How does bone heal?

Bone Repair

1. Inflammation / Hematoma

First, when our bones are damaged, either through disease, accident, or surgery, the site of the damage will bleed and become inflamed, just as you would expect to happen with your skin. This causes a blood clot to form around the injured bone, known as a hematoma.

2. Cell differentiation

Next your body receives the message (via growth factors) that repair is required and you need more specialized cells that build bone (osteoblasts); this is called osteoblast or cell differentiation. The osteoblasts then get to work.

3. Provision of a framework

The osteoblasts need to have a structure on which to lay down the new bone; they need some scaffolding or a framework to work with. Your bone can grow across a small gap - 'bone to bone' for example in a minor break or fracture, but where there is a large gap or space then your bone may need help from doctors and science to repair itself. When this is the case, and help is required to support your body's natural healing mechanisms, you may need the help of a bone graft or bone graft substitute.

4. Remodelling

When your bone has a good framework for bone to be laid onto, and your osteoblasts have lain down new bone cells, you are left with a callous at the site of injury, in the same way as you would expect a scab on your skin when you have cut yourself. The final phase of bone repair is remodelling of this callous back to as close as possible to the bone's original shape. This task is performed by the osteoclasts.

The bone healing process can take a varying amount of time, depending on several factors:

Age of patient – older patients heal more slowly than young patients
Patient general well being – for example, smoking and obesity are thought to delay bone healing
Co-morbidities i.e. bones of patients with diabetes heal slower
Bone health – conditions such as osteoporosis may delay healing