title: Evaluation of regression-based 3-D shoulder rhythms.
abstract: The movements of the humerus, the clavicle, and the scapula are not completely independent. The coupled pattern of movement of these bones is called the shoulder rhythm. To date, multiple studies have focused on providing regression-based 3-D shoulder rhythms, in which the orientations of the clavicle and the scapula are estimated by the orientation of the humerus. In this study, six existing regression-based shoulder rhythms were evaluated by an independent dataset in terms of their predictability. The datasets include the measured orientations of the humerus, the clavicle, and the scapula of 14 participants over 118 different upper arm postures. The predicted orientations of the clavicle and the scapula were derived from applying those regression-based shoulder rhythms to the humerus orientation. The results indicated that none of those regression-based shoulder rhythms provides consistently more accurate results than the others. For all the joint angles and all the shoulder rhythms, the RMSE are all greater than 5°. Among those shoulder rhythms, the scapula lateral/medial rotation has the strongest correlation between the predicted and the measured angles, while the other thoracoclavicular and thoracoscapular bone orientation angles only showed a weak to moderate correlation. Since the regression-based shoulder rhythm has been adopted for shoulder biomechanical models to estimate shoulder muscle activities and structure loads, there needs to be further investigation on how the predicted error from the shoulder rhythm affects the output of the biomechanical model.
authors.affiliation: Liberty Mutual Research Institute for Safety, 71 Frankland Road, Hopkinton, MA 01748, USA. Electronic address: Xu.Xu@libertymutual.com.
authors.forename: Xu
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of Kinesiology, University of Waterloo, 200 University Ave W, Waterloo, ON N2L 3G1, Canada.
authors.forename: Clark R
authors.initials: CR
authors.lastname: Dickerson
authors.affiliation: Safety & Health Assessment & Research for Prevention (SHARP) Program, Washington State Department of Labor and Industries, P.O. Box 44330, Olympia, WA 98504, USA.
authors.forename: Jia-Hua
authors.initials: JH
authors.lastname: Lin
authors.affiliation: Liberty Mutual Research Institute for Safety, 71 Frankland Road, Hopkinton, MA 01748, USA.
authors.forename: Raymond W
authors.initials: RW
authors.lastname: McGorry
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D002968:Clavicle / Q000000981:diagnostic imaging / Q000502:physiology; D005260:Female; D006801:Humans; D006811:Humerus / Q000000981:diagnostic imaging / Q000502:physiology; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D009068:Movement / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D012540:Scapula / Q000000981:diagnostic imaging / Q000502:physiology; D012782:Shoulder / Q000000981:diagnostic imaging* / Q000502:physiology*; D012785:Shoulder Joint / Q000000981:diagnostic imaging / Q000502:physiology
keywords: ISB recommendations; Shoulder kinematics; Thoracohumeral joint