Analytical study of the effects of soft tissue artefacts on functional techniques to define axes of rotation

摘要: Abstract The accurate location of the main axes rotation (AoR) is a crucial step in many applications human movement analysis. There are different formal methods to determine direction and position AoR, whose performance varies across studies, depending on pose source errors. Most based minimizing squared differences between observed modelled marker positions or rigid motion parameters, implicitly assuming independent uncorrelated errors, but largest error usually results from soft tissue artefacts (STA), which do not have such statistical properties effectively cancelled out by methods. However, with adequate it possible assume that STA only account for small fraction obtain explicit formulas through differential analysis relate components resulting errors AoR parameters. In this paper derived three functional calibration techniques (Geometric Fitting, mean Finite Helical Axis, SARA), explain why each technique behaves differently others, propose strategies compensate those These were tested published data sit-to-stand activity, where true axis was defined using bi-planar fluoroscopy. All able estimate an less than 5°, whereas there 30–40 mm. Such could be reduced 17 mm equations use parameters (mean SARA) when translation component calculated markers nearest axis.