YOUR HEALTH - MEDICINE 101

FRACTURES

I've got a bone to pick with you. The word "fracture" simply means a break, a disruption in the continuity of a bone. There's no difference between a broken arm or a fractured one but there are many types of fractures.

They all fall under one of 2 categories - compound or simple. A compound fracture cuts through the skin - it's kind of nasty and you should try and avoid that. A simple one doesn't break the skin. Fractures can be complete, where the bone is broken right across, such as this one, or hairline where the break may not extend all the way. A common fracture in children is called a greenstick. Children's bones are much more malleable and able to be stretched just like this stick. Break a fresh one off a tree and you can't break it directly across - only one side of the stick fractures.

Another way to classify fractures is in their alignment, the relationship of one part of the bone to another. This is a displaced fracture - the bone fragments are out of their usual alignment. An undisplaced fracture means that the pieces of bone are still in the correct positions.

The minute you break a bone, blood leaks out from the bone marrow (the centre of the bone) in between the fractured pieces. Then new blood vessels grow, producing collagen fibres. It's like a foundation of scar tissue. Next, the fractured ends of bone produce new bone cells that begin to re-establish the continuity of the bone and bridge the gap. That forms a cuff of new bone called a callus. You can see on this model, it actually covers 360 degrees of the bone. It's easily visible on X-ray. (if there is no x-ray - cut preceding line)

Its this callous that gives the bone its solidity. And it takes only six weeks for many fractures, much shorter in children. But the process goes on for a couple of years as the bone is remodeled and the callus on the outside is reduced. This remodeling process will actually change the angle of the fragments, it will re-align them. You can see it here. The original fragments of the original fracture are displaced, but with the passage of time the bones have come into a much better alignment.

All we doctors do is slap on a plaster cast. That immobilizes the bones in the correct position and helps with the cellular repair. So go ahead, break a leg. Your cells have got you covered.