Musculoskeletal lower limb models have been shown to be able to predict hip contact forces (HCFs) that are comparable to in vivo measurements obtained from instrumented prostheses. However, the muscle recruitment predicted by these models does not necessarily compare well to measured electromyographic (EMG) signals. In order to verify if it is possible to accurately estimate HCFs from muscle force patterns consistent with EMG measurements, a lower limb model based on a published anatomical dataset (Klein Horsman et al. 2007. Clin Biomech, 22. 239-247) has been implemented in the open source software OpenSim. A cycle-to-cycle hip joint validation was conducted against HCFs recorded during gait and stair climbing trials of four arthroplasty patients (Bergmann et al. 2001. J Biomech, 34, 859-871). Hip joint muscle tensions were estimated by minimizing a polynomial function of the muscle forces. The resulting muscle activation patterns obtained by assessing multiple powers of the objective function were compared against EMG profiles from the literature. Calculated HCFs denoted a tendency to monotonically increase their magnitude when raising the power of the objective function; the best estimation obtained from muscle forces consistent with experimental EMG profiles was found when a quadratic objective function was minimized (average overestimation at experimental peak frame: 10.1% for walking, 7.8% for stair climbing). The lower limb model can produce appropriate balanced sets of muscle forces and joint contact forces that can be used in a range of applications requiring accurate quantification of both.
The aim of this project is to provide a reliable model to estimate muscle and joint reaction forces related to daily life and sport tasks.
The London Lower Limb Model model is based on one of the most recent anatomical dataset published in the literature (Klein Horsman, 2007). All the data used in the model were originally collected on a single cadaver in order to ensure consistence between geometrical data, joint kinematics and muscle contraction parameters.
Compared to other models available in the literature the number of actuators representing every muscle was chosen through a mechanical criterion (Van der Helm and Veenbaas, 1991). The model includes 163 muscle actuators, representative of 38 muscles.
(Video background from OpenSim 3D World Objects Library, https://simtk.org/home/simgym).
A new version of the model is about to be released and will allow the study of complex full body kinematics including neck and upper extremities.
August 2014: Falsification of the lower limb modelAug 17, 2014
A falsification technique was recently applied to the London Lower Limb Model (LLLM) in order to assess if the musculoskeletal model was able to replicate the hip contact forces measured from instrumented prostheses for the same kinematics and kinetics.
Further work on validation of the London Lower Limb ModelOct 6, 2011
The paper “Prediction of hip contact forces and muscle activations during walking at different speeds” (authors Modenese L.
July 2011: ISB 2011Jul 25, 2011
Luca Modenese gave an oral presentation titled "A lower limb model validated through in vivo measured joint contact forces." at the 23rd Annual Congress of the International Society of Biomechanics in Brussels, Belgium (3-7 July 2011).
March 2011: Euromech Colloquium 511Mar 28, 2011
An oral presentation titled "Hip contact forces during gait and their sensitivity to muscle synergism." was given at the Euromech Colloquium 511: Biomechanics in Motion, New Frontiers of Multibody Techniques for Clinical Applications in Ponta Delgada, Portugal (9-12 March 2011).
The lower limb model described in the publication is available for download. This model can be used to estimate muscle and hip contact forces during daily living activities. Only static optimization simulations are possible at this stage of development.See all Downloads
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