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View Full Version : Re: Locating Tibialis Anterior tendon's action line using MRI



asolimene53
05-08-2008, 03:16 AM
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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