Growing up I always heard the same adage when I broke a bone, “Don’t worry it’ll grow back stronger”. But is that really true?
Bone healing is less of an absolute state of ‘healed’ or ‘broken’, and more of a continuum from ‘not healed to quite healed’. The healing process of bones is pretty complicated, but can be broken into 3 phases: The reactive phase (during which the area around the break swells), the reparative phase (during which the membrane that covers your bone converts itself into bone and cartilage cells and starts bridges the gap between broken bone segments) and the remodelling phase (wherein the trabecular or temporary bone is replaced with compact permanent bone). It’s this last phase that complicates saying when a bone is healed, because it can take between 3 weeks and 5 years!
During the reparative phase a mineral deposit at the site of the break is formed called a callus. This calcium collection is really strong, so, while the bone is healing there is a period when the break site is stronger than it ever has been. But, the rest of the bone surrounding the break site actually demineralizes because of inactivity (since you’re probably in a cast). So the bone overall weakens during the healing process.
When all is said and done the bone will return to basically the strength it was before you fell off your bike, no stronger, or weaker.