side to side - will determine the distribution of the laminal separation. In my experience, the differential side to side movement will only occur when dorsal wall support is also lost.
It does seem to be a problem of ponies, with chronic laminitis, that tend to have a toe-out stance. The problem about balancing feet with this imbalance is that it may well be the natural stance for the pony. It sounds as though your farrier is trying to do just the right thing.
When trying to counter rotation of the pedal bone (front to back) we try to spread the load to the back of the foot, where the laminae are stronger, by taking the heel down. When dealing with medio-lateral imbalance, we have to aim to straighten the bone position so that the weight of the horse is shifted over to use the stronger laminae on the better side and reduce the mechanical disturbance on the weaker side.
I would be trying to have a level coronet - across the front, and the feet trimmed to have a level placement of the foot. This is, as you have found out, easier said than done.
The hind feet are better, but the same principals apply.
I hope this is of some use.