Childhood stem cell treatment leads to thinner bones?

Stem cell treatment for younger kids and even teens are increasing every year, but certain precautions need to be considered as these procedures increase in number. One of them is the propensity of these kids to develop thinning bones and possible vertebrae problems.

Research from Finland concluded that almost 33% of kids who had undergone allogenic (non-patient) stem cell transplantation ended up with thinning bones and even "crushed" vertebrae. I'm not sure that "crushed" was the most appropriate term to be used, but hey -- it got my attention.

What causes this? This will be very interesting to follow as it develops, as the "bone thinning" was seen more at the hip area than at any other place in the body.