In order to study bone fracture in patients with osteoporosis, I need patient's exact muscle forces magnitude, location and direction (as FEM 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 multi-body dynamics simulation (using OpenSim software)?
2. How reliable would be the calculated muscle forces in terms of magnitude and direction?
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.
Muscle forces are difficult to estimate under the best of circumstances. A body-matched subject will not solve the problem since it is unlikely that muscle recruitment patterns and anatomical relationships will be identical. The best approach is to do a sensitivity analysis for the FEM: i.e., run the model with changes in the boundary conditions, altering these incrementally one at a time. This will give you an idea of how significantly errors in the boundary conditions influence the model. A good example of this is :
Ross CF, Patel BA, Slice DE, Strait DS, Dechow PC, Richmond BG, Spencer MA. Modeling masticatory muscle force in finite element analysis: sensitivity analysis using principal coordinates analysis. The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology 2005 Apr;283(2):288-99.
As far as I read, it's okay to get a body-matched volunteer do the tasks,
but you should consider differences between muscle attachment sites which may slightly differ force directions
and muscle's max force capacity which relies on muscle volumes.
Modifying Musculoskeletal model with respect to patient's MRI may do the trick.
Of course, level of accuracy needed depends on your research question.
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