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Adam Cutler
07-14-1999, 08:23 AM
Hello list members,

Below is a summary of the replies I received for my request for
information about
aluminium step wedges. Thankyou to all who took the time to contact me.
If anyone has further information that they could pass on, please let me
know,

Regards

Adam Cutler
Orthopaedic Skills Unit
Dundee
Scotland

******* Original Message************

I am investigating the use of aluminium step wedges for determining bone

density from plain radiographs. I have found a number of papers from
researchers that use this method but would like more information to
clarify the technique and explain how the wedges are callibrated. Could
anyone give me the benefit of their knowledge or theoretical/practical
references? Also, does anyone know of or use other techniques for
determining bone density from plain radiographs?

***********************************

Dear colleague,
you will find enclosed a quick references list concerning the quality
control of x-ray film in bone density evaluation.

>From literature it seems that the indication for aluminum step wedges is

positive whenever soft tissue presence is moderate (hand, mandible).

This is not always true for orthopaedics (hip, spine) and "although the
aluminum stepwedge did prove helpful in measuring comparability in
serial
roentgenograms, it could not be actually used to compensate for slight
differences in roentgenographic techniques" (Engh et al. Clin Orthp
1993,
292, pp177-190)

The most relevant aspect to be improved is the overall x-ray technique.
In
my experience the best repeatability in quantitative densitometry from
hip
x-ray film is in the order of 10% also by the application of very strict

exposure protocol, aluminum step wedge and computerised elaboration
(i.e
equalisation).

If you need more precision (