Provide easy-to-use, extensible software for modeling, simulating, controlling, and analyzing the neuromusculoskeletal system.
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Mary K
- Posts: 37
- Joined: Mon Feb 24, 2014 9:15 am
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by Mary K » Thu Jul 17, 2014 4:54 pm
Hi there!
i want to create my own cruciate ligament but I cannot understand what this property exactly is:
Code: Select all
OpenSim_DECLARE_PROPERTY (pcsa_force, double,"force magnitude that scales the force-length curve")
(from the source code)
When I google "PCSA force" I find nothing, but only PCSA which is not a force but "physiological cross-sectional area" (from wikipedia).
Does anyone know more about the "pcsa_force"?
Thanks!
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jimmy d
- Posts: 1375
- Joined: Thu Oct 04, 2007 11:51 pm
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by jimmy d » Mon Jul 28, 2014 9:31 pm
Hi Maria,
The maximum isometric force for a muscle can be estimated from measured PCSA and a specific tension of 61 N/cm2. So even though PCSA is not a force, it is related to the force a muscle can produce.
Modeling ligaments are analogous to muscles without active components. Therefore PCSA can be used to scale the force-length curve of a ligament.
Cheers,
-James
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Mary K
- Posts: 37
- Joined: Mon Feb 24, 2014 9:15 am
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by Mary K » Thu Sep 04, 2014 11:01 am
Hi James,
thanks for responding!
Maybe you could answer my question here:
https://simtk.org/forums/viewtopic.php?f=91&t=5097
(it's seems that the function
bool Ligament::setMaxIsometricForce(double aMaxIsometricForce) sets the same value to the parameter 'pcsa_force':
set_pcsa_force(aMaxIsometricForce);. (Why?!)
The maximum isometric force for a muscle can be estimated from measured PCSA and a specific tension of 61 N/cm2.
When I study papers to find average measured parameters of ligaments (like length, strain etc) I don't ever find something like 'measured PCSA parameter'
Is there any possibility that the force-length curves found in the bibliography have already customized the results according to the pcsa_force parameter? So we can just set pcsa_force=1?
EDIT: In this paper there are measured values for cruciate ligaments' PCSA (mm^2).
http://www.sciencedirect.com/science/ar ... 094900280#
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jimmy d
- Posts: 1375
- Joined: Thu Oct 04, 2007 11:51 pm
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by jimmy d » Thu Sep 11, 2014 2:14 pm
Hi Maria,
That ligament code if pretty old and based off of muscle, hence the naming conventions. Even the idea of a max isometric force for a ligament is flawed. It appears this value just scales the related curves.
If you want to view the behavior, I would put ligaments on a model, adjust the parameters, and view the curves directly in the GUI.
The ligament class is on the development notes for a future release.
-james