How long does it take for a broken bone to heal?
There are a number of variables in that equation, depending on where the break occurred, and how serious it is. A hairline fracture, for example (very small crack in the bone) can heal quite quickly, whereas a compound fracture (bone completely broken and separated) can take months. A typical broken arm or leg usually takes about six weeks in a cast, and sometimes some therapy afterwards.
It also makes a difference if it's a rib or an arm, versus a backbone or your neck. Any break associated with the spine or skull is going to take longer.
As young people are still in the growth phase, it sometimes doesn't take them as long to heal bones as an elderly person, who doesn't regenerate as quickly. A joke in the medical profession with regards to children's injuries goes something like: If the bones are all in the same room, they'll heal.
It depends upon the age of the person, the type of fracture, and the general state of health. Bones heal faster in the younger age group and in someone who is relatively healthy. Lets say you broke or fractured the radius of the arm, if your orthopedist puts a caste on the arm, you will have to wear the caste for 6-8 weeks generally. After this time period the caste will be removed, this means that the bone has healed sufficiently to take the caste off, the integrity of the bone is intact. However, continued healing takes place over the next couple of months (assuming you don't re-injure the bone).
More complicated fractures or those that required surgery take much longer to heal. If the person is in a poor state of health, the fracture takes longer to heal.