Forces Stressing Bones

Tom Ivers used figures of 10,000 lbs/sq. inch to 12,000 lbs/sq. inch as as the force working on the cannon bone at speed. The illustration below provides visualization.

Unknown where Ivers got the 12,000 lbs/sq. inch figure as I've yet to see any studies or other verification, but, just read a human doc saying that our tibia's undertake 1200 lbs/sq.inch of force at the run.

In discussing the physiology again start with my disclaimer that this is a blog instead of scientific dissertation, based on googling, memory and connecting the dots.

I'm in good company though. Google the cause, studies, process of equine fractures in wake of the enormity of the fracture problem, and what do you get: nothing, other than articles on fracture repair. It seems besides brief speculations in peripheral studies our good vet schools have yet to undertake any comprehensive study of the manner and method of equine racing fractures, at least that I've been able to locate.

So, absent any equine studies, I'll turn to some human ones which provide the illustration above and those to come.

I'm conjecturing that the force working on the cannon bone of our mythical chestnut at speed are:
1. Tendons and ligaments pull and push the bones around at tremendous force and speed. They move 1000 lbs+ down the track at 40 mph. Consider the pure force of this rapid forced motion particularly on the smaller bones, the sesamoid and pasterns, and also on the ephyseal bone edges of the cannons so subject to condylar fractures.
2. Weight bearing at speed, which is the compressional force in the above illustration.
3. Ground forces at speed, which are the tensile forces in the above illustration.

So, if we're visualizing the process of forces working on the bones at speed what we'll see is a combo of forces coming from all directions caused by weight coming from the horse combined with concussion from the ground as well as the tremendous force generated by the muscles of the horse moving the enormous weight at great speed. So where does Ivers 12,000 lbs/sq.inch come from? Consider 1000 lbs + motoring down the freeway on bamboo thin legs at 40 mph. It's a scary thought.

I'll take a little closer look at this next post.

Training Interruptus : Still raining Saturday night. Below is fog-shrouded downtown KCMO this Sunday morning. (u'd have to left click to enlarge and scroll to see the city. its in there somewhere.) Maybe some sun yet today to dry up this mess.