Improving anterior deltoid activity in a musculoskeletal shoulder model – an analysis of the torque-feasible space at the sternoclavicular joint

Abstract

Modelling the shoulder's musculature is challenging given its mechanical and geometric complexity. The use of the ideal fibre model to represent a muscle's line of action cannot always faithfully represent the mechanical effect of each muscle, leading to considerable differences between model-estimated and in vivo measured muscle activity. While the musculotendon force coordination problem has been extensively analysed in terms of the cost function, only few works have investigated the existence and sensitivity of solutions to fibre topology. The goal of this paper is to present an analysis of the solution set using the concepts of torque-feasible space (TFS) and wrench-feasible space (WFS) from cable-driven robotics. A shoulder model is presented and a simple musculo -tendon force coordination problem is defined. The ideal fibre model for representing muscles is reviewed and the TFS and WFS are defined, leading to the necessary and sufficient conditions for the existence of a solution. The shoulder model's TFS is analysed to explain the lack of anterior deltoid (DLTa) activity. Based on the analysis, a modification of the model's muscle fibre geometry is proposed. The performance with and without the modification is assessed by solving the musculo -tendon force coordination problem for quasi-static abduction in the scapular plane. After the proposed modification, the DLTa reaches 20% of activation.

A simulation framework for humeral head translations

“…The associated results from the in vitro [17], in vivo [8,18,19,21], and numerical [10,[12][13][14] studies are also shown. present study, 6DOF present study, 3DOF Sins et al [12] Ingram et al [41] Bergman et al [43] Favre et al [14] Terrier et al [10] Quental et al [13] Nikooyan et al [5] Nikooyan et al [42] Figure 5: The GH joint contact force predicted by the present study and the associated results from numerical [5, 10, 12-14, 41, 42] and in vivo studies [43]. The results predicted by a similar GH joint model but with 3 DOF (ideal ball-and-socket) including the stability constraint is also shown.…”

Maximal isometric force exertion predicted by the force feasible set formalism: application to handbraking

“…Combined with the force amplitude obtained by data driven methods such as that proposed in (Wang et al 2010) both amplitude and direction can be assessed. However, the FFS allows to explain such direction, give more general information on the whole force capabilities and can be used for a wide range of applications including ergonomic indices for wheelchair propulsion (Hernandez et al 2018), for modulating the assistance of rehabilitation robots (Carmichael and Dikai 2013) or for improving the design of musculoskeletal models (Ingram et al 2016) to name a few.…”

“…The model of the FFS has identified limitations. Indeed, a stability constraint should be added to control the direction of joint force at the glenohumeral joint (Ingram et al 2016). More muscles should be considered especially those of the thorax.…”

Moment arms of the deltoid, infraspinatus and teres minor muscles for movements with high range of motion: A cadaveric study

“…abduct, flex and internally rotate the humerus at the same time), it is important to describe all three corresponding moment arms components. While the tendon excursion method may seem easy to implement, it can be improperly used, particularly in the case of multiple degrees of freedom and muscles spanning more than one joint 14 . The geometric method involves measurement of the perpendicular distance between the muscle's line of action and the joint centre of rotation 15 and computes the three moment arms components.…”