About disc pressure

Main Forum
1

Hi all,

I read results from J. Rasmussen ea al. (2009), which compare computed compression forces with measurements of Wilke ea al.
Using existing model in the folder : Application>Validation>WilkeSpinalDiscPressure , I try calculating the reaction load on L4L5.
To calculate this, I go to
Main.Study.Output.Model.HumanModel.Trunk.JointsLumbar.L4L5Jnt.Constraints.Reaction.Fout

My results are expected to get same results as Rasmussen et al, but these are different in while.
The loads of StandingLiftFlexed and StandingLiftStrechedArms are especially different, StandingLiftStrechedArms is maximum!
My results are calculated as follows,

SpinePresureStanding
Fout [0] Fout [1] Fout [2]
45.6 451 -0.00602
SpinePresureStandingFlexed
Fout [0] Fout [1] Fout [2]
93.5 762 -0.00147
SpinePresureLyingOnBack
Fout [0] Fout [1] Fout [2]
2.51 97.7 -0.000222
SpinePresureSeatingRelaxed
Fout [0] Fout [1] Fout [2]
23.2 178 -0.0831
SpinePresureSeatingStraitNoSupport
Fout [0] Fout [1] Fout [2]
61 413 0.0563
SpinePresureStandingLiftFlexed
Fout [0] Fout [1] Fout [2]
272 2070 -0.0354
SpinePresureStandingLiftStretchedArms
Fout [0] Fout [1] Fout [2]
349 2550 -0.0181
SpinePresureStandingLiftClose
Fout [0] Fout [1] Fout [2]
141 1300 -0.0398

I don’t know why these results are different…

AnyBody version is 4.2, AMMR 1.2

Best regards, Omiya

2

Dear Omiya,

As far as I can see from your picture, the difference is mainly in the Standing Lift Flexed and Standing Lift Straight arm cases, which seem to provide reverse results from what we found in our paper. My best guess is that this might be due to small postural differences between the models. For instance, in the flexed position you can obtain the flexion by spine flexion, hip flexion or a combination of the two, and the model is probably rather sensitive to which combination you choose. Please try some different combinations of these and observe whether the model is sensitive to those.

Unfortunately the reference by Wilke, from which we have the experimental data, does not contain precise motion capture data that would allow us to recreate his postures exactly in our models.

Best regards,
John

3

Hi, John,

Thank you for reply.

I didn’t know how sensitive these models are, it seems very complicated.
To obtain close to the reference by Wilke, I try some different combination and observe!

Best regards, Omiya