Abdominal Pressure becomes zero at 40degree flexion

Hello,all

I encounter one problem when I try to simulate 40 degree flexion. I set an 40 degree flexion to drive facetjointSpine Model. However the abdominal force becomes zero at the end of the flexion. I am curious that this is true in reality or this is the limitation of the model? I test two different spine rhythm. Anybody give all almost zero force at the end of simulation.

Cheers,

Amin

Amin,

Value of almost 200 is not so close to 0.
Please check values on the ordinate axis.

Regards,
Pavel

Hello Pavel,

1.I do check the value it(it is like 0.0004). My question is this trend correct or not? Or I make some mistakes?

2.My second question is the compressive at L4L5 level in both SpinePressureStandingFlexed Model(Validation Folder) and Standing Model(Example Folder) is not the same, there is an difference about 30N. Can you tell me what is the difference between them? What makes such a difference? I already compare the anthropometric parameters, and it is quite the same.

I would really appreciate you if you can answer my question one by one.
Thank you very much!

Cheers,

Amin

Amin,

  1. Your image did not support your words. Secondly, it should grow. You are doing something wrong. I just tried on a normal standing model example, on FacetJointModel - it increases. Just imagine yourself bending forward and what your abdominal muscles experience.

  2. Validation study has a different size human:

   #include "<ANYBODY_PATH_BODY>\Scaling\ScalingLengthMassFat.any" 
     Scaling = {
       #include "AnyManUniform.any"
     };

Regards,
Pavel

[QUOTE][QUOTE][QUOTE]
[/QUOTE][/QUOTE][/QUOTE]Hello Pavel,

Thank you very much for the quick reply.

  1. The image aims to show you the trend of pressure. Like you said, the abdominal pressure should grow in the flexion process, which is also my expectation. I double check my model again. The basic model I use is SpineFixationWithFDK, I do two things, The first thing is to remove FDK, That is to say I use default Spine Rhythm. The second thing I modify the stiffness of the ligaments. I check there is huge difference between ligaments on and off. When the ligament on, the abdominal pressure is exactly increasing with time. However, when the ligament on the abdominal pressure is decreasing to zero. I attach this two results for review. I am confused about why this phenomenon appears? Since this test give me abdominal pressure, I think the program is correct.

  2. OK, I just check the anthropometric parameters before I ask the question. Now I understand that these two models use a different scaling methods. scalingstandard ethod is used in FacetJointModel and scalingLengthMassFat method is used in validation model. Is this correct?

Thank you very much. Hope my description is clear enough.

Best regards,

Amin

Hello Pavel,

Thank you for your quick reply.

The first problem is solved. However, I still have some problem about question 2.

  1. I compare two models with Validated Model. Now, we just focus on Validated standing model and SpineFixationWithFDK model. I check the code in SpineFixationWithFDKon Model, the scaling is the same which is attached as following. Both of them use LengthMassFat method. The body weight is 70 kg and height is 1.68. These parameters are all the same. Can you explain more clearly which size is different?
    #define BM_SCALING CONST_SCALING_LENGTHMASSFAT
    #path BM_SCALING_ANTHRO_FILE “Model/AnyManUniform.any”

If I am wrong please feel free to tell me.

Cheers,

Amin

Because I can not see the title for the images. I want to give some explanations. The first image is the result when the ligament is off and flexion forward 50 degree. The second image is the result when the ligament is on and flexion forward 50 degree. Because abdominal pressure is not always zero. I thought the reason is not about the script.

Thank you!

Amin

Hi Amin,

The models are quite different in terms of components and configuration. When I change posture and other parameters to be similar - i get same range loads (400 vs 450). The difference that I observe comes from not having legs in the SpineFixationWithFDK example. For example, psoas major muscles activate a little different. Hence, the difference in the loads.

If configurations were perfectly identical - you would get same results.

Kind regards,
Pavel

Hello Pavel,

Than you very much. I acquired the same number as you did. Your help is much appreciated.
Another question is that when I find the compressive force at L4L5 in both SpinePressureStanding(~450) and SpinePressureStandingFlex(~760). However, the result normalized to standing posture is 168%. Which seems not match the validation on Website, which is around 250%. Can you confirm this?

http://wiki.anyscript.org/index.php/Validation_examples

Thank you very much!

Cheers,

Amin

Hi Amin,

They might be referring to the magnitudes, but not just compressive components. I would need to find actual descriptions of these numbers. It might also be that something has changed in the model.

Kind regards,
Pavel

Hi Pavel,

Can you confirm this? I see many paper refer to compressive force at L4L5 level rather than the magnitude.

Thank you very much!

Cheers,

Amin

Amin,

I have looked at the abstract where this picture came from - it does not actually specify, but i have some vague memories of seeing an Excel document with the calculation, where it was a magnitude. But I looked at the values again - and it will not matter much, the ratio will still be in the same range.

So something has changed, and I would need to investigate this in more detail. But unfortunately I cannot promise you a quick answer.

Kind regards,
Pavel

Hello Pavel,

Thank you for your reply. I see many people use this validation to validate their model. Maybe they just visually check these data. I guess that the position is not matched each other. Cause I measure the angle of the SpinePressureStandingFlex Model. The angle is around 30 degree. However, the same pressure from Wike has a 36 flexion for whole upper body. I am not rush about the answer. But if you find exact answer, please let me know.

Cheers,

Amin