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unknown user
08-09-1990, 11:30 PM
Minutes and comments on the informal workshop on 3-D Joint
and Segment Kinematics, held in Aarhus, Denmark, 8 July 90.


Dear Biomch-l reader,

Being a participant in the workshop, these are my comments about
the discussion held at the informal workshop organized by Dr. H.J.
Woltring in the margin of the VII ESB-meeting, in Aarhus.
As a CAMARC partner, I think that it is useful to give information
about this meeting to the largest scientific community and to
obtain feedback from other participants in the meeting and from
all other interested readers.

Sandro Fioretti

Department of Electronics and Automatica
University of Ancona
via Brecce Bianche
60131 Ancona - Italy
email: FIORETTI@ANVAX2.CINECA.IT

Report and Comments

An informal workshop under CAMARC has been held in Aarhus during the VII
Congress of the European Society of Biomechanics.
CAMARC (Computer Aided Movement Analysis in a Rehabilitation Context) is a
European project financed by the Advanced Informatics in Medicine (AIM)
Programme of the European Communities.

The workshop was organized by Dr.ir. H.J. Woltring (CAMARC partner) and
took place in a room of the Orthopaedic Hospital in Aarhus/DK.

About thirty persons were present coming from Europe and USA. In particular
Prof. Grood was the main participant after the long debate occurred with
dr. Woltring via the Biomch-L electronic mail discussion list. Almost one
half of the participants were physicians coming from public health
institutions.

Aim of the workshop was the discussion of some practical problems in
Movement Analysis. In particular:

- Joint angle definition (projected, cardanic, helical angles);
- Definition of Body-Segment Co-ordinate systems;
- Landmark cluster definitions per body segment;
- Anything else thought to be relevant.

>From the discussion it emerged that:

- It was debated, without final agreement, that a standard for the definition
of joint angle parameterisation can be valid for all joints. For some
joints (such as the shoulder complex) the helical representation could be
more efficient than the cardanic ones, while for other joints the opposite
could be true.

- It is recommended to pose the problem of the superiority of one angle
description with respect to another in the sense of its higher level of
regularity, globality and simmetry.

- There is the problem of the anatomical meaning of the angles obtained
with a particular parameterisation. This problem emerged very clearly
during the workshop because all non-technical participants ignored the
problems connected with the 3-D angle representations while they expected
to obtain from the various parameterisations the usual anatomical definition
of the joint angles.

- The above two points suggest that it could be useful to develop a
software tool mapping the results obtained with the most appropriate
angle parameterisation for a particular joint into an anatomical
conventional, easily understandable, representation of the same variables.

- These points suggest that it might be useful to think about how to
properly teach technically superior parameterisations with less physical
interpretability.

- The correct definition of the anatomical co-ordinate systems by external
marker positioning is unanimously recognized as a real problem for Movement
Analysis.

- The procudure proposed by dr. Woltring for a better alignment of the
technical axes with the anatomical ones was discussed with data obtained
at Ancona Movement Analysis Laboratory and relative to the analysis of
knee joint movement during locomotion. The correction of the cross-talks
among flexion with ab/adduction and with endo/exorotation constraining to
zero the latter two angles (obtained under the helical convention) in
correspondence of the maximum of knee flexion was not approved.
It was affirmed that the same procedure could be useful if correction is
performed in correspondence of 45 degrees of knee flexion during the
swing phase of gait.

[NB: The above procedure was merely proposed for demonstration; its main
purpose was to show how one m i g h t perform such corrections -- HJW]