# Spine modeling - Curvature of the spine TH12 to C1 and Joint Positions

Hello,

my name is Niclas from FH Aachen.

I have some questions regarding the modeling of the spine from TH 12
up to C1.

1.) In which way is the curvature of the lumbar spine modelled?
I mean not the spine movement, but the modeling of the curvature.

I’m not sure, if I should use the middle points of the vertebra bodies
for positioning or the positions of the posterior sides of the bodies
for the curvature.

2.) Where’ s the exact position of the spine coordinate system at the
sacrum between the lumbar spine and the promontorium at the sacrum? -
In the middle of the promontorium = middle of the S1 body?

2.) In which way are the positions of the joints between the lumbar
vertebrae calculated / chosen? Just in the middle-point of the discus
intervertebralis between two vertebrae?
In the thoracic spine and especially in the cervical spine the IAR’s
(instantaneous centers of rotation) are below the Discus position of a
joint unit.

Niclas

Hi Niclas

I am not sure if i understand your first question. The spine is
driven by a spine rhythm which automatically sets the rotations in
the joints of spine as a function of the rotations between thorax
and pelvis. It is possible to exclude this rhythm from the model
then you will have to drive the three rotations of each joint
manually. In this case you are free to choose how to drive the spine
you may use linear measures on the posterior points on the
vertebraes or middle points on the vertebraes or other ways. I think
i need a description of the model you intend to build to be able to
help better on this question.

The spine use one coordinate system for all the segments, you can
display this by typing

`````` AnyDrawRefFrame drw={ScaleXYZ={0.1,0.1,0.1};};
``````

in for example the pelvis segment, (brep/aalborg/spine/pelvisseg.any)

The coordinate system is located at the upper part of crista
sacralis median.

The joint rotation centers in the lumbar spine are found using the
reference Pearcy and Bogduk (1988)

Pearcy,M.J., Bogduk,N., Instantaneous axes of
rotation of the lumbar intervertebral joints, Spine,
13 (1988) 1033-1041.

You are right that the joint centers of the thoracic and cervical
spine is located below the discus. These joints are not part of the
model yet, the current spine model has only the lumbar joints. We
have just initiated a project focusing on the cervical part of the
spine, so this will at some point be part of the repository.

If you look at the previous webcast at
slide number 14 shows the joints centers of the lumbar spine in the

Please do not hesitate to write again if you have further questions.

Best regards
SÃ¸ren, AnyBody Support

— In anyscript@yahoogroups.com, “niclaswetzel” <niclas.wetzel@…>
wrote:
>
> Hello,
>
> my name is Niclas from FH Aachen.
>
> I have some questions regarding the modeling of the spine from TH
12
> up to C1.
>
> 1.) In which way is the curvature of the lumbar spine modelled?
> I mean not the spine movement, but the modeling of the
curvature.
>
> I’m not sure, if I should use the middle points of the vertebra
bodies
> for positioning or the positions of the posterior sides of the
bodies
> for the curvature.
>
> 2.) Where’ s the exact position of the spine coordinate system at
the
> sacrum between the lumbar spine and the promontorium at the
sacrum? -
> In the middle of the promontorium = middle of the S1 body?
>
> 2.) In which way are the positions of the joints between the lumbar
> vertebrae calculated / chosen? Just in the middle-point of the
discus
> intervertebralis between two vertebrae?
> In the thoracic spine and especially in the cervical spine the
IAR’s
> (instantaneous centers of rotation) are below the Discus position
of a
> joint unit.
>