Modeling the circumduction mechanism of thumb metacarpal through muscle-tendons actuation using bond graph

The thumb has a very special role in the functioning of the human hand due to the presence of the trapeziometacarpal joint (TMCJ) at the base of thumb metacarpal. There is a distinctive motion characteristic of the metacarpal in which its head and base rotate in opposite directions during the circumduction. This paper aims to present the model of musculoskeletal actuation of the thumb metacarpal for understanding the generation of articulating surface at TMCJ and to emulate the role of the central nervous system (CNS) for the control of muscle-tendon excitation. The model is aimed to determine the extension and force patterns among the associated muscle-tendon units (MTUs).

Motion of the thumb metacarpal through muscle-tendon actuation has been modelled using bond graph approach. Bond graphs are labelled, directed graphs that present energy-based technique where power transactions between component subsystems are the basis of modeling. The model is simulated for the circumduction motion.

An articulating saddle surface profile is generated at the TMCJ which agrees with the available literature. The role of the CNS has been emulated through the concept of a virtual domain. The model is able to determine the extension and force patterns generated among the associated MTUs.

The model developed is useful in studying the thumb metacarpal TMCJ movement, forces, joint torque, extension and force patterns in the muscle-tendon units that develop during the tasks. It has been demonstrated that the bond graph approach can be fruitfully employed in the process of analysing the musculoskeletal actuation.