In order to fully address pathologies affecting the movement and gait, there must be an understanding of the causes and effects of musculoskeletal disorders. To model the mechanical behavior of joints, muscles and skeletal tissues, two methods of computational modeling have arisen. The first is musculoskeletal modeling in which mechanical principals are utilized for describing the motion of a body which is modeled as a system of rigid bodies. The second is the finite element (FE) method which utilizes mathematical modeling and solving of complex equations for analysis. These methods can help estimate stress and strain for areas of the body including those which may be impossible to asses in a traditional experimental manner. The combination of these two methods provides promise of an integrated approach which may help as a new clinical tool for healthcare providers.
An integrated approach of the two computational models has been used in past and recent research. One limitation identified is the computational cost due to the complex computations which can be impractical for gait analysis in clinical settings- some researchers are addressing this concern by optimizing methods for computation cost-effective approaches.
A group of researchers from the FLENI Institute for Neurological Research in Argentina used integrative biomechanical framework for analysis of gait. The study utilized a simplified pelvis model for a model convergence study for comparison of performance with other models and a model sensitivity study to assess the effect of varying material factors. The group acquired data using MRI imaging and a Gait Lab consisting of a SMART – DX motion capture system and surface EMG system from BTS Bioengineering as well as force plates. The motion capture system utilizes infrared cameras and reflective markers on anatomical landmarks, while the EMG system acquires data on muscle activation.
For the musculoskeletal modeling, the marker data was used to scale a standard rigid-body musculoskeletal model. Data from the force plates and markers were used for inverse kinematics and dynamics for the calculation of joint angles and moments. For the subject-specific finite element (FE) modeling, the baseline geometry was determined through the motion capture analysis. The analysis focused on the hip joint, assumed to be a perfect ball and socket joint. The musculoskeletal model was integrated with the specialized FE model method using geometric conditions. Specific boundary conditions were also applied for assessment of the stress-strain behavior. The convergence and mesh refinement were completed as well as the sensitivity study in which the model was run at varying values of material properties such as the cartilage shear modulus and bone elastic modulus.
It was found that the “outcomes of the musculoskeletal model simulations (input of the pelvis FE model as physiological boundary conditions) were consistence with previous works” which indicates the promise and feasibility of this integrated approach for future uses. The estimations from the FE model of a sliding joint approximation were tested against the output of a rigid musculoskeletal model and were found to produce similar predictions of the net joint force. It was also found that the variations of material properties did not lead to significant changes in the FE models. Additionally, maximum stress peak areas were identified near the sacroiliac and pubis symphysis joint. With the information from the computational models, researchers were also able to gain insights about the stresses on the joints during different phases of the gait cycle.
The integration of computation models as demonstrated in this study hold the potential to improve therapy for chronic diseases and surgical interventions for patients with affected gait and motor function. The findings from such computational studies is valuable in advancing fields such as motion analysis, biomechanics, orthopedics and prosthetics. A better understanding of the musculoskeletal system and study of the joint forces can integrate into a more holistic approach for healthcare providers and inform decisions for patient care.
This post was based on the following article, cited:
Ravera, E. P., Crespo, M. J., & Catalfamo Formento, P. A. (2018). A subject-specific integrative biomechanical framework of the pelvis for gait analysis. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 0954411918803125.