Adventures in Congenital Bipartite Navicular Syndrome

Poor Samson.  He is rarely featured in my blog, since he is semi-retired and semi-useless.  I don't know that I have ever really told his story, but since it has been heating up with new developments, I will give a little background.

I bought Samson in the summer of 2010 to be my confidence booster.  I stumbled across him on Craigslist, went to see him, and fell in love with his placid, easygoing nature.  Little did I know, purchasing would be the biggest "adventure" (oh, how I use that term loosely....) of my life.

A month or two after putting him into a normal workload, he started showing signs of intermittant and even shifting lameness.  After trying stall rest, extended turnout, time off, slow rehab, and everything else at our resources, we called in the vet.

The local country vet watched him go, did the first nerve block, and his lameness shifted to the unblocked foot.  We were immediately handed a diagnosis of navicular, a prescription for isoxuprine, and recommendations for shoeing.  I was distraught.  From there, we took him to a local clinic where we had a second full scale lameness work up.  Similar findings after nerve blocks - both pointed to navicular - so we progressed to radiographs.  The first x-ray was baffling.  Now, being that this was my first time even SEEING an x-ray of the equine foot, I had no clue what they were looking at.  But I quickly figured out how bizarre it was, when the vet kept on snapping multiple angles at no cost, just because he had never seen anything like it.  The first foot looked like it had fractures.  Then came the second foot, and it looked similar.  Smokey didn't know how it was even possible that a horse would fracture BOTH navicular bones, and have little more clinical symptoms other than being a "hair" off.

So, off went the rads, to NC State and Tennessee.  A few days later, the diagnosis rolled in - "congenital bipartite navicular syndrome".  Prognosis - denerving would be the best option to keep him sound and functional.

My trainer at the time was trying to reassure me that she had known of many fully functional hunters that were nerved and still in work.  In the beginning, I think I really tried to believe that one day it would be possible for Samson as well.  But it didn't take long to decide that I had a pretty strong opposition to put any more concussion on a defective bone than reasonably necessary.  So then came the palmar digital neurectomy, or "nerving", in the fall of 2010.  ****BEWARE****If you are squeamish in any way, don't play the clip - it is of a surgical procedure

I am fortunate to have a really cool, generous vet, who let me sit in on pretty much the entire procedure.  To make a long story short, we then progressed through the following 8 weeks of recovery pretty uneventfully.  Since recovering, he has remained sound and comfortable to be my flatwork and hacking companion.  I had dreams of maybe making him a foxhunter, since he is a blast out in the open, and that was my motivation to go ahead and pull a second set of radiographs to see how his wonky navicular bones were looking a year or so down the road.

Boy, did we have a bit of a surprise waiting.  We pulled x-rays of the right foot first, and when Smokey laid the current shot next to the identical shot from 2010, it was astounding - it looked remarkably better.  I was nearly jumping up and down, thinking at the moment that his body was actually trying to heal itself, to the best extent possible, and that we may have a shot at a decent career after all. 




2010 Right Navicular DP



2012 Right Navicular DP



Then came the left foot....

2010 Left Navicular DP







2012 Left Navicular DP





When examined side by side, it is progressively worse.  Noticeable even to me, the idiot when it comes to knowing anything about x-rays.  So here we are with a horse that is better in one foot, and worse in the other.  The new rads were sent back to the same clinics for second opinions, but they didn't have much to offer in the way of explanation or advice on how to proceed.

It left me unsettled, and I started asking around.  I showed the rads to a new farrier we have been trying out, and he was flummoxed as well.  They looked like a fracture to him as well.  He had not even heard of "bipartite", and he was the one who initially suggested I send them off to Dr. Hamilton down at Southern Pines Equine.

Two days after emailing them, I got an email response that Dr. Hamilton wanted to set up a phone conference.  I didn't know whether to be excited or pessimistic, because it obviously wasn't going to be a short answer.  So the phone call commenced at 4 pm yesterday.

The first thing he said to me is that my horse is "shocking."  Followed by a long pause.  He then walked through several of the x-rays, giving his notes on the changes that had taken place from 2010 to 2012.  He expressed that he wished both feet looked like the right, because we would be on the right path.  Unfortunately the left foot has him pretty concerned.  The primary concern is the amount of shifting that has taken place in the smaller section of the navicular bone.  He was overly pessimistic about the area obviously not having much stability, and about the long-term effects on soundness should the bone continue to shift.  The main concern would more than likely be the deep flexor tendon, which encapsulates the back of the navicular bone.  Basically, to make a long story short, although we nerved him to keep him sound, if this bone continues to move around it will cause damage to the surrounding areas, which will only cause the lameness to show up somewhere higher in the leg.  He will more than like be unsound again.  When, it is hard to say, since my horse is "one in a million", and there isn't much in the way of comparable case studies to base it off of.  If you so much as google "bipartite navicular" in equines, you may get a couple pages with the brief mention of it, and that's about it.  It is so rare there really isn't anything to base the next step on.

So, after walking me through so many deep explanations of the anatomy of the navicular bone, as well as the surrounding structures that could be affected, my head was already spinning.  Then he stopped abruptly, and said, "so what the heck do we DO about it?"

The first recommendation was a "drug" that is now being used in the states that has apparently been in use in Europe for years.  I instantly asked if he was talking about Tildren, and sure enough, he was.  I had heard of it being used in "navicular" cases, but knew little about the way it works.  Tildren is a biphosphonate drug that inhibits bone resorption.  In a normal horse, the composition of osteoclasts (which digest bone)  and osteoblasts (which create bone) should be fairly balanced.  In Samson's case, they are more than likely out of balance, when you look at the amount of bone resorption that has taken place in the last eighteen months.  What Tildren does is stimulate the osteoblasts, which also regulating the osteoclasts, which ultimately help the body to lay down newer or denser bone. 

So logically, after this is explained in more detail, it would make sense to want to encourage him to lay down additional bone to try to stabilize the shifting bone in the left foot, so that it will ideally attempt to "heal" itself in the same manner that the right foot has already done.

He also threw out shockwave, and explained why - that was news to me, since I thought shockwave was only used for tendons, ligaments, etc.  It apparently can be advantageous to try in the navicular area, since it is a part of the foot that naturally has poor blood supply, and since shockwave increases neovascularization (blood supply), it could only benefit the area.  But at the end of the day, the top recommendation is to try the Tildren.

He is fascinated with my congenital freak patient (as are most that come across him...) and would really be interested to see how he is affected by the Tildren, so he offered to make it as reasonable as his own costs would allow.  Sadly, the quote rolled in today, and even with the fat trimmed, we are looking at a minimum of another $1,000.

So.  That is where we sit.  And, once again, the Tildren treatment will be more or less a gamble, since there aren't really any studies of this particular nature to compare it to.  There have been a lot of successes in treating navicular syndrome with it, but that tends to have more to do with the drug affecting lesions and demineralized areas that tend to affect a "typical" navicular case.  Will it help the bipartite?  No one knows.  It's a gamble.  But it's a gamble that would possibly save him from going lame again in the future - however near or far that future may be.

Needless to say, it's been a rough 24 hours.  I don't know what to do.  I don't HAVE another $1,000 to put into this horse.  At this point I just want to keep him sound and comfortable as long as I can, and I have already invested quite a bit into that.

It was reasurring to hear Dr Hamilton commend me on even pursuing options though.  He said that there are so many people who would just throw this horse away, and I know that it is sadly true.  Not with me though.  I love that big silly guy, to pieces.  I don't know what I would do without his nuzzles or his constant antics.  But that is where we stand...pretty much at a loss.  I will keep you posted on where things progress, but at the moment, I don't know where we will be headed.