Surface-to-surface Contact model with knee ligaments

Seyyed Hamed Hosseini Nasab · Post by **Seyyed Hamed Hosseini Nasab** » Fri Feb 03, 2017 2:59 am

Dear All,

I am trying to include surface to surface contact at tibiofemoral joint and knee ligaments into the Rajagopal Opensim model as I thought it could improve joint reaction force predictions of the model. I have skin marker data, fluoroscopic_based kinematics, EMG and ground reaction forces. I tried the joint reaction force analysis in opensim but results are very far from the in-vivo loads measured by instrumented implants. So, I want to replace constraint functions of the knee joint with contact surfaces and knee ligaments. Now, I have the following questions:
1- With a 6 dof knee, a Hertzian contact model and ligaments, how does the inverse kinematics tool in opensim work? If this is possible to do in opensim, I can validate the output kinematics with fluoroscopic kinematics otherwise I should directly feed the fluoro kinematics to the static optimization tool.
2- If I directly feed the fluoro kinematics to the static optimization tool, then what will be the role of contact model? Is it possible to get contact forces, ligament forces an muscle forces simultaneously from static optimization?
Actually, I am confused about the role of contact model. As far as I know, it should guide the joint motion together with ligaments but I saw some articles that they used contact model with the constraint functions. Could somebody please clarify this for me and suggest the possibilities that I can effectively use the unique data set that I have to improve JRF predictions of the standard opensim models. I appreciate your kind consideration.

With kind regards,
Hamed

Ross Miller · Post by **Ross Miller** » Fri Feb 03, 2017 8:32 am

Hi Hamed,

Regarding your second question on simultaneous modeling, I'm not sure if that can be done exactly with the Static Opt tool in the OpenSim GUI (it is likely possible with some effort in the API), but the following papers that had similar goals might be helpful if you haven't seen them already:

https://www.ncbi.nlm.nih.gov/pubmed/24390129
https://www.ncbi.nlm.nih.gov/pubmed/24389997
https://www.ncbi.nlm.nih.gov/pubmed/19962703

Good luck,
Ross

Seyyed Hamed Hosseini Nasab · Post by **Seyyed Hamed Hosseini Nasab** » Mon Feb 06, 2017 5:25 am

Dear Ross,

Thanks for introducing the articles. I got a very good insight to the problem by reading them.

Regards,
Hamed

Surface-to-surface Contact model with knee ligaments

Surface-to-surface Contact model with knee ligaments

Re: Surface-to-surface Contact model with knee ligaments

Re: Surface-to-surface Contact model with knee ligaments