Perhaps you have heard this pseudo-fact, or ‘old wives tale’? the logic goes like this: Since we know that bones, just like muscles, grow and strengthen when worked out or put under pressure, therefore the more pressure the bone is under, the stronger it will become. This is a fact, but only up to a point. This explains why certain athletes, such as fencers and tennis players, develop greater bone mass in the arms and legs which they use more in their game; and it also explains why astronauts, under the influence of almost zero gravity, develop bone loss while in space.
However, there is no evidence that a healed broken bone is any stronger than it was before the break. The way a bone heals itself is a remarkable process. First something called a callus forms at the site of the fracture. Calcium is deposited there as an aid to the eventual rebuilding of the bone. The plaster cast which is usually put on the limb is there to protect the site so that it can heal unimpeded. And since there is actually no pressure placed on the limb during healing, the bone there actually becomes weaker, with the exception of the site where the callus is being formed, the place where calcium is being deposited.
The result of this amazing natural process is that there might be a short period during the healing process when the site of the fracture is actually stronger than the bone surrounding it. But later, when you begin to use your arm once again, the areas will reach equal strength. The place of the break is no more, or less, likely to break again. In tests done on healed fractures, the likelihood of another break was equally distributed, including along the place of the previous fracture.
I wouldn’t be too disappointed. After all, how many other things are even as strong as they were before breaking? That’s the problem with those old wives tales. They just don’t appreciate what we do have.