Mirroring right arm to the left on scapulothoracic model

[Arthur Matta]

Hello,

As a brief context, I'm developing an upper body model to record four movements: arm flexion, abduction and rotation, and shoulder elevation.

The arms' movements are fine, but the shoulder elevation reports incorrect orientation values for the coordinates. When elevating the shoulder, I expect the orientation to be positive for up and negative for down. I've separated the clavicle from the scapula to analyze them individually. The clavicles are working correctly, but the scapulas are not, reporting on the right side positive for up and negative for down, but for the left side, it's negative for up and positive for down.

I've already tried changing the translation of the Z-axis, the X and Y-axis orientation offset, and the thoracic ellipsoid radii value, but the problem remains.

Besides the elevation incorrect orientation, the same problem can be seen in the scapulas' abduction and winging.

Any help would be appreciated!
Best Regards

[Ayman Habib]

Hi Arthur,

As far as I know there are no published shoulder models with both sides, so I'd go back to process of mirroring (as it can get tricky) and pose any questions you have on the process here on the user forum as I'm sure multiple groups have either done it or are working on it as well.

Best regards,
-Ayman

[Luís Miguel Matos]

But to mirror the scapula (movements and restrictions) to the left side, what parameters would you use or change to configure the left side?

Best Regards,
Luis Miguel da Rocha de Matos (Habilitation, PhD)
Invited Assistant Professor, Department of Information Systems
Minho University, Campus de Azurem, 4804-533 Guimaraes, Portugal
Researcher at AlGORITMI center: https://algoritmi.uminho.pt/user/luis-m ... -de-matos/
Website: https://lmm.dsi.uminho.pt/

[Arthur Matta]

Dear OpenSim community,

My team is still facing issues mirroring the right side to the left on the scapulotoracic model. When dealing with flexio and elevation movements, the coordinates show, for the left side, double the value of the right side and inverted sign, respectively, e.g., right shoulder flexion shows +8 degrees when extending the arms forward while left shoulder flexion reports +25 and right shoulder elevation shows +10 when shrugging while left shoulder elevation reports -10. For reference, it was expected that for the flexion, both arms reported +8 and, for elevation, +10. We triple checked the readings from our IMU sensors and they are correct, hence we concluded the error to be in the mirroring. I, thereby, ask for your support. Any pointers is appreciated.

Best Regards,
Arthur Matta