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Jim Patton (usa/chicago)
01-13-1995, 06:17 AM
About a month ago we raised two questions regarding biomechanics
of the lumbosacral joint. We got surprisingly few responses,
perhaps due to our timing (the holidays). The origininal
questions as well as a summary of responses follows, but
WE WELCOME ANY ADDITIONAL RESPONSES RELATED TO OUR QUESTIONS.

Thanks to all that responded.
Hsin-I Chang, B.S.
Wynne Lee, Ph.D.
Jim Patton, M.S.
Aileen Russo, M.S.
Julie Steege, B.S.

Motor control and learning group
Programs in Physical Therapy and Biomedical Engineering
Northwestern University
Chicago, Illinois, USA

____________________ ORIGINAL QUESTIONS: ____________________

Recently, our group has been doing some dynamic modeling on the full
body motions, and are interested in simple mechanical models of the
lumbar/sacral joint. We have two main questions:

(1) We are looking for reasonable estimates of the moment arms of intra-
abdominal pressure acting about the L5/S1 joint. We are aware of a
reference in an article by Chaffin:

Chaffin (1975) "On the validity of biomechanical models
of the low back for weightlifting analysis," ASME
Proceedings, 75-WA-bio-1.

This is also cited in Chaffin and Andersson's book:

Chaffin and Andersson, Occupational Biomechanics,
Wiley, New York, 1991.

Are there any other approaches we can take in modeling intra-abdominal
pressure? We are particularly interested in subject-specific models
based on scaling schemes based on bony landmark measurements. We are
hoping to obtain a simple relation between TORSO ANGLE and the L5/S1
intra-abdominal pressure MOMENT ARM.

(2) We also are trying to find a subject-specific scaling scheme (based
on bony landmarks, hopefully) for the distance from the skin surface to
L5/S1 joint center of rotation. Is there a database or study out there
that relates to this estimate in some way? We are aware of the work of
McNeill et al:

McNeill, T, Warwick, D, Andersson, GBJ, Schultz (1980)
"Trunk Strengths in attempted flexion, extension and
lateral bending in healthy subjects with low back
disorders," Spine 5: 529-538

This study places the L5/S1 joint center 34% from posterior on the
anteroposterior diameter. Is there any other related information out
there?

As always, we will post a summary of responses. Thanks in advance,

Hsin-I Chang, B.S.
Wynne Lee, Ph.D.
Jim Patton, M.S.
Aileen Russo, M.S.
Julie Steege, B.S.
Motor control and learning group
Programs in Physical Therapy and Biomedical Engineering
Northwestern University
Chicago, Illinois, USA


____________________ RESPONSES: ____________________
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Dear James,

Here's a few essential reading references to get started with.
They themselves probably cite some more. But the list is by no means
exhaustive. Note that the first one (Morris et al) is considered the
classic in this field, and goes a long way to answer your question, I
think. More recent writers (eg Stu McGill) would contest the
quantitative details probably.

Ian Stokes
University of Vermont, Department of Orthopaedics and Rehabil.
Burlington, VT 05405-0084, USA
Phone: (+1) 802 656 2250 fax: (+1) 802 656 4247
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Morris JM Lucas DB Bresler MS:
The role of the trunk in stability of the spine.
J. Bone Joint Surg. (Am) 43(3): 327-351. 1961.

David GC:
Intra-abdominal pressure measurements and load capacities for
females
Ergonomics 28(1):345-358,1985

Davis PR:
The use of intra-abdominal pressure in evaluating stresses on the
lumbar
Spine 6(1):90-92,1981

Gracovetsky S; Farfan H; Helleur C:
The abdominal mechanism.
Spine 1985 May;10(4):317-24

Hemborg B; Moritz U; Lowing H:
Intra-abdominal pressure and trunk muscle activity during
lifting. IV. The causal factors of the intra-abdominal pressure
rise.
Scand J Rehabil Med 1985;17(1):25-38

Krag MH, Gilbertson L, Pope MH:
Intra-Abdominal and Intra-Thoracic Pressure Effects Upon Load
Bearing of the Spine
Proceedings of 31st Orthopaedic Research Society, p. 328, 1985

Mariaux P, Davis PR, Stubbs DA, Baty D:
Relation between intra-abdominal pressure and lumbar moments when
lifting weights in the erect posture
Ergonomics 27(8):883-894, 1984

McGill et al.:
The effect of an abdominal belt on trunk muscle activity and
intra-abdominal pressure during squat lifts.
Ergonomics, 33(2), 147-160 1990.

McGill SM
Electromyographic activity of the abdominal and low back
musculature during the generation of isometric and dynamic axial
trunk torque: implications for lumbar mechanics.
J-Orthop-Res. 1991 Jan; 9(1): 91-103

McGill SM:
Electromyographic Activity of the Abdominal and Low Back
Musculature During the Generation of Isometric and Dynamic Axial
Trunk Torque: Implications for Lumbar Mechanics
J. Ortho. Res. 9:91-103, 1991

McGill SM; Norman RW; Sharratt MT:
The effect of an abdominal belt on trunk muscle activity and
intra-abdominal pressure during squat lifts.
Ergonomics 1990 Feb;33(2):147-60.

Tesh KM; Dunn JS; Evans JH:
The abdominal muscles and vertebral stability.
Spine 1987 Jun;12(5):501-8


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You may wish to consult the following:

Snyder, Chaffin, and Schutz, "Link System of the Human Torso,"
AMRL-TR-71-88, Aerospace Medical Research Lab., Aerospace
Medical Division, Air Force Systems Command, Wright-Patterson
AFB, Ohio. 1970.

Reynolds, Snow, and Young (1981). Spatial Geometry of the
Human Pelvis. Report No. AAC-119-01-5. Protection and
Survival Lab., FAA, Oklahoma City, OK.

The latter is a study of cadaver pelvis/sacrum geometry. I've
used these data to obtain an estimate of S1 location wrt
palpable pelvis landmarks. Some assumptions regarding the
location of the L5/S1 joint center wrt S1 gives a functional
estimate of the joint location from body landmarks (I use ASIS
and PSIS, or ASIS and Pubic Symphysis if I don't have access
to the back of the pelvis, e.g., with a seated subject).
These data are likewise useful for obtaining hip joint center
location from pelvis landmarks.

********
Matt Reed
Sr. Research Associate
University of Michigan
Transportation Research Institute
matt@biosci.umtri.umich.edu
********

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James, We have worked on IAP for a number of years and have a couple of
references that you may be interested in. It is difficult to predict IAP
particularly in a variety of tasks(McGill and Sharratt, Clin. Biomech.
5:59-67 1990. Also: McGill and Norman, Ergonomics
30(11):1565-1588 1987. where we also provide moment arms and geometry etc).
As well we have just finished work thast is in the review process where
data suggests that
IAP increases the compressive strength of the spine- this is a new twist.
There is no doubt that people build up IAP on exertion but we have never
been able to prove that it unloads the spine of compressive loading.
Good Luck with your search and work,
Stu McGill


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Dear colleages

>This study places the L5/S1 joint center 34% from posterior on the
>anteroposterior diameter. Is there any other related information out
>there?

Once I found a paper which claimed a distance of 50 - 52 % from anterior on
the AP diameter. But unfortunately I don't remember the author. It dealt
mainly with moment arms of the trunk musculatur.
Good luck
Paul
******************************************
* Klein Paul Ph.D. *
* Institut for Physical Therapy and *
* Rehabilitation *
* Free University of Brussels *
* CP 168, Avenue P. Heger, 28 *
* 1050 Brussels, Belgium *
* *
* Phone 32-2-6502470 Fax: 32-2-6502473 *
* pklein@resulb.ulb.ac.be *
******************************************

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