Thanks for providing the links to the articles.  They were informative.
   They did a bone scan on me within the last year.  My hips were just
fine, the spine showed osteoporosis.  I've been postmenopause for quite
a few years and on Dilantin 14 years and calcium intake had been low for
many, many years.  The bone scan technician said weight bearing seems to
 help save the hips from bone loss (one advantage of being over-weight!).

A few years ago I read an article on some of these hip fractures
actually being due to blood clotting disorders (such as factor V Leiden
or activated protein C resistance).

It certainly wouldn't hurt for your father to see his neurologist
because his low drug level of AEDs might be contributing to some of his
problems. I've had more problems at times of more serious health
problems, the ones that have been associated with a prolonged elevated
temperature, but now that I think about it, maybe it was the body stress
and not the fever that produced a few breakthrough symptoms.

There are medications to help prevent bone loss (like Fosamax).
Apparently bone is being made by the body but the loss is greater than
what the body can remake.  Some of these drugs help balance/slow down
that gain/loss ratio a little better.

Barb