I usually try to work with the vet at the time the x-rays are taken to assist if possible.When taking the lateromedial radiographs the focal point must be centered on P3. A radio-opaque marker, of known length, is placed sagittally on the dorsal hoof wall with the top of the marker aligned with the coronet atthe point where the hoof horn turns from hard to soft. A second marker, usually a thumb tack, must be placed sagittally in the frog; it’s position must be marked on the foot – usually with a permanent marker (we draw a line across the sole and frog to mark this position.)
The tack is normally placed about 3/4 of an inch behind the apex of the frog, but exact placement is not necessary – this marker just gives us a point of reference on both the image and the foot. This measurement is used when custom crafting and placing the shoe if deemed necessary. Once we have the correct images (no obliquity etc) we can quantify the extent of the disease.
Data gathered from the images includes the distance from the coronet to the extensor process of P3, Sole depth, sagittal length of P3, amount of bone degeneration (if any), and hoof wall thickness. Other data can be gathered but are not needed. The dorsal marker is used to correct for magnification.
Once the data is gathered and corrected for magnification we compare to a known set of normal parameters for a quantification of the extent of the disease. At this point if it is determined there has been distal descent or wall thickness outside normal parameters, I recommend the placement of a rigid positive pressure heart bar shoe. We then determine exactly where to place the toe of our shoe and where the tip of the frog plate must go. The shoe is built to specifications and correct fit is tested at the foot. Once the shoe is spot on we build up the frog plate with fast setting urethane to achieve positive pressure.(At the foot side of the shoe the frog plate will be higher than the outside of the shoe so that when it is nailed to a trimmed foot it pushes up on the frog. this is the tricky bit….getting the amount of pressure right takes experience and an artistic feel.) The positive pressure rigid heartbar mechanically prevents the bones from descending if fitted correctly. Pre/post radiographs have shown that in severe cases it can cause the bone column to ascend within the hoof capsule and bring us closer to normal alignment. Even if the patient is recumbent the shoe, via the positive pressure, continues to prevent distal displacement of the bones. I hope this explanation helps give you an understanding of the process from my perspective.