Thursday, 19 January 2012

Hoof imbalance - how it affects the parts you can't see

I've been trying to come up with a way to illustrate what happens when hooves get out of balance, but I haven't been able to find any pictures that do what I need.  

The problem is that I have therefore had to get out my crayons and start drawing - which as you can see is not my strong point.  Needs must, however, and I just hope you can make out enough for these to be useful(!) - you can click on them to enlarge. 
This is a fairly familiar side (lateral) view of a hoof showing P2, P3 and the distal sesamoid (navicular) bones with the collateral ligaments which connect them in blue and orange.  These ligaments, plus the deep digital flexor tendon (in green) commonly show up on MRI as the problem areas in horses who have caudal hoof pain or navicular bone damage on x-ray. 

From the palmar view (ie: as if you were behind the hoof and looking towards the toe) it becomes more obvious why the medio-lateral balance of the hoof is crucial and why those ligaments have to be evenly loaded and balanced for the horse to be comfortable.  
Although ligaments and tendons can't be seen on x-ray, it is possible to see how poor medio-lateral balance affects the hoof.  The blue lines show the angle of the old hoof capsule.  The green lines show the ground line compared to the alignment of P3 and you can see that they aren't parallel.  

This has led to strain on the collateral ligaments which was confirmed on MRI.  In this horse, the problem was caught very early but if this sort of imbalance continues for more than a short while it can lead to ligament damage (and eventually bone damage) as well - of course - as long-term lameness. 

This isn't primarily a trimming problem - in this horse's case the foot was already short and any attempt to trim or shoe the foot level would have been invasive.  

However, when the shoe was taken off and the horse came for rehab, she started to grow a hoof capsule (the red lines) which followed her bone alignment.  Over time, this has corrected the medio-lateral imbalance internally, as you can see here now that the whole hoof capsule has grown in.  


jenj said...

Your drawing skills were perfectly excellent for illustrating this point!

I have NEVER seen the palmar view with the tendons drawn in, and now it makes perfect sense as to why the ligaments are strained. Lightbulb moment!

This is probably a really obvious question, but how do you know if the hoof is balanced? I know from your blog that a hoof that's balanced for the horse may look imbalanced to us. Is there any way to tell other than rads?

Nic Barker said...

Thanks Jen :-) I had to have a few attempts but like you I couldn't find the right illustration anywhere else - just bones, or bones plus DDFT but not the coll. ligs. Glad it made sense to you!

Yep, there are lots of other indicators - the main ones are frog orientation, sole symmetry and collateral groove depth - food for another post, methinks!

Funder said...

Great illustrations. The anatomy images I've found online usually have way too much detail or way too little - those were perfect.

So if I'm understanding this case study - the mare had wonky internal structures, but she was shod "level" and "balanced", which led to strain on the collaterals? Now that she's grown a lopsided foot to match her bones, she's going sound?

Sigh. So scary.

Nic Barker said...

Thanks, Funder. The mare in the photos and x-rays is a mare called Lucy who was here last year, and the photo is one her owner sent as an update recently. She has been back in work nearly a year now and has completed an affiliated ODE as well.

She had been shod to the x-rays and MRI and these were the 2nd set of x-rays, taken after (I think) 2 shoeing cycles which were supposed to show an improvement in m/l balance. In her case, at least, the remedial farriery had been unable to improve things - I have a theory as to why but will blog about that another day - so much to blog about, so little time...!

Neets Human said...

would proprioception be wonky too.. ?just thinking about how we subconsciously balance our foot falls to terrain and our own anatomy..

PS great drawing.. I do have a book that almost does what you did but not quite!

amandap said...

Fab! I'm trying to get to grips with tendons and ligaments atm so this is a great post for me.

Any chance of blogging about wall ripples at sometime in the future? He he.
Chop this question off if you wish.

Nic Barker said...

Thanks NH, and I think you are dead right about proprioception.

Yes, Amanda, I am taking requests shortly for next week's blog topics ;)