title: Decrease of the electrical potentials measured on the surface of the knee and produced by cartilage compression during successive loading cycles.
abstract: Electroarthrography (EAG) is a new technique for measuring electrical potentials appearing on the knee surface during loading that reflects cartilage quality and joint contact force. Our objective was to investigate the evolution of EAG signals during successive loading cycles. The study was conducted on 20 standing subjects who shifted their body weight to achieve knee loading. Their EAG signals were recorded during 10 successive loading cycles, and during a subsequent sequence of 10 cycles recorded after a 15min exercise period. Multiple linear regression models estimated the electro-mechanical ratio (EMR) interpreting the ability of cartilage to generate a certain potential for a given ground reaction force by taking into account this force and the center of pressure displacements during unipedal stance. The results showed that the EMR values slowly decreased with successive cycles: during the initial sequence, the correlation coefficients between EMR values and sequence numbers were significant at 3 of the 4 electrode sites (p<0.05); for the post-exercise sequence, the EMR values still decreased and were significantly lower than during the initial sequence (p<0.001). The reduction of EMR values could arise from muscle activity and habituation of the stretch reflex, and also from the time dependent electromechanical properties of cartilage. In conclusion, refraining from physical activity before the EAG measurements is important to improve measurement repeatability because of the EMR decrease. The electromechanical model confirmed the role of EAG as a natural sensor of the changes in the knee contact force and also improved EAG measurement accuracy.
authors.affiliation: Institut de génie biomédical, Polytechnique Montréal, CP 6079 succ. Centre-ville, Montréal, Québec, Canada H3C 3A7.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Biomomentum inc., Laval, Québec, Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Garon
authors.affiliation: Biomomentum inc., Laval, Québec, Canada.
authors.forename: Éric
authors.initials: É
authors.lastname: Quenneville
authors.affiliation: Institut de génie biomédical, Polytechnique Montréal, CP 6079 succ. Centre-ville, Montréal, Québec, Canada H3C 3A7.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Buschmann
authors.affiliation: Institut de génie biomédical, Polytechnique Montréal, CP 6079 succ. Centre-ville, Montréal, Québec, Canada H3C 3A7. Electronic address: pierre.savard@polymtl.ca.
authors.forename: Pierre
authors.initials: P
authors.lastname: Savard
mesh_terms: D000293:Adolescent; D000328:Adult; D002358:Cartilage, Articular / Q000502:physiology*; D055724:Electrophysiological Phenomena; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D011312:Pressure; D016474:Weight-Bearing / Q000502:physiology*; D055815:Young Adult
keywords: Cartilage; Electroarthrography; Knee joint; Modeling; Streaming potentials