These ilustrations showing the bones without the stuff attached to them don't do a good job of showing the distortion that happens in the coronary region during founder. The extensor tendon attaches to the top of PIII adding to it's bulk. When PIII rotates and/or sinks, it's upper tip (extensor process and attached tendon) is forced into and/or sucks down with it that which normally resides happily in the coronary groove (the coronary corium/plexus).

Thus compressed/distorted, the function of the coronary corium/plexus is impaired to some degree, depending on the amount of PIII displacement.

When left in this state the anterior aspect of the hoof wall's growth is inhibited, usually more than the quarter/heel aspect, causing slower growth at the toe and normal or sometimes accelerated growth in the quarter/heel region. This unequal growth pattern causes the characteristic dished toe. In this ilustration the toe has been partially "set back", but not nearly enough. The heels have been left too long in my opinion. my goal when trimming a foundered hoof is to restore the bone to it's normal (pre-founder) position. In this case the toe would be set well back, the lamellar wedge would be removed, the heels would be lowered to their normal hight, and a heart bar shoe would be used to push PIII back into it's proper position. One could say that this is merely proper shoeing of the bone, rather than shoeing the hoof wall, if one wanted to say such a thing.

It is the purpose of the Heart Bar Shoe, or some PIII support scheme, to replace PIII to it's rightful home in order to reestablish hoof health.