title: Bone Pose Estimation in the Presence of Soft Tissue Artifact Using Triangular Cosserat Point Elements.
abstract: Accurate estimation of the position and orientation (pose) of a bone from a cluster of skin markers is limited mostly by the relative motion between the bone and the markers, which is known as the soft tissue artifact (STA). This work presents a method, based on continuum mechanics, to describe the kinematics of a cluster affected by STA. The cluster is characterized by triangular cosserat point elements (TCPEs) defined by all combinations of three markers. The effects of the STA on the TCPEs are quantified using three parameters describing the strain in each TCPE and the relative rotation and translation between TCPEs. The method was evaluated using previously collected ex vivo kinematic data. Femur pose was estimated from 12 skin markers on the thigh, while its reference pose was measured using bone pins. Analysis revealed that instantaneous subsets of TCPEs exist which estimate bone position and orientation more accurately than the Procrustes Superimposition applied to the cluster of all markers. It has been shown that some of these parameters correlate well with femur pose errors, which suggests that they can be used to select, at each instant, subsets of TCPEs leading an improved estimation of the underlying bone pose.
authors.affiliation: Department of Mechanical Engineering, Technion Israel Institute of Technology, 32000, Haifa, Israel. danas@technion.ac.il.
authors.forename: Dana
authors.identifier: http://orcid.org/0000-0003-3215-0401
authors.initials: D
authors.lastname: Solav
authors.affiliation: Department of Mechanical Engineering, Technion Israel Institute of Technology, 32000, Haifa, Israel.
authors.forename: M B
authors.initials: MB
authors.lastname: Rubin
authors.affiliation: POLCOMING Department, Information Engineering Unit, University of Sassari, 07100, Sassari, Italy.|Interuniversity Centre of Bioengineering of the Human Neuromusculoskeletal System, University of Rome "Foro Italico", 00135, Rome, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Cereatti
authors.affiliation: Department of Movement, Human and Health Sciences, University of Rome "Foro Italico", 00135, Rome, Italy.|Interuniversity Centre of Bioengineering of the Human Neuromusculoskeletal System, University of Rome "Foro Italico", 00135, Rome, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Camomilla
authors.affiliation: Department of Mechanical Engineering, Technion Israel Institute of Technology, 32000, Haifa, Israel.
authors.forename: Alon
authors.initials: A
authors.lastname: Wolf
mesh_terms: D016477:Artifacts; D001696:Biomechanical Phenomena; D005269:Femur / Q000502:physiology*; D006801:Humans; D035002:Lower Extremity / Q000502:physiology; D009068:Movement; D010780:Photogrammetry; D012399:Rotation; D012867:Skin
keywords: Bone pose estimation; Cosserat point theory; Marker cluster; Motion analysis; Soft tissue artifact; Soft tissue deformation; Stereophotogrammetry; Triangular cosserat point element