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Arno Grunendahl
01-27-2003, 08:37 PM
I thank everyone for the very usefull answers.
I'll keep you informed about my progress - it may take some time, though
;-)

Regrads

Arno Grunendahl

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Dear Arno,

In order to avoid relative displacement of marker points with respect to
the
underlying skeletal structures (due to skin movement), we use WLRT
imaging
techniques to capture the entire back surface in 3D, and active contour
techniques to trace the skeletal structures from surface data [1].
Thanks to
the fact that you have more information available - the entire back
surface
instead of marker points - a better estimation of vertebral rotation is
possible.

Dr. Hierholzer (Muenster, Germany) has published some articles on this
subject for static applications (e.g. scoliosis detection), and Diers
International (Wiesbaden, Germany) is commercializing the technique
(Formetric II). A European project (4D Bodyscan) has just started to
extend
the applicability of the technique to dynamic applications in general;
furthermore several Belgian labs are currently involved in a study to
measure whole body vibration with this technique (Vibracom,
www.vibracom.be).

Please contact me if you need more information.

Best Regards,
Bart Haex

[1] T. Huysmans, B. Haex, R. Van Audekercke, J. Vander Sloten, G. Van
der
Perre, R. Van Haute, J. Baeteman. 3D-postural analysis for the
evaluation of
spinal deformations during sleep. Ergonomic software tools in product
and
workplace design. A review of recent developments in human modeling and
other design aids. Edited by K. Landau, Verlag ERGON GmbH. Stuttgart,
2000,
ISBN 3-932160-11-8, 2000, pp 72-85.

-------------------------------------------
Dr. Bart Haex
Div. of Biomechanics and Engineering Design
Department of Mechanical Engineering
Faculty of Applied Sciences
Katholieke Universiteit Leuven
Celestijnenlaan 200 A
B-3001 Heverlee
Belgium
Tel: +32/16327057
Fax: +32/16327994
E-mail: bart.haex@mech.kuleuven.ac.be
------------------------------------------------------------------------

Arno,

It is very difficult to calculate vertebral vibration from skin mounted
markers or transducers. There are two problems: skin movement and
vertebral
rotation. You can use an impulse response method to calculate the local

skin movement and to then create a correction transfer function to apply
in
the time domain using convolution. This is described in Kitazaki and
Griffin, 1995 (J.Biomechanics). This works best for continuous
vibration
with a low crest factor; I would be concerned to use it with impulses.
(The
only data I know of that used impulses also used K-wires).

Vertebral rotation is very tough to compensate for without invasive
methods.

I have also published on this topic: the most relevant are
Mansfield NJ and Griffin MJ (2002) Effects of posture and vibration
magnitude on apparent mass and pelvis rotation during exposure to
whole-body
vertical vibration. Journal of Sound and Vibration 253(1) 93-107.

Mansfield NJ, Holmlund P, Lundström R (2001) Apparent mass and absorbed
power during exposure to whole-body vibration and repeated shocks.
Journal
of Sound and Vibration 248(3) 427-440.

and

Mansfield NJ and Griffin MJ (2000) Non-linearities in apparent mass and
transmissibility during exposure to whole-body vibration. Journal of
Biomechanics 33(8), 933-941.

I would be very interested to hear how you get on - if it works, then
new
possibilities would open up. Keep me informed!

I wish you success,

Neil.

____________________________
Dr Neil J Mansfield
Department of Human Sciences
Loughborough University
Loughborough LE11 3TU, U.K.
tel: +44 (0)1509 228483
fax: +44 (0)1509 223940
http://humsci.lboro.ac.uk/vibration
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Dear Arno,
I would suggest to try miniature accelerometers mounted on the
skin. Analog Devices have some very small ones.
A related problem was addressed by Kitazaki and Griffin, A data
correction method for surface measurement of vibration of the
human body. J. Biomechanics 28, 885-890 (1995).
Hope this helps,

************************************************** *****
At Hof
Institute of Human Movement Sciences &
Laboratory of Human Movement Analysis AZG
University of Groningen
A. Deusinglaan 1, room 321
postal address:
PO Box 196
NL-9700 AD GRONINGEN
THE NETHERLANDS
Tel: (31) 50 363 2645
Fax: (31) 50 363 3150
e-mail: a.l.hof@med.rug.nl
http://www.ppsw.rug.nl/~ibw/
************************************************** *******
------------------------------------------------------------------------

A number of models have attempted to calculate displacement and
orientation of vertebral angles using external markers. Some of the
more
advanced ones have attempted to account for skin distraction and
intervening
adipose tissue as well. You might be able to use the equations from
there,
provided their measures and markers are similar enough to yours. I
assume
you have some way to account for the inertial effects of motion on the
markers themselves?

Written in French but it's very detailed and gives everything you need
to
complete the calculations (including skin distraction)
Sicard, C. Modélisation géométrique de la colonne lombeire dans le plan

sagittal. 1-298. 1991. Université de Montréal. Unpublished
Dissertation

The paper resulting from the dissertation. Good overview but not enough

detail.
Sicard, C. and M. Gagnon. 1993. A geometric model of the lumbar spine in
the
sagittal plane. Spine 18:646-658

Gracovetsky also has a very good model which is detailed in this paper.
Gracovetsky, S., N. Newman, M. Pawlowsky, V. Lanzo, B. Davey, and L.
Robinson. 1995. A database for estimating normal spinal motion derived
from
noninvasive measurements. Spine 20:1036-1046.

Lee and Chen have a series of papers in which they discuss the
development
of their model using Asian subjects. Some of their papers may have the
equations you'd need.

Lee, Y. H. and Y. L. Chen. 2000. Regressionally determined vertebral
inclination angles of the lumbar spine in static lifts. Clinical
Biomechanics 15:672-677.

Lee, Y. H., W. K. Chiou, W. J. Chen, M. Y. Lee, and Y. T. Lin.
Predictive
model of intersegmental mobility of lumbar spine in the sagittal plane
from
skin markers. Clinical Biomechanics 10[8], 413-420. 1995.

Chen, Y. L. 1999. Geometric measurements of the lumbar spine in Chinese
men
during trunk flexion. Spine 24:666-669.

Chen, Y. L. 2000. Predicting the vertebral inclination of the lumbar
spine.
Ergonomics 43:744-751.

Let me know if there is anything more I can do to help,
Riley

Riley Splittstoesser, MS AEP
Department of Environment, Health & Safety
212 Finley Golf Course Rd., CB #1650
Chapel Hill, NC 27517-4440
ergonomics@unc.edu
Phone: (919) 843-4642 Fax: (919) 962-0227 (EST)
http://ehs.unc.edu
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--
The king said sail, but the wind said no.

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