I bought Sport when he was four years old.
We lived in Arizona at the time. Sport was sound, had normal looking feet and xrays, and was wearing aluminum shoes with clips on all four feet. His previous owner believed aluminum shoes made him travel better in the show ring. After I bought him things were fine for a year or two before he began to develop intermmitant lameness in his feet. I had him xrayed and they showed no unusual changes. His shoes were adjusted and he was better for a while, and then became worse. Along the way I tried a number of different farriers, all recommended by local vets and having plenty of experience. I had taken a class in horseshoeing, so I had some idea of what we were aiming for independent of what I was being told by the guys under my horses. I have to say that I was surprised to find so many different, and I mean shockingly different ideas about what makes for a healthy hoof.
Tried going barefoot.
In my horseshoeing class I learned that traditional farriery suggests that all horses go a period of the year without shoes. I also knew that horses with navicular are often put out to pasture barefoot, with some measure of success in improving the problem. When we moved to Virginia, and Sport was out in the pasture most of the time I took his shoes off for a while, but because he always seemed tender-footed I had them put back on. I didn't know then what I know now about managing a barefoot horse. At this time a farrier trimmed him regularly using traditional farriery guidelines for a "pasture trim."
Tried all kinds of shoes.
Nothing seemed to break the cycle. We tried every kind of shoe you can imagine: regular, egg bar, Gene Orvnicek natural balance, aluminum, steel, with clips without clips, with pads, without pads, wedge pads, rim pads, everything followed the usual navicular cycle, Sport would improve a little and then get worse.
Tried a bunch of farriers.
In the 13 or so years I've been dealing with this I've tried 13 different farriers. Some of the changes have been due to the fact that we've moved a few times, but the rest represented a search to find someone who cold fix my horse. Let me say that to a man I believe these were honest men who were genuinely concerned about the horses they worked on and believed they were doing everything they could to make the horses sound. Almost all were recommended by the vets in the area and had years of experience working on many different kinds of horses. Still, some of the things that happened were surprising to say the least. I left one farrier when, upon his removing the shoe and dressing the hoof I could put my fingers around the hoof (placing my palm to the bottom of his hoof) and bend the whole hoof with a squeeze of my hand because so much of the hoof wall had been rasped off. Another I left after Sport mechanically foundered (vet's diagnosis) on one hoof because the toe was left too long. The last trimmed my horse to within about a 1/16 inch of the corium. This represents farriers in three different states on both sides of the country, so it can't be used as an indictment of one particular area. Unlike Great Britain, there is no minimum standard for farriers. In the UK, farriers must attend school, pass a test and apprentice for a period of time. No such national standard for education exists in this country. In the states in which I have owned horses, Arizona, Virginia, California and Hawaii, farriers regularly practice without any of these experiences. In addition, the farrier schools that do exist in the U.S. do not appear to pursue the most recent information, and mind you there has been some very interesting research recently, opting instead for practices that have been used, sometimes without any basis in scientific fact or research in my opinion, to centuries.
The last option: palmar digital neurectomy.
One of the traditional, albeit last ditch, courses of action for navicular is palmar digital neurectomy, commonly called "nerving." When everything else has failed it is possible to remove part of the nerve that serves the feet. This, of course, doesn't cure anything, it simply means that the horse won't feel any pain and can be ridden. This is a one-way road, from which there is no turning back. The body attempts to correct the situation by regrowing nerve so often the operation must be repeated, but can only be repeated a few times before the horse will have to be put down. My vet spoke optimistically of this procedure, but cautioned that in his opinion few vets know how to do it correctly. It's a major, and expensive operation requiring general anesthesia to put the on his back during the operation.