Introduction
Templating is the method by which a surgeon calculates the correct-sized
prosthesis from a pre- operative radiograph of the pelvis using a series
of transparent templates. This helps surgeons to recreate the normal anatomical
relationship of the pelvis to the femur and restore the normal biomechanics
of the hip joint.
Recently, specialist software (e.g. Orthoview,
Traumacad)
has allowed this process to be performed on picture archiving and communications
system (PACS). The measurement software contained in these programs is
extremely precise. However, if the initial calculation of magnification
is incorrect all subsequent measurements made will be inaccurate.
The development of X-CalibR
While the literature describes various methods, they all involved putting
a radio 
translucent
object in the x-ray beam to create an object of known size at the height
of the anatomical region of interest.
Because of the increasing incidence of obesity, scaling devices placed
on the outside of the hips are often missed from the field of view. This
problem has been solved by placing the calibration device between the
patient’s legs (eg Hipscaler).
This is unpopular with patients and radiographers as it raises concern
about hygiene, placement of the device causes embarrassment and time is
added to the procedure.
We therefore developed a method which completely avoids placing a radiopague
scaling object on the image.
