A modal approach for the soft tissue artefact mathematical representation and compensation

Overview & Synopsis

Optimal bone pose and joint kinematics estimators, that use data provided by stereophotogrammetry, aim at compensating for soft tissue artefacts (STA). We suggest that they embed a mathematical representation of the STA that adequately approximates it and uses a sustainable number of parameters. To this purpose we propose to represent STAs with a modal approach using different STA definitions: individual marker displacements (MrkD), marker-cluster geometrical transformations (GT), or skin envelope shape variations (SV). Modes can be ranked and a number of them selected leading to different degrees of approximation of the STA reconstruction and, therefore, compensation. This study investigated how, for each STA definition, the selected number of modes, the resulting STA approximation and accuracy of joint kinematics estimates relate to find the most appropriate STA mathematical representation.