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Heinrich D.,University of Innsbruck | van den Bogert A.J.,Orchard Kinetics, Llc | van den Bogert A.J.,Cleveland State University | Nachbauer W.,University of Innsbruck
Scandinavian Journal of Medicine and Science in Sports | Year: 2014

Recent data highlight that competitive skiers face a high risk of injuries especially during off-balance jump landing maneuvers in downhill skiing. The purpose of the present study was to develop a musculo-skeletal modeling and simulation approach to investigate the cause-and-effect relationship between a perturbed landing position, i.e., joint angles and trunk orientation, and the peak force in the anterior cruciate ligament (ACL) during jump landing. A two-dimensional musculo-skeletal model was developed and a baseline simulation was obtained reproducing measurement data of a reference landing movement. Based on the baseline simulation, a series of perturbed landing simulations (n=1000) was generated. Multiple linear regression was performed to determine a relationship between peak ACL force and the perturbed landing posture. Increased backward lean, hip flexion, knee extension, and ankle dorsiflexion as well as an asymmetric position were related to higher peak ACL forces during jump landing. The orientation of the trunk of the skier was identified as the most important predictor accounting for 60% of the variance of the peak ACL force in the simulations. Teaching of tactical decisions and the inclusion of exercise regimens in ACL injury prevention programs to improve trunk control during landing motions in downhill skiing was concluded. © 2013 John Wiley & Sons A/S.

Van Den Bogert A.J.,Orchard Kinetics, Llc | Van Den Bogert A.J.,Case Western Reserve University | Blana D.,Case Western Reserve University | Blana D.,Aberystwyth University | Heinrich D.,University of Innsbruck
Procedia IUTAM | Year: 2011

The ordinary differential equations for musculoskeletal dynamics are often numerically stiff and highly nonlinear. Consequently, simulations require small time steps, and optimal control problems are slow to solve and have poor convergence. In this paper, we present an implicit formulation of musculoskeletal dynamics, which leads to new numerical methods for simulation and optimal control, with the expectation that we can mitigate some of these problems. A first order Rosenbrock method was developed for solving forward dynamic problems using the implicit formulation. It was used to perform real-time dynamic simulation of a complex shoulder arm system with extreme dynamic stiffness. Simulations had an RMS error of only 0.11 degrees in joint angles when running at real-time speed. For optimal control of musculoskeletal systems, a direct collocation method was developed for implicitly formulated models. The method was applied to predict gait with a prosthetic foot and ankle. Solutions were obtained in well under one hour of computation time and demonstrated how patients may adapt their gait to compensate for limitations of a specific prosthetic limb design. The optimal control method was also applied to a state estimation problem in sports biomechanics, where forces during skiing were estimated from noisy and incomplete kinematic data. Using a full musculoskeletal dynamics model for state estimation had the additional advantage that forward dynamic simulations, could be done with the same implicitly formulated model to simulate injuries and perturbation responses. While these methods are powerful and allow solution of previously intractable problems, there are still considerable numerical challenges, especially related to the convergence of gradient-based solvers. © 2011 Published by Elsevier Ltd.

Kotina R.,Honeywell | Zheng Q.,Gannon University | Van Den Bogert A.J.,Orchard Kinetics, Llc | Gao Z.,Cleveland State University
Proceedings of the American Control Conference | Year: 2011

A fundamental and open issue pertaining to human postural sway is how to deal with the uncertain, nonlinear and time-varying nature of human motor dynamics. To address the inherent limitations of the current methods, such as PID and model-based designs, a novel active disturbance rejection concept is introduced. In this new framework, the uncertainties, nonlinearities and changes in the dynamics of the plant are treated as disturbance to be rejected. A unique disturbance rejection observer is employed to estimate it and compensate for it in real time. It is shown that the resulting new controller yields excellent performance even with significant uncertainties in the plant dynamics. Furthermore, such design strategy requires very little prior knowledge of the plant. © 2011 AACC American Automatic Control Council.

Van Den Bogert A.J.,Cleveland State University | Van Den Bogert A.J.,Orchard Kinetics, Llc | Geijtenbeek T.,Motek Medical B.V. | Even-Zohar O.,Motek Medical B.V. | And 2 more authors.
Medical and Biological Engineering and Computing | Year: 2013

Mechanical analysis of movement plays an important role in clinical management of neurological and orthopedic conditions. There has been increasing interest in performing movement analysis in real-time, to provide immediate feedback to both therapist and patient. However, such work to date has been limited to single-joint kinematics and kinetics. Here we present a software system, named human body model (HBM), to compute joint kinematics and kinetics for a full body model with 44 degrees of freedom, in real-time, and to estimate length changes and forces in 300 muscle elements. HBM was used to analyze lower extremity function during gait in 12 able-bodied subjects. Processing speed exceeded 120 samples per second on standard PC hardware. Joint angles and moments were consistent within the group, and consistent with other studies in the literature. Estimated muscle force patterns were consistent among subjects and agreed qualitatively with electromyography, to the extent that can be expected from a biomechanical model. The real-time analysis was integrated into the D-Flow system for development of custom real-time feedback applications and into the gait real-time analysis interactive lab system for gait analysis and gait retraining. © 2013 The Author(s).

Ackermann M.,State University of Maringa | Van den Bogert A.J.,Orchard Kinetics, Llc
Journal of Biomechanics | Year: 2012

The investigation of gait strategies at low gravity environments gained momentum recently as manned missions to the Moon and to Mars are reconsidered. Although reports by astronauts of the Apollo missions indicate alternative gait strategies might be favored on the Moon, computational simulations and experimental investigations have been almost exclusively limited to the study of either walking or running, the locomotion modes preferred under Earth's gravity. In order to investigate the gait strategies likely to be favored at low gravity a series of predictive, computational simulations of gait are performed using a physiological model of the musculoskeletal system, without assuming any particular type of gait. A computationally efficient optimization strategy is utilized allowing for multiple simulations. The results reveal skipping as more efficient and less fatiguing than walking or running and suggest the existence of a walk-skip rather than a walk-run transition at low gravity. The results are expected to serve as a background to the design of experimental investigations of gait under simulated low gravity. © 2012 Elsevier Ltd.

Van Den Bogert A.J.,Orchard Kinetics, Llc | Samorezov S.,Cleveland Clinic | Davis B.L.,Austen BioInnovation Institute | Smith W.A.,Cleveland Clinic
Journal of Biomechanical Engineering | Year: 2012

Advanced prosthetic knees for transfemoral amputees are currently based on controlled damper mechanisms. Such devices require little energy to operate, but can only produce negative or zero joint power, while normal knee joint function requires alternative phases of positive and negative work. The inability to generate positive work may limit the user's functional capabilities, may cause undesirable adaptive behavior, and may contribute to excessive metabolic energy cost for locomotion. In order to overcome these problems, we present a novel concept for an energy-storing prosthetic knee, consisting of a rotary hydraulic actuator, two valves, and a spring-loaded hydraulic accumulator. In this paper, performance of the proposed device will be assessed by computational modeling and by simulation of functional activities. A computational model of the hydraulic system was developed, with methods to obtain optimal valve control patterns for any given activity. The objective function for optimal control was based on tracking of joint angles, tracking of joint moments, and the energy cost of operating the valves. Optimal control solutions were obtained, based on data collected from three subjects during walking, running, and a sit-stand-sit cycle. Optimal control simulations showed that the proposed device allows near-normal knee function during all three activities, provided that the accumulator stiffness was tuned to each activity. When the energy storage mechanism was turned off in the simulations, the system functioned as a controlled damper device and optimal control results were similar to literature data on human performance with such devices. When the accumulator stiffness was tuned to walking, simulated performance for the other activities was sub-optimal but still better than with a controlled damper. We conclude that the energy-storing knee concept is valid for the three activities studied, that modeling and optimal control can assist the design process, and that further studies using human subjects are justified. © 2012 American Society of Mechanical Engineers.

Aurora A.,Cleveland Clinic | Aurora A.,Cleveland State University | McCarron J.A.,Orthopedic Surgery Section | van den Bogert A.J.,Orchard Kinetics, Llc | And 3 more authors.
Journal of Shoulder and Elbow Surgery | Year: 2012

Background: Scaffolds continue to be developed and used for rotator cuff repair augmentation; however, the appropriate scaffold material properties and/or surgical application techniques for achieving optimal biomechanical performance remains unknown. The objectives of the study were to simulate a previously validated spring-network model for clinically relevant scenarios to predict: (1) the manner in which changes to components of the repair influence the biomechanical performance of the repair and (2) the percent load carried by the scaffold augmentation component. Materials and methods: The models were parametrically varied to simulate clinically relevant scenarios, namely, changes in tendon quality, altered surgical technique(s), and different scaffold designs. The biomechanical performance of the repair constructs and the percent load carried by the scaffold component were evaluated for each of the simulated scenarios. Results: The model predicts that the biomechanical performance of a rotator cuff repair can be modestly increased by augmenting the repair with a scaffold that has tendon-like properties. However, engineering a scaffold with supraphysiologic stiffness may not translate into yet stiffer or stronger repairs. Importantly, the mechanical properties of a repair construct appear to be most influenced by the properties of the tendon-to-bone repair. The model suggests that in the clinical setting of a weak tendon-to-bone repair, scaffold augmentation may significantly off-load the repair and largely mitigate the poor construct properties. Conclusions: The model suggests that future efforts in the field of rotator cuff repair augmentation may be directed toward strategies that strengthen the tendon-to-bone repair and/or toward engineering scaffolds with tendon-like mechanical properties. © 2012 Journal of Shoulder and Elbow Surgery Board of Trustees.

Sartori M.,University of Padua | Sartori M.,National Research Council Italy | Reggiani M.,University of Padua | van den Bogert A.J.,Orchard Kinetics, Llc | Lloyd D.G.,Griffith University
Journal of Biomechanics | Year: 2012

We present a robust and computationally inexpensive method to estimate the lengths and three-dimensional moment arms for a large number of musculotendon actuators of the human lower limb. Using a musculoskeletal model of the lower extremity, a set of values was established for the length of each musculotendon actuator for different lower limb generalized coordinates (joint angles). A multidimensional spline function was then used to fit these data. Muscle moment arms were obtained by differentiating the musculotendon length spline function with respect to the generalized coordinate of interest. This new method was then compared to a previously used polynomial regression method. Compared to the polynomial regression method, the multidimensional spline method produced lower errors for estimating musculotendon lengths and moment arms throughout the whole generalized coordinate workspace. The fitting accuracy was also less affected by the number of dependent degrees of freedom and by the amount of experimental data available. The spline method only required information on musculotendon lengths to estimate both musculotendon lengths and moment arms, thus relaxing data input requirements, whereas the polynomial regression requires different equations to be used for both musculotendon lengths and moment arms. Finally, we used the spline method in conjunction with an electromyography driven musculoskeletal model to estimate muscle forces under different contractile conditions, which showed that the method is suitable for the integration into large scale neuromusculoskeletal models. © 2011 Elsevier Ltd.

Kristianslund E.,Norwegian School of Sport Sciences | Krosshaug T.,Norwegian School of Sport Sciences | Van den Bogert A.J.,Orchard Kinetics, Llc
Journal of Biomechanics | Year: 2012

Analyses of joint moments are important in the study of human motion, and are crucial for our understanding of e.g. how and why ACL injuries occur. Such analyses may be affected by artifacts due to inconsistencies in the equations of motion when force and movement data are filtered with different cut-off frequencies. The purpose of this study was to quantify the effect of these artifacts, and compare joint moments calculated with the same or different cut-off frequency for the filtering of force and movement data. 123 elite handball players performed sidestep cutting while the movement was recorded by eight 240. Hz cameras and the ground reaction forces were recorded by a 960. Hz force plate. Knee and hip joint moments were calculated through inverse dynamics, with four different combinations of cut-off frequencies for signal filtering: movement 10. Hz, force 10. Hz, (10-10); movement 15. Hz, force 15. Hz; movement 10. Hz, force 50. Hz (10-50); movement 15. Hz, force 50. Hz. The results revealed significant differences, especially between conditions with different filtering of force and movement. Mean (SD) peak knee abduction moment for the 10-10 and 10-50 condition were 1.27 (0.53) and 1.64 (0.68) Nm/kg, respectively. Ranking of players based on knee abduction moments were affected by filtering condition. Out of 20 players with peak knee abduction moment higher than mean+1. SD with the 10-50 condition, only 11 were still above mean+1. SD when the 10-10 condition was applied. Hip moments were very sensitive to filtering cut-off. Mean (SD) peak hip flexion moment was 3.64 (0.75) and 5.92 (1.80) under the 10-10 and 10-50 conditions, respectively. Based on these findings, force and movement data should be processed with the same filter. Conclusions from previous inverse dynamics studies, where this was not the case, should be treated with caution. © 2011 Elsevier Ltd.

Agency: Department of Health and Human Services | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 93.62K | Year: 2010

DESCRIPTION (provided by applicant): High-fidelity clinical movement analysis with body mounted sensors Summary Clinical movement analysis is an important tool for management of orthopedic and neurological movement disorders. Despite scientific and clinical successes, this tool has not found widespread use in clinical practice outside of major research centers. One reason for this is the high cost of laboratory equipment, which is around 250,000 for optical motion capture with instrumented force platforms or treadmills. A trained technician is needed to collect and process the data. This project will investigate the feasibility of obtaining the same high-fidelity clinical movement analysis by using small, low-cost, and wireless motion sensors, which can reduce the hardware cost by a factor 100. Data will be processed with novel algorithms that integrate motion sensor data from different locations on the body into a mathematical model for musculoskeletal dynamics. The algorithm will solve an entire movement trajectory reliably by constraining the solutions to be consistent with known laws of physics and muscle physiology. Similar model-based algorithms have been used successfully in other fields such as fluid dynamics but not yet for human movement analysis. This Phase 1 project, two aims are included: (1) to develop a prototype of the software which is capable of two-dimensional modeling and analysis, and (2) to test this prototype by collecting data from seven accelerometers and comparing the results to a conventional optical motion capture. If the project is successful, a full three-dimensional analysis, hardware integration, and user interface will be developed in Phase 2. This technology has the potential to revolutionize the industry and make high-quality clinical movement analysis a cost effective and user friendly tool which is readily available to clinicians and physical therapists. PUBLIC HEALTH RELEVANCE: High-fidelity clinical movement analysis with body mounted sensors Relevance The proposed technology will make it possible for clinicians and physical therapists to do an accurate quantitative evaluation of a patient's movement and muscle function, using small wireless motion sensors attached to the patient. While the patient performs movements or exercises, data will be sent to a laptop computer which automatically generates a clinical report. The system including software will be sold for a price of 5000.

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