2010 RWISO Journal - Roth Williams International Society of ...

to the flag table (Figure 25). The Axi-Path is not a collinear
system, and errors often occur when the clinician attempts
to determine the THA. If a recording system is not collinear
and rectilinear, the clinician is likely to mark the inaccurate
hinge points on the skin.
Figure 24 Nasion relator cannot
move along the horizontal part of the bow.
Figure 25 When the lower frame is placed, the
stylus may not be perpendicular to the flag table.
The following experiment can be used to determine the
magnitude of measurement error. The experiment is set up so
that the measurement shows the right condyle 5 mm forward
of its actual position. For purposes of illustration, the situation
is assumed to be noncollinear (Figure 26).
Figure 26 Supposition. Right condyle moved 5 mm forward.
The new hinge axis diverges from the original hinge axis
as it goes farther from the anatomic structure (Figure 27).
Figure 27 New hinge axis passing through
newly positioned condyle.
The right recording stylus is placed at the new hinge
point on the flag table (Figure 28).
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