PDA

View Full Version : Angular representation of the shoulder joint



Wolf, Sebastian
07-04-2005, 07:53 PM
Dear Readers,
There have been numerous discussions in literature and also in the list about angular representation of the glenohumeral joint. How to deal with gimbal locks and how to describe joint motion and joint orientation.

For the analysis of typical everyday movements and the determination of joint range of motion a maybe "unconventional" convention came to my mind. (I know, it either does not work or it is not new... ;-)

My question is simple: Is the following convention new?

__________________________________________________ ______

Generalize the (clinical) projection of angles such that they describe an opening angle relative to a (clinical) plane or axis i.e:

1) Abduction: Opening angle to the transverse plane (or better: angle to the vertical axis)
This idea is not quite new since it is done similar in the spherical coordinate representation.
Unfortunately one has to give up the separation between abduction and adduction

2) Anteversion: Opening angle to the frontal plane
This convention I have not seen yet. It allows the separation of ante- and retroversion.

3) (if needed) Circumduction: Opening angle to the sagital plane (helps dividing ab-/adduction)
__________________________________________________ ______

To my understanding, this convention does not run into a gimbal lock.

In principle this convention would be feasible for the hip joint as well:
1a) Abduction: Opening angle to the sagital plane
In this case abduction and adduction can be separated.

2a) Flexion: Opening angle to the transverse plane (or vertical axis)
In principle, flexion then could not be separated from extension which probably is not well accepted in a clinical context.
However, since the hip joint (unlike the shoulder joint) typically does not allow abduction of 90 and more, one can work around the gimbal lock and separate ad hoc with the third plane:
Flexion: knee joint center is in front of the frontal plane
Extension: knee joint center is behind the frontal plane

The third DOF int/external rotation is definitely more complex and needs a separate discussion.

I would be happy about comments.

Sebastian

Dr. Sebastian Wolf
Manager GaitLab
Dept. of Orthopedic Surgery
University of Heidelberg
sebastian.wolf@ok.uni-hd.de
____________________________