How Bones Repair

Last week I wrote about wounds healing.  The last stage of healing is remodelling, when bones are broken they too will remodel!  See my blog about bones from a couple of years ago to understand more about the composition of bone.

When bones break cleanly they are often able to return to their original shape if:

·         the opposing ends of the bone are in alignment

·         the blood supply is adequate

·         there is no infection

·         there is no extra stress on the injury

As with wound healing, a blood clot will form around the break,  polymorphs take away the bone fragments as well as any bacteria.  Osteoclasts will then dissolve the old bone cells and damaged tissue.

Next the cells of the periosteum (protective membrane around the bone) will replicate and change into chondroblasts and osteoblasts.  The fibroblasts in the granulation tissue (see last week's blog) also change into chondroblasts, these cells form hyaline cartilage.  The osteoblasts form new bone cells.  The initial bone cells which form are only temporary.  The hyaline cartilage and new bone  increase in size until they fill the gap (where the fracture is) thus forming a lump or 'fracture callus'.  The bone now has SOME strength but not much.

The next stage of healing is when the hyaline cartilage is converted to bone and the new bone cells are replaced by stronger, bone cells.  

Finally, the remodelling process takes place, when the bone cells are changed into compact bone - which is much stronger - and the 'fracture callus' is altered to closely resemble the bone before the break occurred!   

This can take several years.

As with humans, how long it takes and how well  a bone heals depends on where the break is, how old the horse is and many other factors.

Have you seen this week's video 'Autumn..so it begins' on my You Tube channel?  
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Until next time!

Jo