Re: Cannon Bone measurements

[Tivers@aol.com]

In a message dated 98-01-31 12:44:19 EST, CMKSAGEHIL writes:

<< I think the density issue relates more to a QUALITY of bone that is
impossible to measure with a tape measure but is evident in the eye of the
experienced horseman as clean, flat bone.  I know I have found a strong
correlation between structure that I admire and whether I see that horse back
year after year on the circuit, and I don't tape all those horses as I vet
them in...  I know there have been some radiographic studies done about this,
too, and while I can't recall the bottom line, I remember finding them
interesting.  Tom, do you have any more info about that?
 
 Heidi Smith, DVM--Sagehill Arabians (Oregon) >>

The bone remodels to accommodate the stressors it encounters--these in
racehorse being bending and twisting forces, mainly in the forelegs. A paper
in the German AESM symposium outline a procedure for measuring the strength of
the shape of the cannon bone using x-rays--basically, the front of the cannon
bone should be twice as thick as the back part of the bone--an oblong donut.

We spent some time using the NIBBs system of through and through ultrasound
for measurement of bone density. That's where the "big bone is soft bone"
concept comes from. In young horses going into training the changes are quite
dynamic. One thing we found is that a high stress workout will cause a
decrement in bone density that is half paid back in a week and back to normal
in two weeks--all this from 1/4 mile of maximum effort. 

A progressively loaded exercise regime, where speed is increased slice by
slice avoids most problems unless the horse has very heavy bone. In that
case,not only are the cannon bones soft and subject to injury, but the joints,
too are easily damaged. There are some vets using an aluminum block that is
graduated in thickness next to a bone for x-ray density estimation. Due to
variations in x-ray technique, this is difficult to accomplish and quantify.

Using infrared thermography, we can see the preliminary signs of softness in
the lower legs--splints coming on, inflamed areas on the cannon bone, joints
heating up, etc. That's my best diagnostic tool. 

ti