In order to study bone fracture in patients with osteoporosis, I need patient's exact muscle forces magnitude, location and direction (as FEA boundry conditions), while it is difficult to get such subjects to a MOCAP lab and get their data.
1. Is it possible to get a body-matched subject perform our tasks of interest (gait, stairs decent/accent, etc) and use their MOCAP data to run our simulation?
2. How reliable would be the calculated muscle forces in terms of magnitude and direction? how much the results would match the real patient?
3. Is there any other way to derive these patient's muscle forces? how accurate would be the results of these alternative methods?
Best regards
Yunus.
Is it possible to use someone else's MOCAP data?
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Yunus Rezvanifar
- Posts: 39
- Joined: Wed Oct 16, 2019 1:06 pm
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Dimitar Stanev
- Posts: 1096
- Joined: Fri Jan 31, 2014 5:14 am
Re: Is it possible to use someone else's MOCAP data?
Hi Yunus,
1. Yes, it is possible. You can perform generic scaling using OpenSim and the static pose or create a personalized musculoskeletal model from MRI (NMSBuilder). The latter requires a lot of manual effort and more measurements (e.g., MRI). Once you perform the analysis in OpenSim, you can also extract muscle force and points of application for FEA (https://simtk.org/projects/force_direction).
2. You have at least two sources of error: 1) modeling errors (geometries, joint frames, muscle paths, etc), 2) muscle redundancy problem. Even if you have a perfect subject specific model to solve the first problem, you will not be 100% sure that the muscle forces estimated with static optimization or other methods match the forces of the actual subject. There are some methods that use EMG ([1], https://simtk.org/projects/ceinms/), but they are also hard to calibrate. For some specific tasks, these methods give a good estimate of muscle recruitment. I guess we cannot do much better here if experimental measurements do not advance.
3. OpenSim offers at least 3 approaches: static optimization, computed muscle controls, ceinms.
[1] https://www.sciencedirect.com/science/a ... via%3Dihub
1. Yes, it is possible. You can perform generic scaling using OpenSim and the static pose or create a personalized musculoskeletal model from MRI (NMSBuilder). The latter requires a lot of manual effort and more measurements (e.g., MRI). Once you perform the analysis in OpenSim, you can also extract muscle force and points of application for FEA (https://simtk.org/projects/force_direction).
2. You have at least two sources of error: 1) modeling errors (geometries, joint frames, muscle paths, etc), 2) muscle redundancy problem. Even if you have a perfect subject specific model to solve the first problem, you will not be 100% sure that the muscle forces estimated with static optimization or other methods match the forces of the actual subject. There are some methods that use EMG ([1], https://simtk.org/projects/ceinms/), but they are also hard to calibrate. For some specific tasks, these methods give a good estimate of muscle recruitment. I guess we cannot do much better here if experimental measurements do not advance.
3. OpenSim offers at least 3 approaches: static optimization, computed muscle controls, ceinms.
[1] https://www.sciencedirect.com/science/a ... via%3Dihub
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Yunus Rezvanifar
- Posts: 39
- Joined: Wed Oct 16, 2019 1:06 pm
Re: Is it possible to use someone else's MOCAP data?
Thank you Dimitar for your great reply.
Can we also address the "lack of MOCAP data problem" with motion files shared by the community?
I another words, consider our patient as Subject_A and we want to use Subject_B motion file to run Inverse dynamics tool for subject_A implementing these two files:
1. Subject_B generalized coordinates file (SubjectB_walk_IK.mot) produced by Inverse kinematic tool.
2. Subject_B ground reaction force file (SubjectB_walk_grf.xml) which is scaled to Subject_A body weight.
How much the results would be reliable?
Best regards
Yunus.
Can we also address the "lack of MOCAP data problem" with motion files shared by the community?
I another words, consider our patient as Subject_A and we want to use Subject_B motion file to run Inverse dynamics tool for subject_A implementing these two files:
1. Subject_B generalized coordinates file (SubjectB_walk_IK.mot) produced by Inverse kinematic tool.
2. Subject_B ground reaction force file (SubjectB_walk_grf.xml) which is scaled to Subject_A body weight.
How much the results would be reliable?
Best regards
Yunus.
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Dimitar Stanev
- Posts: 1096
- Joined: Fri Jan 31, 2014 5:14 am
Re: Is it possible to use someone else's MOCAP data?
I do not think that using the GRF file of another subject with different weight and height would work. You can give it a try, but I expect that if you run ID and check the residuals at the pelvis they would be high. On the other hand, if you do not have a complete data set, you can use this approach, but your results might aggregate errors.