title: Hip joint centre position estimation using a dual unscented Kalman filter for computer-assisted orthopaedic surgery.
abstract: In computer-assisted knee surgery, the accuracy of the localization of the femur centre of rotation relative to the hip-bone (hip joint centre) is affected by the unavoidable and untracked pelvic movements because only the femoral pose is acquired during passive pivoting manoeuvres. We present a dual unscented Kalman filter algorithm that allows the estimation of the hip joint centre also using as input the position of a pelvic reference point that can be acquired with a skin marker placed on the hip, without increasing the invasiveness of the surgical procedure. A comparative assessment of the algorithm was carried out using data provided by in vitro experiments mimicking in vivo surgical conditions. Soft tissue artefacts were simulated and superimposed onto the position of a pelvic landmark. Femoral pivoting made of a sequence of star-like quasi-planar movements followed by a circumduction was performed. The dual unscented Kalman filter method proved to be less sensitive to pelvic displacements, which were shown to be larger during the manoeuvres in which the femur was more adducted. Comparable accuracy between all the analysed methods resulted for hip joint centre displacements smaller than 1 mm (error: 2.2 ± [0.2; 0.3] mm, median ± [inter-quartile range 25%; inter-quartile range 75%]) and between 1 and 6 mm (error: 4.8 ± [0.5; 0.8] mm) during planar movements. When the hip joint centre displacement exceeded 6 mm, the dual unscented Kalman filter proved to be more accurate than the other methods by 30% during multi-planar movements (error: 5.2 ± [1.2; 1] mm).
authors.affiliation: Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy elisa.beretta@polimi.it.
authors.forename: Elisa
authors.initials: E
authors.lastname: Beretta
authors.affiliation: Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: De Momi
authors.affiliation: Department of Movement, Human and Health Sciences, Università degli Studi di Roma Foro Italico, Rome, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Camomilla
authors.affiliation: Department of Information Engineering, Political Sciences and Communication Sciences, Università degli Studi di Sassari, Sassari, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Cereatti
authors.affiliation: Department of Movement, Human and Health Sciences, Università degli Studi di Roma Foro Italico, Rome, Italy.
authors.forename: Aurelio
authors.initials: A
authors.lastname: Cappozzo
authors.affiliation: Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy.
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Ferrigno
mesh_terms: D000465:Algorithms; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D007717:Knee / Q000601:surgery*; D008954:Models, Biological; D025321:Surgery, Computer-Assisted / Q000379:methods*
keywords: Hip joint centre; computer-assisted orthopaedic surgery; soft tissue artefact; unscented Kalman filter