These are good questionsâ€¦â€¦
I have reviewed the data from the Dutch shoulder group again regarding the
deltoid muscle and i have found this page
here the PCSA reads out as 2460 as written in the model, and as you I have
not been able to find figures that would distribute this PSCA between the
individual segments either, there is one number for all. In the model I can
see that the PCSA is not distributed equally this distribution is an
estimation made in lack of data. The overall idea was to have more PCSA on
the middle part and then gradually reduce the PCSA towards both sides.
I think in order to determine the clinical heads of the deltoid muscle
elements the best you can do is to look at their geometrical location.
Normally when we compare the muscle activity from these muscles with EMG we
collect the muscle activity output from several elements.
You are right about the differences in the dataset for the constant strength
muscles and the three element hill muscles. This is due to lack of data in
the VU data set for the data needed by the three element muscles.
The origin and insertion points given for the VU data set are all given wrt.
a global coordinate system as I recall it. Then using the positions of the
bonylandmarks and the definition of the segments coordinate system given in
these global coordinates has been changed to local segment coordinates,
therefore it can be difficult to directly find the numbers in the model in
the dataset. That said the origin and insertation points of several of the
muscles has been modified for several reasons, normally in order to fit
moment arm measurements. In the model it will usually have a comment saying
//corrected if the nodes has been moved wrt. original data.
Regarding the number of muscle elements on clavicle and scapula I have
reviewed a few of he old papers such as :
F.C.T. van der Helm and R. Veenbaas
Modelling the mechanical efect of muscles with large attachment sites:
application to the shoulder mechanism
Journal of Biomechanics, vol. 24, no. 12, pp. 1151-1163, 1991
A finite element musculoskeletal model of the shoulder mechanism
Journal of Biomechanics, vol. 27, no. 5, pp. 551-569, 1994
These both list six deltoid elements for clavicle and scapula as in the
I may have overlooked some of your questions, so please ask again if you
SÃ¸ren, AnyBody Support
From: firstname.lastname@example.org [mailto:email@example.com] On Behalf
Sent: 07 February 2008 15:24
Subject: [AnyScript] Re: Deltoids
I have also been wondering about dividing the deltoid into the
clinical heads. I can easily see that the clavicular portion could be
considered the anterior deltoid. And, I initially thought that equally
dividing the scapular portion into 3 middle and posterior segments was
the way to go as well. However, I have been trying to look in the
Arm3D files to find some information relating information about the
muscles to that from the VU study (subject 2), from which I believe
these parameters came. I have not been able to match origin and
insertion data, nor the PCSA data for each individual deltoid segment
(I don’t know if this is on the webpage of the Dutch Shoulder Group).
However, when looking at Muscle-parameters-shoulder.any (which I
understand is only used with the 3 element muscle model), the PCSAs
are taken from Holzbaur et al; the total PCSA of portions 3 through 6
of the scapular portion match that reported Holzbaur et al (8.2 cm^2),
and sum of portions 1 and 2 is close to that of Holzbaur et al (1.9
cm^2). But when looking at Muscle-parameters-shoulder-simple.any,
these PCSAs are different than Holzbaur et al and I am not sure what
portions are what.
Could you help clarify where these parameters came from in order to
better define (less-objectively) the clinical heads of the deltoid?
Also, I have heard it said that this shoulder model in AnyBody is an
implementation of the Dutch model. But, I believe the Dutch model has
4 clavicular deltoid portions and 11 scapular deltoid portions. Could
you give some clarification on this as well?
Thanks a lot.
> The muscle named “deltoideus_scapular_part_1” is the most posterior of
> the deltoid muslce branches. So i think “deltoideus_scapular_part_1”
> to “deltoideus_scapular_part_3” should be considered the posterior part
> wheras “deltoideus_scapular_part_4” to “deltoideus_scapular_part_6” is
> the middle part.
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