Model Of Human Lower Extremity Research Articles

A COMPUTATIONAL STUDY OF DIFFERENT ADDITIVE MANUFACTURING-BASED TOTAL ANKLE REPLACEMENT DEVICES USING THREE-DIMENSIONAL HUMAN LOWER EXTREMITY MODELS WITH VARIOUS ANKLE POSTURES

Total ankle replacement (TAR) surgery is one of the useful methods to treat ankle arthritis. Selective laser melting that is an additive manufacturing (AM) technique has made it possible to fabricate orthopedic implants. However, there are rare studies to analyze AM implants using finite element method. Thus, the purpose of this study was to investigate the effect of the various porous designs with three types of tibial shapes for five ankle postures using three-dimensional (3D) human lower extremity models. The variable-axis-mobile-bearing (VAMB) TAR models were developed in one solid TAR design and three porous TAR designs on the tibial and talar components. Additionally, three shape designs (curved, flat, and tilted) of the tibial component were also evaluated. Each TAR design was assembled on the human lower extremity model with standing, inversion, eversion, plantar flexion, and dorsiflexion ankle postures. The results showed that there was a minor effect among the solid and porous TAR designs on the implant stability, the bone stress, and the implant stress. However, those performances in the plantar flexion were significantly reduced compared to that in the other ankle postures. Although the porous TAR designs have a higher risk of implant failure and bone breakage, it may have better bone-implant bonding ability. This study could help engineers and surgeons to understand the design rationale and biomechanics of AM-based TAR devices.

Repositioning the Knee Joint in Human Body FE Models Using a Graphics-Based Technique

Objective: Human body finite element models (FE-HBMs) are available in standard occupant or pedestrian postures. There is a need to have FE-HBMs in the same posture as a crash victim or to be configured in varying postures. Developing FE models for all possible positions is not practically viable. The current work aims at obtaining a posture-specific human lower extremity model by reconfiguring an existing one. Methodology: A graphics-based technique was developed to reposition the lower extremity of an FE-HBM by specifying the flexion–extension angle. Elements of the model were segregated into rigid (bones) and deformable components (soft tissues). The bones were rotated about the flexion–extension axis followed by rotation about the longitudinal axis to capture the twisting of the tibia. The desired knee joint movement was thus achieved. Geometric heuristics were then used to reposition the skin. A mapping defined over the space between bones and the skin was used to regenerate the soft tissues. Mesh smoothing was then done to augment mesh quality. Results: The developed method permits control over the kinematics of the joint and maintains the initial mesh quality of the model. For some critical areas (in the joint vicinity) where element distortion is large, mesh smoothing is done to improve mesh quality. Conclusions: A method to reposition the knee joint of a human body FE model was developed. Repositions of a model from 9 degrees of flexion to 90 degrees of flexion in just a few seconds without subjective interventions was demonstrated. Because the mesh quality of the repositioned model was maintained to a predefined level (typically to the level of a well-made model in the initial configuration), the model was suitable for subsequent simulations.

Forward dynamics simulation of human body under tilting perturbations

Human body uses different strategies to maintain its stability and these strategies vary from fixed-foot strategies to strategies which foot is moved in order to increase the support base. Tilting movement of foot is one type of the perturbations usually is exposed to human body. In the presence of such perturbations human body must employ appropriate reactions to prevent threats like falling. But it is not clear that how human body maintains its stability by central nervous system (CNS). At present study it is tried that by presenting a musculoskeletal model of human lower extremity with four links, three degrees of freedom (DOF) and eight skeletal muscles, the level of muscle activations causes the maintenance of stability, be investigated. Using forward dynamics solution, leads to a more general problem, rather than inverse dynamics. Hence, forward dynamics solution by forward optimization has been used for solving this highly nonlinear problem. To this end, first the system’s equations of motion has been derived using lagrangian dynamics. Eight Hill-type muscles as actuators of the system were modeled. Because determination of muscle forces considering their number is an undetermined problem, optimization of an appropriate goal function should be practiced. For optimization problem, the characteristics of genetic algorithms as a method based on direct search, and the direct collocation method, has been profited. Also by considering requirements of problem, some constraints such as conservation of model stability are entered into optimization procedure. Finally to investigate validation of model, the results from optimization and experimental data are compared and good agreements are obtained.

Performance analysis of a bumper–pedestrian contact sensor system by using finite element models

A pedestrian contact sensor in the car bumper is a potential solution to trigger an active hood system. Because of the high level of temperature dependency for the bumper foam stiffness, the sensor output can be unstable at varying temperatures. A new contact sensor was, therefore, developed to provide a temperature-independent measurement for pedestrian impacts. This study analysed the performance of the bumper–pedestrian contact sensor system. First, a baseline finite element (FE) bumper model of a production car was developed and validated. On the basis of the baseline model, an improved bumper model was subsequently developed to meet the requirements of the lower leg form impact tests proposed by Working Group 17 of the European Enhanced Vehicle-safety Committee. Second, an FE human lower extremity model was developed. Using this model, the baseline and improved bumper models were further evaluated in terms of the predicted knee ligament raptures and long bone fractures. Finally, the new contact sensor was built into the improved bumper model. A performance study was then conducted to evaluate the sensor effectiveness. Consequently, a better diameter for the sensor tube was identified in terms of the temperature stability and mass sensitivity of the sensor output.

Motion Analysis of Human Lower Extremity Considering Voluntary Muscle Contraction

The studies of man-machine interface have been researched in many technical fields. This paper presents the way of building human models with considering voluntary muscle contraction. Firstly, methods for evaluating muscular properties during static and dynamic conditions are proposed, and rations of muscular activity of dynamic load to static load are introduced. Secondly, human lower extremity model with muscular system is built and simulated by using multi body dynamics analysis software. The muscular systems based on Hill's characteristic equation that generate the knee extension and flexion with muscular contraction with considering active state of muscle. Lastly, the validity of the model and the way of approach are discussed.

3H 随意筋収縮を考慮した人体下肢の運動解析に関する研究(シンポジウム : ヒューマン・ダイナミクス2001)

The studies of man-machine interfaces are researched in many technical fields. To create mathematical human model helps to grasp the human functions which can not be measured in living human body. In this study, the mathematical model of human lower extremity is built up as a part of research to evaluate the functions of human exercise. Muscles perform important roles in human exercise. Therefore the first, we focused on the isokinetic exercise for knee extension and flexion, and measure electromyograms of each muscle on femur and tibia to identify the agonist. The next, the human lower extremity model are built up by using multibody program which simulate the gross motion of systems of bodies connected by kinematical joints. In this multibody analysis, muscular systems which based on Hill's characteristic equation generate the knee extension and flexion with muscular contraction by considering voluntary muscle contraction, that is, active state of muscle. Finally, the validity of this human lower extremity model is discussed by comparing with experimental torque.

Modelling of occupant biomechanics with emphasis on the analysis of lower extremity injuries

This paper addresses the use of finite element method to the simulation of humans in an impact environment. An extensive literature survey reveals several rigid body dynamics models of the human and sub-components, however, relatively little work has been performed using finite elements. Difficulties remain in characterising the material properties of the associated biological materials because of non-linear, inhomogeneous, anisotropic, and rate dependent behaviour. Physical testing using cadavers remains the primary means for determining human impact response and for validating the models created. A method for creating human finite element models is presented which requires the model to be developed in a ground-up approach and in a componentwise manner. Each component has five levels of detail with level one being a collection of rigid segments connected by simple joints and level five consisting of a highly detailed model with proper material properties and injury mechanisms included. This method has been employed to create a level two human lower extremity model. The model consists of accurate geometric segments of the individual bones in the leg. Each segment is connected using joint definitions in LS-DYNA3D that contain the non-linear stiffness characteristics of the hip, knee, and ankle. The model was used to simulate the loading conditions of a 50% overlap frontal collision of two mid-sized cars with a closing speed of 112 km/hr (70 mph). A parametric study to determine the effects of muscle tensioning was performed for twenty-seven different joint loading cases. Results indicated that muscle tensioning greatly affected the kinematics of the leg during high speed impact events. Greater stiffness in the hip and knee directly resulted in a higher potential for injury in the ankle. In addition, higher levels of muscle activation in the ankle reduced injuries from the deceleration pulse of the impact, however, toepan intrusion still presented potential harm to the ankle. Language: en