I found this info and thought it was interesting:
During Fracture Healing
Fractures, or broken bones, are common injuries that orthopaedists treat. The healing process is generally the same for all fractures; through a series of stages, new bone forms and fills in the fractured area. If the fracture is severe, problems that slow the healing process can occur.
How does a fracture heal?
Stage 1: Inflammation
Bleeding from the fractured bone and surrounding tissue causes the fractured area to swell. This stage begins the day you fracture the bone and lasts about 2 to 3 weeks.
Stage 2: Soft callus
Between 2 and 3 weeks after the injury, the pain and swelling will decrease. At this point, the site of the fracture stiffens and new bone begins to form (see figure). The new bone cannot be seen on x-rays. This stage usually lasts until 4 to 8 weeks after the injury.
Stage 3: Hard callus
Between 4 and 8 weeks, the new bone begins to bridge the fracture. This bony bridge can be seen on xrays. By 8 to 12 weeks after the injury, new bone has filled the fracture.
Stage 4: Bone remodeling
Beginning about 8 to 1 2 weeks after the injury, the fracture site remodels itself, correcting any deformities that may remain as a result of the injury. This final stage of fracture healing can last up to several years.
The rate of healing and the ability to remodel a fractured bone vary tremendously for each person and depend on your age, your health, the kind of fracture, and the bone involved. For example, children are able to heal and remodel their fractures much faster than adults.