Dear AnyBody team,
I’m working with AMMR v1.0 to calculate spinal loads during different tasks. Up to now, I’ve supposed that lumbar joints proximal-distal force is the disk compression force and the two others are in sum the shear force, even in the flexed trunk.
Is the standing initial posture your criteria for the proximal-distal direction? Or it’s an instantaneous direction in coincidence with trunk posture?
In other word, Is the proximal-distal force exactly my deformed disk compression force or it is only a global direction which should be projected to the new coordinate of disk?
Yes, it is the compressive force, you do not need to recalculate. It follows the orientation of the first reference frame that was used for the construction of a particular joint with the assumption of instantaneous centre of rotation (ICR).
Thank you very much Pavel. So I will confidently use joints proximal-distal force as the compressive force, in any rotated trunk.
Forces are named with two joints, e.g. L5SacrumProximalDistalForce.
Which plane is the force exactly exerted/projected to? Is the plane in the mean inclination of the upper and lower vertebrae??
As I said the first ref. frame is used as the orientation - that makes it to be the lower endplate for each joint in the spine. (it is, of course, not a perfect plane, but the reference frame is somewhat normal to it).
Thank you Pavel. The central plane of disk is the located in the mean inclination of the upper and lower vertebrae, esp. in the critical L5S1 disk. So we have to project the forces to the central plane of the disk.
Thank you again,