A three-dimensional finite-element model of gluteus medius muscle incorporating inverse-dynamics-based optimization for simulation of non-uniform muscle contraction

Non-uniform contraction exists in many skeletal muscles and plays an important role in the function of the musculoskeletal system. Particularly in the gluteus medius (GM) muscle, its three subdivisions appear activated differently while performing various motion tasks. However, the non-uniform contractile mechanism of GM is poorly understood. In this study, a three-dimensional finite element (FE) model of GM was developed. Non-uniform contraction patterns of the three subdivisions of GM during abduction, internal and external rotation were simulated through an inverse-dynamics-based optimization approach. A set of sensitivity studies were also undertaken to evaluate the influence of parameters including the cost function of optimization and dimension of GM subdivisions on the predicted non-uniform contraction and biomechanics of the muscle. Contraction across GM was found to be highly non-uniform during various motions. The whole GM was activated during abduction, whereas only the anterior and posterior subdivisions were primarily involved in internal and external rotation, respectively. The active contractile stress in a subdivision during abduction was increased if its proportion in GM was expanded. The cost functions of minimizing the sum of active contractile stresses squared/cubed provide similar qualitative predictions of the trend of results. This approach provides the methodological basis to enable simulation of non-uniform muscle contraction using 3D musculoskeletal models. (C) 2020 IPEM. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study found that contraction in the gluteus medius muscle is highly non-uniform during abduction, internal and external rotation, with the entire muscle being activated during abduction while only specific subdivisions are primarily involved in internal and external rotation. The active contractile stress in a subdivision during abduction was found to increase if its proportion in the muscle was expanded. Cost functions of minimizing the sum of active contractile stresses squared/cubed provide similar qualitative predictions of trends in results.