title: Comparison of three formal methods used to estimate the functional axis of rotation: an extensive in-vivo analysis performed on the knee joint.
abstract: Estimating the main axis of rotation (AoR) of a human joint represents an important issue in biomechanics. This study compared three formal methods used to estimate functional AoR, namely a cylindrical fitting method, a mean helical axis transformation, and a symmetrical axis approach. These methods were tested on 106 subjects undergoing navigated total knee arthroplasty. AoR orientation in 3D and in the frontal and coronal planes provided by each method was compared to the transepicondylar axis direction. Although all the methods resulted effective, significant differences were identified among them, relatively to the orientation in 3D and in the frontal plane projection. This was probably due to the presence of secondary rotations during the first degrees of knee flexion.
authors.affiliation: a Laboratorio di Biomeccanica e Innovazione Tecnologica, Istituto Ortopedico Rizzoli , Via di Barbiano 1/10, 40136 Bologna , Italy.|b Laboratorio di NanoBiotecnologie - NaBi, Istituto Ortopedico Rizzoli , Via di Barbiano 1/10, 40136 Bologna , Italy.|c The BioRobotics Institute, Scuola Superiore Sant'Anna , Pisa , Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Colle
authors.affiliation: a Laboratorio di Biomeccanica e Innovazione Tecnologica, Istituto Ortopedico Rizzoli , Via di Barbiano 1/10, 40136 Bologna , Italy.|b Laboratorio di NanoBiotecnologie - NaBi, Istituto Ortopedico Rizzoli , Via di Barbiano 1/10, 40136 Bologna , Italy.|d Dipartimento di Ingegneria dell'Informazione , Università degli Studi di Brescia , Via Branze 38, 25123 Brescia , Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Lopomo
authors.affiliation: a Laboratorio di Biomeccanica e Innovazione Tecnologica, Istituto Ortopedico Rizzoli , Via di Barbiano 1/10, 40136 Bologna , Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Visani
authors.affiliation: a Laboratorio di Biomeccanica e Innovazione Tecnologica, Istituto Ortopedico Rizzoli , Via di Barbiano 1/10, 40136 Bologna , Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Zaffagnini
authors.affiliation: a Laboratorio di Biomeccanica e Innovazione Tecnologica, Istituto Ortopedico Rizzoli , Via di Barbiano 1/10, 40136 Bologna , Italy.
authors.forename: Maurilio
authors.initials: M
authors.lastname: Marcacci
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D006801:Humans; D007719:Knee Joint / Q000502:physiology* / Q000601:surgery; D008875:Middle Aged; D012189:Retrospective Studies; D012399:Rotation
keywords: cylindrical fitting method; functional axis; knee kinematics; mean helical axis; navigated TKA; symmetrical axis approach