GH estimate

[ilariaparel]

Dear Davide,

I am facing with the estimation of GH procedure. In order to estimate GH I ask patients to perform little circumductions of the shoulder and oscillations in the sagittal plane with the elbow flexed at 90°. Patients usually circunduct and oscillate in the sagittal plane. As I said, movements are very limited. The maximum humerus elevation is 45°, both in flexion and abduction . The problem is that for a patient, the GH has been estimated 1 meter away from the body. Labeling was correct, I double checked 1000 times. Then I decided to substitute the GH file with a regular ab-adduction task and the GH estimation was fixed. Please note that the patient cannot complete a full elevation, she stopped at 90° (more or less), so the movement was still limited. Do you have any idea about this problem? Thankyou very much. Ilaria

[u0078867]

Hi Ilaria,

what we perform in our labs here is a shoulder circumduction (neutral elbow, but this has no effect on the computation), i.e. the hand describes a circle. since the algorithm by Gamage searches for the center of a sphere, the more this circle radius is big, the better the algorithm performs. So, reduced motions can influence the results. Does the ab-adduction only motion span a larger angle than the circumduction motion? I think that using ab-adduction only motions can be a workaround, but perhaps the antero-posterior position of the GH is not the best...

Davide

[ejaspers]

Hi Ilaria,

I agree with Davide, that you need a sufficiently large range of movement (ROM) for the circumduction, in order for the algorithm to work properly. In Pellenberg, we try to perform the circumduction movements below 90degrees, but do encourage the subjects to move within that full space. What I would suggest in case subjects/patients are unable to execute ample ROM, is to do this passively, i.e. the assessor moves the arm in circumduction movements within the desired ROM field (ensuring that there is no marker occlusion!).

Have you compared the output for the GHr dynamic calculation (for the case mentioned, so based on the ab-adduction movement) with the output for the static calculation of the GHr (based on the regression analysis algorithm)? In my experience, using only the ab-adduction will not offer the most accurate reconstruction of the rotation center.

Good luck! Ellen

[ilariaparel]

Hi Ellen and Davide,

thank you for the information. Actually, I chose the ab/adduction movement just because it was the only movement available. For the future, I will ask patients to perform big movements of circumduction. So, based on what you said Ellen, the request should be "perform shoulder circumductions as big as possible"? Here we also acquire patients with shoulder prosthesis. They won't be able to perform big circumductions because of mechanical constrictions. In that case I will probably be forced to use the geometrical algorithm..

Can I ask a favor? Could you provide a short description of the main characteristics of the protocols listed in the mainGUI? eg. which is the difference between "Right" and "Right_Pellenberg"?

Thank you! Ilaria

[ejaspers]

Hi Ilaria,

as big as possible, meaning covering both the sagittal, the scapular and the frontal plane. Movements can go up to max. 90 degrees (not higher), and I would collect a number of repetitions (e.g. 5-10).

You could always ask the patients with shoulder prosthesis to perform the circumduction, perhaps with a passive assist? If this fails, yes the regression analysis is the best alternative.

With respect to the protocols, I would have to have a look at it myself again. If I remember correctly, the main difference between both protocols relates to the hand and the definition of the movement cycles: "Right_Pellenberg" protocol includes hand and uses part of the movement cycle (i.e. from start till a task endpoint is achieved) and the "Right" protocol has no wrist calculations and uses the whole movement cycle (i.e. abduction and adduction movement). I will double check and get back to you on this one, ok?

Cheers Ellen

[ilariaparel]

Hi Ellen,

thank you very much for te description of the GH movement! About protocols, the most important information I need is which protocol apply the geometrical definition of GH and which apply the Gamage algorithm... Thank you again Ellen!

Bye Ilaria

[u0078867]

Differences between Right and Right_Pellenberg:

• Kinematics; the BodyModel file used (e.g. marker names)
• Segmentation: the method (e.g. events sequence) used

In your own custom protocol, if you go to Kinematics > Functional JC options ... > and then you set as empty all the columns, the geometrical method is used instead (see AnatCalc files)

Best, Davide