Hello Colin, thank you for your answer. Basically my purpose is to compute the loads acting on intervertebral discs during various movements. The lumbar spine model represents the discs as rigid, incompressible joints, while I'd like to have a more realistic representation, taking into account the d...

Hi, I am currently working with the Lumbar Spine model by Christophy. The vertebral bodies are connected by custom joints that only allow for flex-extension, lateral bending and axial rotation. My question is: is it possible to define the joints so that they represent the intervertebral discs, takin...

Hi James,

thank you, but I am trying to use an actuator, because with ligaments or pathsprings I have problems in obtaining reasonable results when performing the Joint Reaction Analysis.

Best,

Michele

Hi, I am trying to use the Millard equilibrium muscle as a passive element, in order to represent a ligament. I modified various parameters in the muscle curves but was never able to obtain a suitable behavior, I have too much difference between the force developed in a static pose and the force dev...

Hi,

I went through the Customized Actuator tutorial but I couldn't make it work.

Is there any kind of spring actuator that is possible to use in OpenSim?

Thank you,

Michele

Sorry, for some reason it wouldn't let me attach files

Hi, In your case you don't need to supply any external force except muscle forces. What do you mean? Did I do something wrong in my Joint Reaction Analysis set up? And I am having difficulties in following: are you saying that if I only move the columns with their own label I must expect differences...

Hi, originally I was working on a static pose, so there were no accelerations involved. Now I tried with a flexion motion and with various PCSA forces for the ligaments. When I change the value of PCSA I see, indeed, changing magnitudes in both Static Optimization forces and Joint Reactions, so it s...

Hi Jim, I confirm that ligaments are included in Static Optimization (and therefore in its output force file) but are not considered during Joint Reaction Analysis. I tried to manually change the force file output of Static Optimization (StaticOptimization_force.sto) that is given as input in Joint ...

Hello Jim, No, I did not use any reserve actuator. Thank you for the reference to your work with ligaments; I think, though, that the problem is that OpenSim does not categorize ligaments as actuators, and therefore does not recognize them in the Joint Reaction analysis. The use of passive muscles t...