N°006 - July / August 2020
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Total hip arthroplasty planning : Limits of x-ray and contribution of the CT-scan
By Christophe Castelain in category UPDATE
Clinique ARAGO - 187 A Rue Raymond Losserand - 75014 PARIS
Since the time of Maurice Muller in the 1980s, total hip arthroplasty has been planned using the reference standard x-ray method. Image digitisation and CT have since been used to develop high-performance planning software. In a large number of pathologies, CT has outmatched x-ray with its millimetric precision and three-dimensional image display. After seven years using CT-based planning software and comparing it with standard x-ray, I was able to see the shortfalls of conventional x-ray more clearly.
X-ray planning uses a frontal pelvic x-ray, with strict quality criteria: fixed plate-beam distance, standing position, knees in extension and feet in maximum internal rotation. In theory, this produces a frontal view of the hip with magnification identical to that of layers.
The image of the hip is projected onto the x-ray plate. Patient build, abnormal hip position and a tilted pelvis can distort the image projected. Such approximate planning, along with perioperative risks may lead to unequal length, or significant lateralisation, factors contributing to a poor functional result.
In an attempt to reduce these imprecisions, I chose to use CT image-based software as of 2008.
Its main advantage is that it is capable of providing sub-millimetric slices,...
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