AnteroPosteriorShearForce

Hi,

I'm currently working with AnyBody.8.0 (AMMR.v3.0.0 and AMMR.v3.0.1) and I'm encountering some unexpected results regarding shear forces in different lumbar discs. Specifically, I'm noticing a strange result with the AnteroPosterior Shear force.

To provide some context, I attempted to run simulations using the BVH_BoxLift\Subjects\S01\S01_T01\Main for both versions in MocapExamples. However, the results I obtained seemed unusual.

I've attached some screenshots for your reference. You'll notice that the range of forces for the L4L5AnteroPosteriorShearForce and L5SacrumAnteroPosteriorShearForce exhibits significant differences (1800 N vs 100 N). From my understanding, such a gap shouldn't exist for L4L5 and L5S1 anteroposterior shear forces. Upon reviewing other AMMR versions (which didn't account for the slope of the endplate), I couldn't identify such a discrepancy between L4L5AnteroPosteriorForce and L5SacrumAnteroPosteriorForce.

While I acknowledge that considering the endplate slope can affect the magnitude of shear forces in the latest AMMR version, the current disparity between these values appears peculiar. I'd greatly appreciate it if you could review my simulation setup to see if I've overlooked any errors. It's worth noting that I haven't made any modifications to the repository model.


Hi Mohamad,

My initial guess would be that it indeed receives a compressive component due to how CS were defined for those joints. You can, in principle, define your own force measuring objects that will recalculate forces in more relevant planes. We have classes called AnyForceMomentMeasure/AnyForceMomentMeasure2 that allow to recompute forces in a given ref. frame. Could you try creating more logical ref. frame and reevaluate this? I believe the picture should make more sense.

Please check our Ref. Manual and search the Forum for how to use AnyForceMomentMeasures.

Let us know if run into problems or results still don't make sense.

Kind regards,
Pavel

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