View Full Version : Use of plananr x-rays to calculate hip joint centre

Penny Hewart
03-14-2001, 08:15 PM

I am looking at methods to obtain a 3D position of the hip joint centre
relative to external markers placed on the ASIS and PSIS. This would seem to
be possible (in theory) by back projection from 2 planar X-rays if a
calibration object with 8 known points is included in both images.

What I have not been able to find out (I have searched the archives and the
web) are the realities of this method - specifically the level of errors.
Ideally I would like to know the marker positions to within 2mm - is this a
realistic aim?

An alternative method is to use MRI, again does anyone know the accuracy of
the 3D positions as calculated by MRI in the 3 planes (I assume this varies
with the machine model - but a rough idea would be very welcome).

I shall post a summary of replies, thank you in anticipation,

Penny Hewart
Clinical Engineer
Gait Lab, CRC

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