Biomedical Engineering Reference
In-Depth Information
Figure 3.9.
JCS of the trapezo-metacarpal joint
Let us provide another example where the
recommendations can be discussed. The ISB recommends,
for all finger joints, sequence Z-X-Y [WU 05]. With regard to
the trapezo-metacarpal joint at the base of the thumb, this
choice is not the most appropriate. Indeed, this joint has two
degrees of freedom [CHE 11]: flexion/extension about axis
attached to the trapezium bone and abduction-adduction
about axis
attached to the first metacarpal. Also,
sequence Z-Y-X, giving priority to the joint mobility axes,
provides more consistent angles [CHE 09].
3.3. Joint translations or displacements
Although most studies focus on joint angles and neglect
translations, especially since there are currently few
in vivo
measurement systems that are accurate enough to
appropriately assess translations, the complete description of
joint movement requires this to be tackled. The publication
by Grood & Suntay, based on ISB recommendations for the
description of joint angles, also proposed a method for
determining “joint translations” applied to the knee
[GRO 83]. This description allows a clinical interpretation,
but corresponds, strictly speaking, to the displacement of a
