Yesterday!

...we had a meet here because it was my birthday - I was trying to keep quiet about age but someone had other ideas!! We had a really fantastic day - thanks to everyone who came, everyone who helped, and especially to my brother Jon and nephew Samuel who slaved over sandwiches, cake and sausages all morning :-)

Changing hoof loading

More rehab photos, another new arrival who is growing a new hoof capsule at an impressive rate. As you can see from the (sorry, slightly blurry) upper photo, he has poor medio-lateral balance, confirmed by X-rays.

In shoes, his hoof was shunting laterally and collapsing medially, but if you look at the new hoof angle, and project where the hoof capsule should be when it has grown down, he will have much more medial support, which over the longer term should improve his soundness.

The top band of new growth really is growing in at that angle, its not just a camera angle - in fact in real life the difference is even more dramatic - and this hoof growth has developed in less than 4 weeks, and despite the fact that he is not able yet to do much work. He has a very weak and under-run caudal hoof but this is also slowly starting to strengthen, although that process will be a long time.

Frog development

Thought these shots might be interesting, keeping the theme for the week(!). This is a horse who is here for rehab at the moment, the lower photo LF the day he arrived, the top photo same foot after less than 3 weeks.

He has weak frogs, of course, and no digital cushion to speak of, particularly on this foot, but frog stimulus is key to getting a healthier caudal hoof, and he is making a good effort to improve himself :-)

Hoof loading - shod and barefoot comparison

One good thing about having snow is that there are lots of hoof prints to look at - an endless source of fascination for a hoof-anorak like me! Often, the snow means that shod horses can't venture out, because its just too dangerous, but the snowfall last Friday was so light that for once you could see the barefoot and shod horses' hoofprints side by side.

The close-up shots make the difference in how hooves load crystal clear, and also highlights the factors I blogged about earlier in the week.

The weight of the shod horse has been taken peripherally, by the rim of the hoof; the frog has taken almost no weight and has barely touched the ground.

By contrast, the weight of the barefoot horse has been taken caudally, by the heel and frog, with the hoof wall sharing the load as the limb moves towards breakover.

If you think about the weight of the horse's body, held up by the bony column of the leg, its easy to imagine which loading option gives greater stability, support and shock absorption. Its also very clear how much smaller the loading area is for the shod foot, putting a much greater strain on the edge of the hoof. The barefoot horse, by contrast, has a huge surface area over which to spread the load.

These photos really illustrate the effect shoes/barefoot may have on bone stimulus, I think - as I posted on the 2 blogs earlier this week - http://rockleyfarm.blogspot.com/2010/02/stress-shielding-more-about-bones-and.html and http://rockleyfarm.blogspot.com/2010/02/reversing-navicular-bone-damage.html

FWIW, I am not taking bets as to which horse has the healthier bones, even though the barefoot print is from a horse is who is 25 years old!

Stress shielding - more about bones, and shoes

While I was following up research on bone regeneration that I blogged about on Monday (http://rockleyfarm.blogspot.com/2010/02/reversing-navicular-bone-damage.html), I came across an even more interesting fact from research into human biomechanics.

As with bone regeneration, its something that you could discuss with a medical doctor and they would simply say - "Duh, of course - thats nothing new"...BUT I don't think its crossed over into equine veterinary research yet. Maybe I am wrong, so if anyone can point me at any studies, PLEASE do so!

Its common ground that bone forms in response to mechanical load, so the stresses and strains which the bone receives from movement and its environment are critical to its strength.

What is mind-blowing (but when you think about it, not surprising) is that if you replace or support a bone with a stiffer material, like metal, then the stiffer material becomes the primary load-bearing structure. This reduces load to the bone and it degenerates in response.

This process is called "stress shielding" and it has received a lot of attention from researchers into human medicine, because bone degeneration is a consequent problem in patients with hip or knee replacements, and its also a factor when fractures are repaired with metal plates.

I had a lightbulb moment when I read about this, because stress shielding may well be the one of the factors affecting shod hooves.

Bob Bowker is already starting to look at pedal bone density in cadaver hooves, and is postulating a link between peripheral loading and osteoporotic bones - his article is here.

The question is whether shoes are also causing stress shielding; if so, this would be another way in which bone density could be adversely affected. Changing both the loading of the hoof and removing the stress shielding should therefore lead to bone restoration over time.

What we need, of course, is research into how seriously bone density in horses (particularly navicular and pedal bone density) is affected by shoes, and whether its possible (and how long it takes) to restore density in a correctly loaded, unshod hoof.

In humans, it used to be thought that bone loss due to stress shielding peaked 2 years after an implant, but now its thought to continue indefinitely. Its also a common cause of pain for human patients and there is no reason why this shouldn't also be true for horses.

Meanwhile, I am posting photos tomorrow which illustrate things quite nicely :-)

Reversing navicular bone damage

There is a common belief among horseowners and vets that once a horse has navicular bone damage, that damage is degenerative - it will get worse over time and cause the horse increasing lameness.

Perhaps this is partly due to the traditional view that navicular bony changes were the cause of the lameness; in fact we now know that they are a symptom, and usually only occur once the horse has been lame for a while, but you can still find lots of textbooks and websites which describe navicular as a degenerative bone condition.

Our own horse, Ghost, was diagnosed with navicular in 2000, on the basis of nerve-blocks and X-rays which showed mild bone damage. He has been sound and in work barefoot for many years now, and in 2007 we had him X-rayed again, only to find (as we expected) that his navicular bone no longer showed any evidence of damage.

If you think about it logically, you would expect that, as poor biomechanics can stress soft tissue and lead to inflammation and eventually bone damage, correct movement and loading will over time allow the bone to strengthen and remodel. Its a process which is well understood in human orthopaedic medicine, after all:

"in a deformed bone the internal structure was radically altered as a response to the static forces working on it. A normal bone will alter to meet a change in its function. If such change in mechanical environment is rectified, the bone will resume its former shape and structure."

JSR Golding

Its no coincidence that these types of horses show caudal hoof pain and are landing toe first - as well as the soft tissue damage which they will show on MRI, the reduced loading of the caudal hoof is bound to affect bone as well:

" when the loads are increased over normal levels, bone mass is increased, and when the loads are decreased, bone mass is lost"

MCH van der Meulen, P J Prendergast

This is a fascinating area, and I've got lots more about this tomorrow and Wednesday :-)

Caught out!

Andy made the tactical error yesterday of setting out from home in a 2 wheel drive car...

...this meant that last night he had to abandon it 3 miles from Rockley and walk up the hill by the light of the silvery moon...

This morning, of course, there is no chance of retrieving the car, and there is MORE snow forecast later today. Horses are quite happy about this, apart from the lack of hunting, but its is becoming a little inconvenient, even with 4WD...