It was an injury. He got caught under tin siding on a shelter. The top part was proud flesh. The bottom was wall torn away. I also know of another horse this happened to. He cut right through to the joint between coffin and short pastern bones. Unfortunately, this other horse had to be put down.
Young horse with sore heels.
The first thing to do is balance him medial lateral using a T square.Then shoe to 1 1\4 break over . Bring his heels back to alignment with center of cannon bone. Check diagram in under run heels. This problem is often farrier caused from trimming to much heel off. The one thing we keep forgetting is to balance the bone structure. We read about putting frog on ground so we just cut off heels with no thought to it. We must always remember to balance the bone structure!!
This horse was just a little off with slightly under run heels and out of balance medial lateral.
The owner said she couldn't believe the difference.