Anatomy

What happens when a bone breaks?

The long bones of our legs and arms are tubular with dense compact bone tissue around the outside and soft spongy bone inside. Engineers will tell you that a tube is a very strong structure and this is true of bone. Weight for weight it is as strong as mild steel. Other bones such as the vertebrae in your spine or the bones of the foot are more like boxes with internal struts, also a very strong mechanical design. What this means is that a lot of force is needed to break bones, enough to do damage to the muscles, tendons, and ligaments as well. In fact a great deal of the pain and swelling that happens after a fracture comes from the so-called soft tissue injury, torn muscle and tendon, crushed fatty tissue, and damaged skin. There is a large volume of injured, bleeding soft tissue surrounding the broken bone causing massive bruising and swelling.

A stop-action look at what happens when a bone breaks due to an impact helps to understand this.

Bone is mildly flexible and tends to bend before it breaks. As it snaps the broken ends spring apart stretching and tearing the surrounding muscle tissue. Even if there isn’t a lot of movement (displacement) of the broken ends of the bone they bleed into the surrounding tissue causing swelling and what amounts to a large bruise.

Sometimes the damage extends to nerves or blood vessels with the potential for causing severe long-term problems. It's important for the whole treating team – led by you the patient – to remember that broken bones are surrounded by injured and bleeding muscle.

Breaks can occur in almost any point of almost any bone but some patterns are more common. Orthopaedic surgeons learn to recognize and classify these patterns because it helps to decide the best way of managing the injury. We will describe some of these patterns as we look at the causes of fractures.

Basic Terms

Closed Reduction – the fracture is treated by manipulating the pieces back into an acceptable position without surgery.

Open Reduction – the fracture is treated by surgery to put the pieces back in a good position.

Internal Fixation – the pieces of the fracture are held in position by surgically implanted plates, screws, pins or rods (implants).

External Fixation – the pieces of the fracture are held in position by pins which are passed through the a small opening in the skin, into the bone and then attached to a frame which bridges across the fracture outside the limb.

Open fracture – the fracture site is contaminated as a result of a wound which extends from the skin to the fracture site.

Closed fracture – the skin over the fracture is intact so the fracture is not contaminated.

Joint – the region where two (or more) bones touch each other and move relative to one another. The bone-to-bone contact areas are covered by a special layer called joint surface or articular cartilage which is slippery and hard wearing but which does not re-grow if damaged.

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