Gail,
there are a large number of image analysis systems available. Some are user
friendly and some are not. Some are easy to use and many have a long
learning curve.
Whichever system you select you should at a minimum  ask the following
1.  Will this be used strictly for analysis of bone? If so then there area
limited number of measurements that may need to be made and some programs
available that require a short training period. Most of the systems are
designed to provide a wide range of measurements and this often complicates
their operation as you have to go through several steps to get to where you
need to be.
2.    Will this be cost effective for you? If you are carrying out
measurements at irregular intervals,  then errors will tend to creep into
your measurements. In this case it may be best to explore another lab doing
this for you.
3.    Will there be one operator or several?  If several then standards and
calibration need to be made for each operator to determine the level of
errors that can occur.
4.    Who will do the training?  If the company that sells you the program
is doing this then how long and frequent is the training, how much will it
cost. Will the company charge you for technical help calls?
5.    Probably the most important is the tissue preparation as far as
determining the errors that are introduced . As long as you can produce
uniformly stained sections of the same thickness and can have a set of
positive and negative controls this is usually OK.

I have a handout dealing with some of the errors. If you are interested let
me know and I will mail to you.
Barry