Glenohumeral motion presents challenges for its accurate description across all available ranges of motion using conventional Euler/Cardan angle sequences without singularity. A comparison of the description of glenohumeral motion was made using the ISB recommended YX'. Y" sequence to the XZ'. Y" sequence. A direct in-vivo method was used for the analysis of dynamic concentric glenohumeral joint motion in the scapular plane. An electromagnetic tracking system collected data from ten healthy individuals while raising their arm. There were differences in the description of angular position data between the two different sequences. The YX'. Y" sequence described the humerus to be in a more anteriorly rotated and externally rotated position compared to XZ'. Y" sequence, especially, at lower elevation angles. The description of motion between increments using XZ'. Y" sequence displacement decomposition was comparable to helical angles in magnitude and direction for the study of arm elevation in the scapular plane. The description of the direction or path of motion of the plane of elevation using YX'. Y" angle decomposition would be contrary to that obtained using helical angles. We recommend that this alternate sequence (XZ'. Y") should be considered for describing glenohumeral motion.
Bibliographical noteFunding Information:
This study was funded by NIH Grant no. K01HD042491 from the National Institute of Child Health and Human Development. The content is solely the responsibility of the authors and does not necessarily represent the views of the National Institute of Child Health and Human Development or the National Institutes of Health. The authors would like to thank Cort J. Cieminksi, Ph.D., PT, ATC, CSCS; Daniel R Hassett, PT; Fred Wentorf, Ph.D.; Ed Gonda; Michael McGinnitty and Kelly Kyle, for their assistance with completing various aspects of data collection and analysis for this project.
- Euler/Cardan angles
- Gimbal lock
- Helical angles