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  #11  
Old 09-03-2016, 05:21 AM
kaison kaison is offline
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Default The angle of joint in lumbar

Dear pgalibarov

Thanks for your reply. I use motion capture system to get the coordinate of makers placed on the spinal process of L1,L5, T12 and T3. Then I drove mocap model with these markers. So I got the lumbar joint angle. However, the increasing angle from sacrum to thoracic segment maynot be reasonable no matter for health spine or pathological spine. The hypothesis that the stiffness increasing towards the sacrum dose make sense. But the angle of each joint doesnot make sense. How can I get reasonable lumbar joint angle through mocap model driven by the coordinate of markers I colleceted.

Thanks
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  #12  
Old 09-05-2016, 11:07 AM
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pgalibarov pgalibarov is offline
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Hello,

You have 3 options:
  1. To leave the current kinematic rhythm to drive the lumbar spine, and assume that the overall posture and muscular configuration does not differ much from the "real" one. Possibly think what kind of error is introduced by difference in IVAs, and how it affects your final measurements of interest.
  2. To replace the current rhythm with a new one, which would require you to find distribution of the intervertebral angles wrt. thoracopelvic angle yourself. An idea might be to take angle values from literature, measure your own curves from different posture x-rays, or contact an entity that measures such angles, e.g. a company: OrthoKinematics, EOS, etc.
  3. Use a special solver, Force Dependent Kinematics (FDK) solver, that find curvature based on the joint stiffnesses and ligament configuration, but it might be a more time/effort consuming simulation. Please check our manual for FDK.

Kind regards,
Pavel
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  #13  
Old 09-09-2016, 09:41 AM
kaison kaison is offline
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Default The angle of joint in lumbar

Dear pgalibarov

Thanks for your reply. Your suggestion is quite good. Then I tried to find the angle value from literature. But I found another question. I found one paper named “Which motion segments are required to sufficiently characterize the kinematic behavior of the trunk?” The angle value of T3 with respect to T12 was more than 20 degrees, that is to say, there were much motions among thoracic segments. But anybody models in AMMR all considered the thoracic segments as a rigid body. The result in that literature was similar with our experiment. I tried to add the 20 degrees to the T12L1 to represent the thoracic movement. It seemed a little large for one spinal unit. Is there any anybody model with detailed thoracic model? Or is there any other method to solve the problem of intersegmental motion of thoracic segments in anybody model?

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  #14  
Old 09-09-2016, 12:07 PM
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pgalibarov pgalibarov is offline
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Hello,

There is an existing model of the thoracic spine developed by ETH Zurich. Unfortunately this model will appear in one or another form in the AMMR later, but at the moment it is not available - possibly you could contact the authors directly for collaboration or to get the model.

Currently you cannot kinematically drive the thorax, but you could morph the thorax using our nonlinear scaling methods to take a certain shape, which might solve your case depending what your question of interest is.

Regards,
Pavel
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anykinmeasurelincomb, lumber, rhythm, rotation, shperical joints

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