Alternative Representation of the Shoulder Orientation Based on the Tilt-and-Torsion Angles

Abstract

The International Society of Biomechanics (ISB) has proposed standardized recommendations for recording human joint motion. The Euler angles—the orientation representation currently proposed by the ISB—have two drawbacks, namely, the issue of singularities (gimbal lock) and the difficulty to obtain clinical and interpretable orientation representation for compound movements. The orientation representation of the shoulder joint with the Euler angles is particularly challenging due to its broad range of motion. This paper proposes and evaluates an alternative orientation representation for shoulder movement based on the tilt-and-torsion representation, a method that aims at providing a more clinically interpretable solution for describing joint movements compared to the standard Euler angles. Three studies were performed to compare the different orientation representation methods. The first two studies consist in simulations of arm elevation in different planes. The third study is an experiment using inertial-measurement-units with one test subject performing shoulder elevation movements in different planes. The tilt-and-torsion representation is then compared with different Euler angle conventions. The results show that Euler angles are biased or clinically uninterpretable for compound movements. Conversely, tilt-and-torsion representation does not suffer from these limitations. Although not extensive, the experiments suggest that the tilt-and-torsion representation has the potential to better represent human movements and provide more clinically interpretable results than the Euler angles.

Accuracy study of the Oculus Touch v2 versus inertial sensor for a single-axis rotation simulating the elbow’s range of motion

“…The sequence ZXY can be intuitively interpreted as the individual Euler rotations. This means that the first Euler angle represents a flexion of the arm, the second represents an abduction of the arm, and the third represents an internal/external rotation of the arm (Campeau-Lecours et al 2020). These data are sent via UDP to replicate the movement virtually.…”

The impact of experimental pain on shoulder movement during an arm elevated reaching task in a virtual reality environment

“…Joint angles were then calculated relative to the orientation of the trunk and upper arm sensors. The tilt‐and‐torsion “TT‐Z” rotation sequence (similar to YZY) was also used to calculate Euler angles to obtain the arm elevation (second angle of TT‐Z and YZY; Campeau‐Lecours et al, 2020 ). The variable of interest was the mean total joint excursion for each joint (final angle – initial angle) during the reaching movements, calculated for each reached target.…”

Interpreting the tilt-and-torsion method to express shoulder joint kinematics

“…The tilt-and-torsion (TT) method addresses the double humeral rotation problem by representing the shoulder orientation as a sequence of only two rotations (Campeau-Lecours et al, 2020). While still using the same three angles (plane of elevation, elevation, rotation), the humerus is rotated from its reference position directly in the plane of elevation, as shown in Fig.…”

“…Recently, Campeau-Lecours et al (2020) introduced the Tilt-and-Torsion (TT) method. This method is an extension of the Euler YXY method, the latter being recommended by the International Society of Biomechanics (ISB) (Wu et al, 2005).…”

“…Although TT has been tested with a single participant performing a standardized task (Campeau-Lecours et al, 2020), it has not been tested with a cohort of participants performing functional tasks. Propelling a sports wheelchair is a good example of such a task.…”