title: 3-D attitude representation of human joints: a standardization proposal.
abstract: In view of the singularities, asymmetries and other adverse properties of existing, three-dimensional definitions for joint and segment angles, the present paper proposes a new convention for unambiguous and easily interpretable, 3-D joint angles, based on the concept of the attitude 'vector' as derived from Euler's theorem. The suggested standard can be easily explained to non-mathematically trained clinicians, is readily implemented in software, and can be simply related to classical Cardanic/Eulerian angles. For 'planar' rotations about a coordinate system's axes, the proposed convention coincides with the Cardanic convention. The attitude vector dispenses with the 'gimbal-lock' and non-orthogonality disadvantages of Cardanic/Eulerian conventions; therefore, its components have better metrical properties, and they are less sensitive to measurement errors and to coordinate system uncertainties than Cardanic/Eulerian angles. A sensitivity analysis and a physical interpretation of the proposed standard are given, and some experimental results that demonstrate its advantages.
authors: University of Nijmegen, The Netherlands.
authors: H J
authors: HJ
authors: Woltring
mesh_terms: D000054:Acceleration; D000465:Algorithms; D005684:Gait / Q000502:physiology; D006801:Humans; D007596:Joints / Q000033:anatomy & histology / Q000502:physiology*; D007719:Knee Joint / Q000033:anatomy & histology / Q000502:physiology; D008954:Models, Biological; D009068:Movement; D016059:Range of Motion, Articular / Q000502:physiology; D012015:Reference Standards; D012399:Rotation; D012680:Sensitivity and Specificity