I saw some videos the other day about arm wrestling and broken arms. I wrote a post suggesting that the bone density problems that are now so popular are a modern problem because physical exertion has become less of a part of daily life, but also because of a medication and processed food way of living (especially now with aspartame, MSG, etc.). No doubt, the Vegan fad, etc. (absence of dairy) also contributes to the loss of bone density.
I always thought that the calcium explanation was too much of a 'wives tale' based on the simplistic observation that bones contain calcium (nobody is willing to disagree about calcium because it's politically correct to jump on the "calcium" bandwagon).
It would seem that loss of bone density is simply the adult form of rickets.