Comparison of model-predicted and measured moment arms for the rotator cuff muscles

Abstract

Background-The ability of mathematical models of the shoulder to accurately replicate physiological muscle moment arms is unknown. The purpose of this study was to compare modelpredicted and experimentally measured moment arms for the rotator cuff muscles during arm elevation.

Numerical modelling of the shoulder for clinical applications

“…Here, the rigid body models provide anatomical data, specifically the muscle moment arms and lines of action, as input to a coupled muscle force estimation method. Such models have been shown to predict accurately muscle moment arms of the rotator cuff in comparison with experimentally measured values (Gatti et al 2007), supporting the use of rigid body models for calculation of moment arms, with the advantage that these can be easily computed for any position of the joint at any time, as opposed to those measured experimentally. In turn, the determined muscle forces may then be used to drive the rigid body kinematics in a forward dynamics approach.…”

“…For instance, the simulated reachable workspace of the arm can be validated against actual measurements of range of motions (Klopcar et al 2007). Rigid body models used for the quantification of moment arms can also be directly compared with in vivo or in vitro measurements (Garner & Pandy 2001;Gatti et al 2007). Finally, when combined with muscle force estimation, in vivo measurements of maximum isometric muscle torques exerted at the joint and/or the resultant kinematics can be used for comparison, although these only validate the global simulation quality and do not yield specific information on individual muscle forces (Garner & Pandy 2001).…”

A transformation method to estimate muscle attachments based on three bony landmarks

“…glenohumeral rotation center) and making possible the direct linkage with the ones proposed by the International Society of Biomechanics recommendation for the reporting of human joint motion (Wu et al, 2005). In this sense, and taking into consideration that one of our current concerns is to make a a Values that are not in interval of the TMi moment arms published in Gatti et al (2007). shoulder model scalable to different subjects' anthropometric specificities, the method here presented could contribute therefore for a less time-consuming experimental setup, because it would take as input parameters the landmarks proposed on the above-mentioned kinematic proposal.…”

“…In order to test whether our errors are low enough to provide accurate outcome data, variations in TMi muscle attachment locations were applied to an upper extremity model (Holzbaur et al, 2005) using OpenSim software (Delp et al, 2007). Twentytwo of the 24 resulting moment arms were seen to be inside the interval of the TMi moment arms found in the literature (Gatti et al, 2007). Taking into account that we are using only three landmarks per subject and given the moment arms results from the TMi muscle, we can consider the amplitudes of the RMSE obtained in this study to be satisfactory.…”

“…In the end, 12 combinations were obtained (please see Table 3 for further details). The moment arms results were then compared with other published data (Gatti et al, 2007). The overall mean error of 7 mm (scapula) and 11 mm (humerus) were added, separately, to each coordinate of the correspondent muscle attachment.…”