title: Comparative assessment of knee joint models used in multi-body kinematics optimisation for soft tissue artefact compensation.
abstract: Estimating joint kinematics from skin-marker trajectories recorded using stereophotogrammetry is complicated by soft tissue artefact (STA), an inexorable source of error. One solution is to use a bone pose estimator based on multi-body kinematics optimisation (MKO) embedding joint constraints to compensate for STA. However, there is some debate over the effectiveness of this method. The present study aimed to quantitatively assess the degree of agreement between reference (i.e., artefact-free) knee joint kinematics and the same kinematics estimated using MKO embedding six different knee joint models. The following motor tasks were assessed: level walking, hopping, cutting, running, sit-to-stand, and step-up. Reference knee kinematics was taken from pin-marker or biplane fluoroscopic data acquired concurrently with skin-marker data, made available by the respective authors. For each motor task, Bland-Altman analysis revealed that the performance of MKO varied according to the joint model used, with a wide discrepancy in results across degrees of freedom (DoFs), models and motor tasks (with a bias between -10.2° and 13.2° and between -10.2mm and 7.2mm, and with a confidence interval up to ±14.8° and ±11.1mm, for rotation and displacement, respectively). It can be concluded that, while MKO might occasionally improve kinematics estimation, as implemented to date it does not represent a reliable solution to the STA issue.
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon 1, IFSTTAR, UMR_T9406, LBMC, F69622 Lyon, France; Università degli Studi di Roma - Foro Italico, Department of Movement, Human, and Health Sciences, Rome, Italy; Interuniversity Centre of Bioengineering of the Human Neuromusculoskeletal System, Università degli Studi di Roma "Foro Italico", Rome, Italy.
authors.forename: Vincent
authors.initials: V
authors.lastname: Richard
authors.affiliation: Università degli Studi di Roma - Foro Italico, Department of Movement, Human, and Health Sciences, Rome, Italy; Interuniversity Centre of Bioengineering of the Human Neuromusculoskeletal System, Università degli Studi di Roma "Foro Italico", Rome, Italy.
authors.forename: Aurelio
authors.initials: A
authors.lastname: Cappozzo
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon 1, IFSTTAR, UMR_T9406, LBMC, F69622 Lyon, France; Interuniversity Centre of Bioengineering of the Human Neuromusculoskeletal System, Università degli Studi di Roma "Foro Italico", Rome, Italy. Electronic address: raphael.dumas@ifsttar.fr.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Dumas
mesh_terms: D000328:Adult; D016477:Artifacts; D001696:Biomechanical Phenomena; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D009068:Movement / Q000502:physiology*; D012399:Rotation; D055815:Young Adult
keywords: Degree of agreement; Human locomotion; Kinematic constraints; Knee joint; Multi-body kinematics optimisation; Soft tissue artefact