This was a mare at our rescue, she had a canker that swelled up and broke off the heel of her hoof. Rood+Riddle came and did an experimental surgery to remove the remainder of the canker. It worked. We kept it in a boot and soaked it regularly in hydrogen peroxide. It grew back completely, the frog is a bit mishappen, but other than that it's a solid, working hoof. She's completely sound on it!
Holy cow Copperhead! I've never seen an exposed coffin bone and wall separation before. That's amazing that could be healed at all. That horse was very lucky to find the right person.