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tmgreiner58
05-08-2008, 03:42 AM
A few comments in response to my response on the tibialis anterior. I
think we are mostly in agreement, but perhaps talking past each other.


"1. The anatomical planes of reference are arbitrary.

2. The line of force or action of any muscle does / do not occur "along
an artificial, and arbitrary, geometry" - it occurs where it occurs AND
during the range of motion of the involved body segments the position of
the line of action of a muscle continuously changes."

This was my point exactly, although perhaps you say it better. The
anatomical planes are artificial and arbitrary and if you limit your
investigation to those planes you should not be surprised that muscle's
action line has an oblique orientation.

"4. I respectful disagree that the line of action need be in the
sagittal plane to obtain meaningful data. It is done mathematically."

I agree completely. This is a consequence that a muscle's force of
action "occurs where it occurs." That, is another way of saying that you
should not expect of find anatomical evidence of a muscular action line
if you limit your investigation to a single anatomical plane.
Investigations in three dimensions may eventually allow you to resolve
an action line to a particular plane, but before you can do that math
you need to know what the muscle does when it does something. Inasmuch
as Tibialis Anterior is a dorisflexor and an inverter (or perhaps
sometimes and everter) the line of action of its insertion tendon will
lie oblique to the sagittal plane. Therefore you cannot caputre the
muscle's action line if investigation is limited to that plane. This is,
effectively, the same thing as saying that for the "TA there are more
than one line of action."

Thomas M. Greiner, Ph.D.
Anatomist and Physical Anthropologist
Dept. of Health Professions
University of Wisconsin - La Crosse
1725 State Street
La Crosse, WI 54601 USA

-----Original Message-----
From: as572@columbia.edu [mailto:as572@columbia.edu]
Sent: Thursday, May 08, 2008 12:16 PM
To: BIOMCH-L@NIC.SURFNET.NL
Cc: Greiner Thomas
Subject: Re: [BIOMCH-L] Locating Tibialis Anterior tendon's action
lineusing MRI


Dr Greiner,

Four thoughts and observations ..

1. The anatomical planes of reference are arbitrary.

2. The line of force or action of any muscle does / do not occur "along
an artificial, and arbitrary, geometry" - it occurs where it occurs AND
during the range of motion of the involved body segments the position of
the line of action of a muscle continuously changes.

A long while ago - some anatomists differentiated "Pure" from "Compound"
motion.
Pure motion was supposed to occur within (parallel to) the three
anatomical planes. Compound motion was any movement that
simultaneous intersected two or more of the anatomical planes.
Fortunately this unwieldy descriptive method is no longer widely used.

a. To my knowledge there is no general agreement as to action of the
tibialis anterior muscle. In Lanz and Wachsmuth's anatomical atlas, the
tendon to the tibialis anterior lies on the axis of inversion and
eversion, if that is its true location, i.e. its moment arm relative
to this axis is zero. One can therefore conclude that in the
anatomical position the TA is neither, and functions as a dorsi-flexor.
This conclusion is perhaps most reasonable.

I don't recall the reference, but I remember learning that electrical
stimulation of the belly of the TA would produce inversion in @50% of
cases and in @50% eversion. It may be worth redoing this study.

3b. In the case of the TA it is realistic to consider the reversal of
muscle action during the range of motion of the foot at the ankle.
This could be associated with the recruitment of muscle force during
movement / locomotion.

4. I respectful disagree that the line of action need be in the sagittal
plane to obtain meaningful data. It is done mathematically.

For Dr. Miller -
Most likely, given the width of the tendon and the area of attachment of
the TA there are more than one line of action.

For Thomas -
FYI - I am also an anatomist and physical anthropologist

Cheers

Dr. Alfonso Solimene



Quoting Greiner Thomas :

>
> I believe the problem you are encountering is due to the fact that
> that action of tibialis anterior is oblique to the anatomical
> reference planes. You are forcing the measurement of muscle activity
> to occur along an artificial, and arbitrary, geometry.. Inasmuch as
> tibialis anterior is primarily a foot inverter, I doubt that you would

> ever be able to obtain realistic and meaningful measured values if
> your perspective is limited to the sagittal plane.
>
> Thomas M. Greiner, Ph.D.
> Anatomist and Physical Anthropologist
> Dept. of Health Professions
> University of Wisconsin - La Crosse
> 1725 State Street
> La Crosse, WI 54601 USA
>
> -----Original Message-----
> From: * Biomechanics and Movement Science listserver
> [mailto:BIOMCH-L@NIC.SURFNET.NL] On Behalf Of Stuart Miller
> Sent: Wednesday, May 07, 2008 9:10 AM
> To: BIOMCH-L@NIC.SURFNET.NL
> Subject: [BIOMCH-L] Locating Tibialis Anterior tendon's action line
> using MRI
>
> Hello all,
>
>
>
> My colleagues and I have recently started to calculate the moment arm
> of the tibialis anterior and Achilles tendon. The method we are using
> is the Reuleaux graphical analysis. The images of the ankle are
> collected using MRI techniques. The images are collected in the
sagittal plane.
> This technique has been described in Maganaris et al. (1999); Clinical

> Biomechanics 14 pp661-666.
>
>
>
> The problem we are experiencing is of locating the action line of the
> tibialis anterior. The tibialis anterior tendon crosses the sagittal
> plane, so only an oval cross-section can be seen. This does not appear

> enough to accurately locate the action line of the tendon.
>
>
>
> I am wondering if anyone has experienced this problem whilst using
> this technique, and if so, can suggest any solutions.
>
>
>
> The action line of the Achilles tendon is easy to see as it acts along

> the sagittal plane.
>
>
>
> I will forward a summary of the responses in a few weeks.
>
>
>
> Thank you in advance.
>
>
>
>
>
> Stuart C. Miller BSc. (Hons)
>
> Centre for Sports Medicine and Human Performance
>
> Brunel University
>
> London
>
> Middlesex
>
> UB8 3PH
>
>
>
>
>
>
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