Is it possible to change your bone structure naturally?!

Is it possible to change your bone structure naturally?

I've been reading up on some things, and I've started to wonder: Is it possible to change your bone structure at any time in life?
Can adolescents change bone structure?
What does calcium do to overall structure?
Can people get wider shoulders, less bow-legged, etc?

Please cite resources or supporting evidence. I'll only selected a referencing answer as best.

1 month ago
Okay, I might pick an answer without a cited source. Some of the answers so far have been really good factually, but haven't cited any resources.

Bones are actually not as hard as people realize and they can be made to grow or reshape into positions that are considered abnormal. it is primarily done by doing things like binding, restricting growth by confinement, and bracing. there is a web site that gives information about this
http://anthro.palomar.edu/adapt/adapt_1....
most restructure or shaping is done by confining in order to get wider shoulders etc surgical implants are required. bow legs can be corrected with braces..
Calcium is what gives the bones strength and prevents them from becoming brittle. It is possible to change the bone structure or shape without surgery only when the bones are still primarily cartilage and ossification has not ceased.