Osteon Summary

Getting back to this, the myriad of distractions lessened for the moment, focus back to where it needs to be, hopefully.

I had decided mere bone growth by itself probably plays an insignificant role in fracture resistance while calcification and density increases of the new growth and existing bone might be significant.

In terms of the basic structure of cortical (hard) bone, the tubular osteons--which are nicely illustrated above--the conclusion had been that in response to exercise osteons neither proliferate in number or grow in size (diameter). Instead, bone growth outward and also inward is confined to new collagen layering outside and inside the osteon complex. The further conclusion is that the cannon bone has grown, mostly as much as it is going to, early in the exercise program with the limits on growth in diameter resulting from form and function of the structures. I'd add that I suspect inward growth into the soft trabecular bone that lines the inner medular cavity housing the marrow and circulatory system probably quickly fills in with cortical bone even for mostly sedentary horses merely due to the sheer weight those bones must bear when the mature horse rises from a prone position on the ground. In any event, anyone interested how all these conclusions were reached, in the most excruciating manner, may go back and read the posts of the last two months.

What the significance of all this is in devising a training program for fracture resistance is that we may avoid consideration that we want the bones in this regard to grow in size. Rather, what I believe needs to be considered is appropriate increases in density and calcification both in view of how to maintain these qualities to the point of FR and also how to avoid losing them after they have been achieved.

Look at all this more closely in the coming posts.

Training:

Mon. 8/14 both horses were off. We are reminded of the comedy that training TB racehorses can be on Tues. morn. when our 4 yr. old Art refuses to move due to something wrong with his right hind. Normally I'd think abscess but the hoof testers show nothing. Next possible culprit is a wound the horse received about a week ago 6 inches up from the fetlock. The thing is almost healed now but there is a little fetlock swelling indicating infection. Good grief. Monitor.