What causes bone fractures to itch?

Mine too.. I have a broken collar bone (left clavicle) and it itches so much.. I even have small blisters.. they do not hurt though.. maybe it is due to inflammation as Anubhab says.. here is what the internet came up with: In Chinese medicine, the healing process of fractures is divided into three distinctive stages, each lasting about two weeks: 1. Acute Stage This stage occurs during the first and second weeks after the fracture takes place. The first seven days are accompanied by acute pain and swelling. A pool of blood is created from broken blood vessels around the bone. This pool of blood starts to produce bone cells within the first seven days. In the second week, the bone starts to knit. This process can cause discomfort and itching, especially at night. 2. Knitting stage This stage occurs during the third and fourth weeks after the fracture takes place and continues the processes started during the acute phase. As bone cells continue to be formed, so does the bone knitting. Even though the affected bone may have completed knitting by the fourth week, it will likely remain flexible and soft at the point of the fracture. 3. Complete Healing This stage occurs during the fifth and sixth week after the fracture occurs. If the person is healthy and the break is one of the less complicated types of breaks, then the affected bone has most likely regained it’s strength and solidity as the sixth week draws to a close. On the other hand, complete healing of severe and complicated breaks can take longer. Of course, appropriate treatment immediately following the break and thereafter can greatly expedite the fracture healing process. Here is where I got it from: http://sinewtherapeutics.com/fractures-fracture-healing-and-types-of-fractures.html

I really don't know. The chemicals which make a healing skin wound itch (histamine, cytokines) work by stimulating skin receptors and itch fibres which are not present (or at least have not been identified) in bone and I've never previously heard of a fracture (as opposed to the skin under a cast) itching. The same applies, for example, to a heart attack - the same inflammatory process occurs but I've never heard of anyone reporting an itch. Perhaps a variant of synaesthesia?

Your body's first response to a fracture or any injury is inflammation.  Therefore there will be more fluids (and other substances such as white blood cells) in the vicinity of the fracture.  This means that the volume of that part of the body is greater.  Therefore the area around the fracture will swell.  This stretches the skin.  Stretched skin itches.The same phenomena explain fracture blisters.

Itching is a very common phenomenon when areas of the body are healing, and sensory nerves are regenerating. As the cells bridge the gap caused by the break, the generate the itch response.

Itching is a mild pain sensation. Is it the feeling of nerves irritated or bones knitting back together? Idk, sorry. 

A pool of blood is created from broken blood vessels around the bone. This pool of blood starts to produce bone cells within the first seven days. In the second week, the bone starts to knit. This process can cause discomfort and itching, especially at night.

The itching is caused from the healing and internal inflammation that is involved with the healing process.

Many good answers I can say that it means it's healing. But that maybe wrong. My husband broke his ribs 7 years ago and his back still itches. Sorry