ISB standards

I have a qustion regarding the coordinate systems that are set-up for
the model. You referenced earlier that the body model coordinate
system is (on the right) where x is medial/lateral, horizontal to the
ground, y is inferior/superior, vertical to the ground, and z is
anterior/posterior, horizontal to the ground
(http://www.fbw.vu.nl/research/Lijn_A4/shoulder/isg/proposal/protocol…).
The environment however, seems to be defined differently, with X and
Z interchanged. Looking at the wheelchair model, for example, the
Xaxle distance is the forward/backward dist from pelvis to axle, while
the Zaxle distance is half the width between wheels. Why is this?

Thanks,
Sarah

Hi Sarah

Each segment of the arm has it’s coordinate system defined following
the recomendations in

http://www.fbw.vu.nl/research/Lijn_A4/shoulder/isg/proposal/protocol.
html

The orientation of the surrounding environment however are
completely free to choose for the user.

Typically the segmental coordinate systems are setup using
bonylandmarks on the bones, whereas the environment around the human
in principle can have any desired orientation. Typically if you hook
the model up on measured data you will choose to have the
orientation of the coordinate system you are measuring in, for the
environment.

Best regards
AnyBody support

— In anyscript@yahoogroups.com, “Sarah R. Sullivan”
<sarsulli@e…> wrote:
>
> I have a qustion regarding the coordinate systems that are set-up
for
> the model. You referenced earlier that the body model coordinate
> system is (on the right) where x is medial/lateral, horizontal to
the
> ground, y is inferior/superior, vertical to the ground, and z is
> anterior/posterior, horizontal to the ground
>
(http://www.fbw.vu.nl/research/Lijn_A4/shoulder/isg/proposal/protocol
…).
> The environment however, seems to be defined differently, with X
and
> Z interchanged. Looking at the wheelchair model, for example, the
> Xaxle distance is the forward/backward dist from pelvis to axle,
while
> the Zaxle distance is half the width between wheels. Why is this?
>
> Thanks,
> Sarah
>

Hi Sarah and Anybody Support,

I followed the discussion about the coordinate systems and I am a
little bit confused about the ISB recommendation in the referenced
article.
To explain my interest in this topic I should say that we at the
biomech lab of the Charite in Berlin are also interested in contact
forces ( and moments) of the glenohumeral joint and we measure them
by a telemeterized shoulder implant ( more informations at
www.biomechanik.de)
In order to publish our findings in a widely accepted coordinate
system I was looking for recommendations and found an article in the
Journal of Biomechanics where the y-axis is vertical pointing up, z-
axis (right shoulder) is pointing horizontal lateral and x-axis is
pointing horizontal and forward.!?!
(ISB recommendation on definitions of joint coordinate systems of
various joints for the reporting of human joint motion—Part II:
shoulder,elbow,wrist and hand,J Biomechanics, Article in Press,
Accepted 27 May 2004)

Best Regards

Peter Westerhoff

— In anyscript@yahoogroups.com, “AnyBody Support” <support@a…>
wrote:
>
> Hi Sarah
>
> Each segment of the arm has it’s coordinate system defined
following
> the recomendations in
>
>
http://www.fbw.vu.nl/research/Lijn_A4/shoulder/isg/proposal/protocol.
> html
>
> The orientation of the surrounding environment however are
> completely free to choose for the user.
>
> Typically the segmental coordinate systems are setup using
> bonylandmarks on the bones, whereas the environment around the
human
> in principle can have any desired orientation. Typically if you
hook
> the model up on measured data you will choose to have the
> orientation of the coordinate system you are measuring in, for the
> environment.
>
> Best regards
> AnyBody support
>
> — In anyscript@yahoogroups.com, “Sarah R. Sullivan”
> <sarsulli@e…> wrote:
> >
> > I have a qustion regarding the coordinate systems that are set-up
> for
> > the model. You referenced earlier that the body model coordinate
> > system is (on the right) where x is medial/lateral, horizontal to
> the
> > ground, y is inferior/superior, vertical to the ground, and z is
> > anterior/posterior, horizontal to the ground
> >
>
(http://www.fbw.vu.nl/research/Lijn_A4/shoulder/isg/proposal/protocol
> …).
> > The environment however, seems to be defined differently, with X
> and
> > Z interchanged. Looking at the wheelchair model, for example, the
> > Xaxle distance is the forward/backward dist from pelvis to axle,
> while
> > the Zaxle distance is half the width between wheels. Why is this?
> >
> > Thanks,
> > Sarah
> >
>

Hi Peter

I have looked into the article you referred to. You are right that
the articles use different coordinate systems for some segments, but
most of them i think are the same. The coordinate system you
describe i guess is the thorax coordinate system and this one is
different in the two articles, you are right. This will not affect
the GH reactions in any way. The GH reactions are measured in the
scapula coordinate system, please see the file “Brep/Arm3D/Jnt.any”
where the GH joint is defined in the following way:

//Definition of GH joint
AnyKinRotational GHRot = {
AnyRefNode &scapula_gh = …Seg.Scapula.gh;
AnyRefNode &humerus_gh = …Seg.Humerus.gh;
Type = RotAxesAngles;
Axis1 = y;
Axis2 = z;
Axis3 = y;
};

Please notice that the scapula segment in listed first so the
reactions will be measured in the scapula coordinate system.

I have compared the two coordinate system for scapula in the two
articles, they are very similar except that the axis is switched
around in the following way, (correct me if I am wrong)

X axis in the model corresponds to Z in the new article
-Z axis in the model corresponds to X in the new article
Y axis is the same
Origin is the same

These changes in the orientation of the scapula coordinate system
will naturally have the same influence on the reaction forces.

You may also change the orientation of the gh node on scapula by
changing its ARel, to make it fit any desired orientation.

Best regards
AnyBody Support

> Hi Sarah and Anybody Support,
>
> I followed the discussion about the coordinate systems and I am a
> little bit confused about the ISB recommendation in the referenced
> article.
> To explain my interest in this topic I should say that we at the
> biomech lab of the Charite in Berlin are also interested in
contact
> forces ( and moments) of the glenohumeral joint and we measure
them
> by a telemeterized shoulder implant ( more informations at
> www.biomechanik.de)
> In order to publish our findings in a widely accepted coordinate
> system I was looking for recommendations and found an article in
the
> Journal of Biomechanics where the y-axis is vertical pointing up,
z-
> axis (right shoulder) is pointing horizontal lateral and x-axis is
> pointing horizontal and forward.!?!
> (ISB recommendation on definitions of joint coordinate systems of
> various joints for the reporting of human joint motion—Part II:
> shoulder,elbow,wrist and hand,J Biomechanics, Article in Press,
> Accepted 27 May 2004)
>
> Best Regards
>
> Peter Westerhoff
>
>
> — In anyscript@yahoogroups.com, “AnyBody Support” <support@a…>
> wrote:
> >
> > Hi Sarah
> >
> > Each segment of the arm has it’s coordinate system defined
> following
> > the recomendations in
> >
> >
>
http://www.fbw.vu.nl/research/Lijn_A4/shoulder/isg/proposal/protocol.
> > html
> >
> > The orientation of the surrounding environment however are
> > completely free to choose for the user.
> >
> > Typically the segmental coordinate systems are setup using
> > bonylandmarks on the bones, whereas the environment around the
> human
> > in principle can have any desired orientation. Typically if you
> hook
> > the model up on measured data you will choose to have the
> > orientation of the coordinate system you are measuring in, for
the
> > environment.
> >
> > Best regards
> > AnyBody support
> >
> > — In anyscript@yahoogroups.com, “Sarah R. Sullivan”
> > <sarsulli@e…> wrote:
> > >
> > > I have a qustion regarding the coordinate systems that are set-
up
> > for
> > > the model. You referenced earlier that the body model
coordinate
> > > system is (on the right) where x is medial/lateral, horizontal
to
> > the
> > > ground, y is inferior/superior, vertical to the ground, and z
is
> > > anterior/posterior, horizontal to the ground
> > >
> >
>
(http://www.fbw.vu.nl/research/Lijn_A4/shoulder/isg/proposal/protocol
> > …).
> > > The environment however, seems to be defined differently,
with X
> > and
> > > Z interchanged. Looking at the wheelchair model, for example,
the
> > > Xaxle distance is the forward/backward dist from pelvis to
axle,
> > while
> > > the Zaxle distance is half the width between wheels. Why is
this?
> > >
> > > Thanks,
> > > Sarah
> > >
> >
>