The International Shoulder Group (ISG) is a collaboration of mostly biomechanically oriented research groups, whose main interest is in the shoulder. The ISG has been a Technical Group of the International Society of Biomechanics since 1999. The ISG aims to enhance shoulder research by creating a platform for discussion and the exchange of information, software and data. The constitution of the ISG can be found here (pdf). [more]
latest gh estimation files added
I've added the latest versions of DirkJan's routines to the ISG software repository at:
http://isg.case.edu/repository/kinematics/
These are Matlab routines for various transformations and calculations related to kinematics, including the calculation of the GH instantaneous helical axis (iha_3d.m, afgnew3d.m, woltring3d.m).
Ed Chadwick.
estimation of GH
it is not as difficult as it seems. what you need to do is:
1. measure the positions of the humerus relative to the scapula and calculate the resulting orientation matrices and origins; These can be the anatomical or technical matrices; do this for motions in different directions i.e. around all axes;
2. calculate the linear velocity and angular velocity
3. estimate the IHA;
4 calculate the pivot point;
If you want, I can help you with the programs. They should be on the site, but I have to look where and whether these are still up-to-date.
There is a price, though.... proper referencing ;-)
DirkJan
Least Squares
I'm also working on this issue. Have you tried using a least squares method? It is simpler, but almost equally as effective. These two websites are a good resource. I have also found Halvorsen's bias compensated method to be effective.
http://www.kwon3d.com/theory/jkinem/jcent.html
http://www.kwon3d.com/theory/jkinem/helical.html
-Adam
Rotation centre references
We'll try. Could you be more specific about what your problem is? If you haven't already seen them, the following papers may be useful to you:
- Stokdijk, M., Nagels, J. & Rozing, P. M. (2000) The glenohumeral joint rotation centre in vivo. IN J Biomech, 33. 1629–1636.
- Veeger, H. E. (2000) The position of the rotation center of the glenohumeral joint. IN J Biomech, 33. 1711–1715.
Ed Chadwick.
Meskers in Pathology
When working with data from subjects where there is abnormal movement of the scapula due to deinnervation of several of the scapular stabilizers, it seems that the Meskers method is not accurately finding the GH rotation center. Specifically it seems to be placing the GH center inferiorly from what would be logical. We have tried the method on data from healthy subjects and have not gotten this result.
Mathew Yarossi
myarossi@kmrrec.org