COMBINED MUSCULO-SKELETAL MULTI-BODY DYNAMICS/FINITE ELEMENT ANALYSIS OF SEVERAL ERGONOMICS AND BIO-MECHANICS PROBLEMS

Within this thesis, two ergonomics (i.e. seating comfort and long-distance driving fatigue problems) and two structural bio-mechanics (i.e. femur-fracture fixation and radius-fracture fixation) problems are investigated using musculo-skeletal multi-body dynamics and finite element computational analyses. Within the seating comfort problem analyzed, a complete-body finite element model is constructed and used to assess the effect of seat geometry and seating posture on the feel of comfort experienced by a seated human. Within the long-distance driving fatigue problem, musculo-skeletal analysis is employed to assess the extent of fatigue experienced by a driver through the evaluation of level of activity of his/her various muscles. Within the femur-fracture fixation problem, physiologically realistic loading conditions associated with active daily activities (i.e. cycling) are employed within a finite-element frame work to assess fracture fixation performance and durability of the implant. Within the radius-fracture fixation problem, the analysis developed within the femur-fracture fixation problem is further related to indicate the effects of other types of loadings (associated with additional daily activities) and improved biological and structural material model are employed. For all cases studied in the present work, relevant experimental data are used to validate the computational procedure employed

Book of Abstracts 15th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering and 3rd Conference on Imaging and Visualization

In this edition, the two events will run together as a single conference, highlighting the strong connection with the Taylor & Francis journals: Computer Methods in Biomechanics and Biomedical Engineering (John Middleton and Christopher Jacobs, Eds.) and Computer Methods in Biomechanics and Biomedical Engineering: Imaging and Visualization (JoãoManuel R.S. Tavares, Ed.). The conference has become a major international meeting on computational biomechanics, imaging andvisualization. In this edition, the main program includes 212 presentations. In addition, sixteen renowned researchers will give plenary keynotes, addressing current challenges in computational biomechanics and biomedical imaging. In Lisbon, for the first time, a session dedicated to award the winner of the Best Paper in CMBBE Journal will take place. We believe that CMBBE2018 will have a strong impact on the development of computational biomechanics and biomedical imaging and visualization, identifying emerging areas of research and promoting the collaboration and networking between participants. This impact is evidenced through the well-known research groups, commercial companies and scientific organizations, who continue to support and sponsor the CMBBE meeting series. In fact, the conference is enriched with five workshops on specific scientific topics and commercial software.info:eu-repo/semantics/draf

Biomechanical musculoskeletal model

Předkládaná práce je zaměřena na svalově-kosterní modelování, především pak na výpočet svalových sil a ramen momentů při libovolném pohybu s využitím nové metody určení průběhů svalů. Jejím hlavním přínosem je vývoj unikátní metody založené na svalovém obepínání anuloidů, která výrazné snižuje nedostatky již existujících metod pro určení svalových trajektorií. Metoda je vyvinuta pro výpočet korektního tvaru svalu při jakékoliv konfiguraci kloubů. Je založena na obecné známé metodě svalového obepínání série překážek tvořených tuhými geometrickými tvary a nahrazujících okolní tkáně, obecné známá jako metoda obstacle-set. Z důvodu vylepšení původní metody byly překážky tvaru koule či válce nahrazeny anuloidy. Nové vzniklá metoda dále umožňuje automatický výpočet umístění svalových úponů; pozic, natočení a poloměrů jednotlivých anuloidů; nárůst aktuálního fyziologického průřezu svalu během kontrakce či změny tvaru svalu s ohledem na sousedící svalové skupiny. Veškerá geometrie metody je založena na MRI a počtu uvažovaných svalových vláken. Dílčím cílem studie je vytvořit jednoduchý model ramene v programu MATLAB, který obsahuje pouze dvojhlavý sval pažní a je založen na nové vyvinuté metodě obepínání anuloidu. Touto cestou je prezentována implementace, použití, výhody a nevýhody této metody. Kosti modelu jsou nahrazeny tuhými tělesy spojenými reálnými klouby; skutečné chování svalů je simulováno modelem Hillova typu. Pro potřeby této práce jsou pohyby lopatky a klíční kosti zanedbány. Svalový komplex je prezentován elastickými svalovými vlákny zanedbatelného tření generující stejnou sílu po celé své délce a obepínající sousední struktury nahrazené anuloidy. Pro validaci modelu a metody obepínání anuloidu je simulován pohyb pažní kosti - abdukce a přední flexe do úhlu 90°. Trajektorie svalových vláken, síly ve svalech, aktuální délka a momentová ramena svalů jsou poté porovnána s výsledky obdobných modelů prezentovaných v literatuře, s elektromyografickým měřením a se dvěma modely ramene sestavených v programu AnyBody Modeling System. Výsledky prokazují úspěšnou validaci hlavních akčních členů abdukce a přední flexe ramene. Nová metoda svalového obepínání anuloidů je vhodnou metodou pro simulaci všech kloubů lidského těla - především pro komplikované klouby jako je např. ramenní komplex, či pro všechny typy svalů - silný, slabý, plochý, dlouhý, krátký, aj. Prezentovaná studie také stručné představuje anatomii a fyziologii ramenního komplexu, nabízí rešerši existujících ramenních modelů a metod pro výpočet svalové trajektorie a do větších detailů popisuje dynamiku vázaných mechanických systémů v prostoru. Závěrem lze říci, že metoda svalového obepínání anuloidů je užitečným nástrojem při svalové-kosterním modelování.NeobhájenoPresented thesis work is focused on musculoskeletal modeling, especially on muscle forces and moment arms calculation using the new method for muscle path determination. This method is based on obstacle-set method. However, the new torus obstacles are implemented instead of standard obstacles such as spheres and cylinders to improve the original process of muscle wrapping. This method also enables the automatic calculation of muscle lines attachments; positions, rotation and radius of torus obstacles originated from MRI and respecting the input number of muscle lines set by the user. The torus-obstacle method also considers the muscle bulging up as well as changes of muscle shapes influenced by surrounding muscles. The case of this study is to create the simple shoulder model in MATLAB including the deltoid muscle and using developed torus-obstacle method. Thanks that, the implementation, usage, advantages and disadvantages of presented method are shown. The bones are modeled by rigid bodies connected by real joints; the real muscle behavior is simulated by Hill-type model. For purpose of this work, the scapula and the clavicle are fixed. The muscle complex is replaced by elastic frictionless muscle lines of action generating the same force along the whole band and wrapping around the neighboring structures replaced by torus obstacles. The humeral abduction and forward flexion till 90° are simulated to validate the model and also the wrapping method. The paths of muscle lines, muscle forces, actual lengths and the muscle moment arms are compared to the similar models published in literature, to the electromyography measurement and to two shoulder models built in AnyBody Modeling System. The results show the successful validation of major actuators of abduction and forward flexion. In addition, the method is absolutely not time-consuming. The new torus-obstacle method is suitable for all human body joints - especially for complicated joints as shoulder complex, for all muscles - thick, thin, shallow, long, short etc. Presented study also introduces briefly the anatomy and physiology of the shoulder complex, offers the research of existing shoulder models and methods for muscle path definition and describes the multibody spatial dynamics in more details. In conclusion, developed torus-obstacle method designed for muscle trajectory computation in musculoskeletal modeling seems to be useful tool

Biomechanics

Biomechanics is a vast discipline within the field of Biomedical Engineering. It explores the underlying mechanics of how biological and physiological systems move. It encompasses important clinical applications to address questions related to medicine using engineering mechanics principles. Biomechanics includes interdisciplinary concepts from engineers, physicians, therapists, biologists, physicists, and mathematicians. Through their collaborative efforts, biomechanics research is ever changing and expanding, explaining new mechanisms and principles for dynamic human systems. Biomechanics is used to describe how the human body moves, walks, and breathes, in addition to how it responds to injury and rehabilitation. Advanced biomechanical modeling methods, such as inverse dynamics, finite element analysis, and musculoskeletal modeling are used to simulate and investigate human situations in regard to movement and injury. Biomechanical technologies are progressing to answer contemporary medical questions. The future of biomechanics is dependent on interdisciplinary research efforts and the education of tomorrow’s scientists

A virtual environment for the modelling, simulation and manufacturing of orthopaedic devices

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The objective of this work is to investigate whether the game physics based modelling is accurate enough to be used in modelling the motion of the human body, in particular musculoskeletal motion. Hitherto, the implementation of game physics in the medical field focused only on anatomical representation for education and training purposes. Introducing gaming platforms and physics engines into orthopaedics applications will help to overcome several difficulties encountered in the modelling of articular joints. Implementing a physics engine (PhysX), which is mainly designed for video games, handles intensive computations in optimized ways at an interactive speed. In this study, the capabilities of the physics engine (PhysX) and gaming platform for modelling and simulating articular joints are evaluated. First, a preliminary validation is carried out for mechanical systems with analytical solutions, before constructing the musculoskeletal model to evaluate the consistency of gaming platforms. The developed musculoskeletal model deals with the human joint as an unconstrained system with 6 DOF which is not available with other joint modeller. The model articulation is driven by contact surfaces and the stiffness of surrounding tissues. A number of contributions, such as contact modelling and muscle wrapping, have been made in this research to overcome some existing challenges in joint modelling. Using muscle segmentation, the proposed technique effectively handles the problem of muscle wrapping, a major concern for many; thus the shortest path and line of action are no longer problematic. Collision behaviour has also shown a stable response for colliding as well as resting objects, provided that it is based on the principles of surface properties and the conservation of linear and angular momentums. The precision of collision detection and response are within an acceptable tolerance controllable by varying the mesh density. An image based analysis system is developed in this thesis, mainly in order to validate the proposed physics based modelling solution. This minimally invasive method is based on the analysis of marker positions located at bony positions with minimal skin movement. The image based system overcomes several challenges associated with the currently existing methods, such as inaccuracy, complication, impracticability and cost. The analysis part of this research has considered the elbow joint as a case study to investigate and validate the proposed physics based model. Beside the interactive 3D simulation, the obtained results are validated by comparing them with the image based system developed within the current research to investigate joint kinematics and laxity and also with published material, MJM and results from experiments performed at the Brunel Orthopaedic Research and Learning Centre. The proposed modelling shows the advantageous speed, reliability and flexibility of the proposed model. It is shown that the gaming platform and physics engine provide a viable solution to human musculoskeletal modelling. Finally, this thesis considers an extended implementation of the proposed platform for testing and assessing the design of custom-made implants, to enhance joint performance. The developed simulation software is expected to give indicative results as well as testing different types of prosthetic implant. Design parameterization and sensitivity analysis for geometrical features are discussed. Thus, an integrated environment is proposed to link the real-time simulation software with a manufacturing environment so as to assist the production of patient specific implants by rapid manufacturing

A novel musculoskeletal joint modelling for orthopaedic applications

This thesis was submitted for the degree of Docter of Philosophy and awarded by Brunel University.The objective of the work carried out in this thesis was to develop analytical and computational tools to model and investigate musculoskeletal human joints. It was recognised that the FEA was used by many researchers in modelling human musculoskeletal motion, loading and stresses. However the continuum mechanics played only a minor role in determining the articular joint motion, and its value was questionable. This is firstly due to the computational cost and secondly due to its impracticality for this application. On the other hand, there isn’t any suitable software for precise articular joint motion analysis to deal with the local joint stresses or non standard joints. The main requirement in orthopaedics field is to develop a modeller software (and its associated theories) to model anatomic joint as it is, without any simplification with respect to joint surface morphology and material properties of surrounding tissues. So that the proposed modeller can be used for evaluating and diagnosing different joint abnormalities but furthermore form the basis for performing implant insertion and analysis of the artificial joints. The work which is presented in this thesis is a new frame work and has been developed for human anatomic joint analysis which describes the joint in terms of its surface geometry and surrounding musculoskeletal tissues. In achieving such a framework several contributions were made to the 6DOF linear and nonlinear joint modelling, the mathematical definition of joint stiffness, tissue path finding and wrapping and the contact with collision analysis. In 6DOF linear joint modelling, the contribution is the development of joint stiffness and damping matrices. This modelling approach is suitable for the linear range of tissue stiffness and damping properties. This is the first of its kind and it gives a firm analytical basis for investigating joints with surrounding tissue and the cartilage. The 6DOF nonlinear joint modelling is a new scheme which is described for modelling the motion of multi bodies joined by non-linear stiffness and contact elements. The proposed method requires no matrix assembly for the stiffness and damping elements or mass elements. The novelty in the nonlinear modelling, relates to the overall algorithmic approach and handling local non-linearity by procedural means. The mathematical definition of joint stiffness is also a new proposal which is based on the mathematical definition of stiffness between two bodies. Based on the joint stiffness matrix properties, number of joint stiffness invariants was obtained analytically such as the centre of stiffness, the principal translational stiffnesses, and the principal rotational stiffnesses. In corresponding to these principal stiffnesses, their principal axes have been also obtained. Altogether, a joint is assessed by six principal axes and six principal stiffnesses and its centre of stiffness. These formulations are new and show that a joint can be described in terms of inherent stiffness properties. It is expected that these will be better in characterising a joint in comparison to laxity based characterisation. The development of tissue path finding and wrapping algorithms are also introduced as new approaches. The musculoskeletal tissue wrapping involves calculating the shortest distance between two points on a meshed surface. A new heuristic algorithm was proposed. The heuristic is based on minimising the accumulative divergence from the straight line between two points on the surface and the direction of travel on the surface (i.e. bone). In contact and collision based development, the novel algorithm has been proposed that detects possible colliding points on the motion trajectory by redefining the distance as a two dimensional measure along the velocity approach vector and perpendicular to this vector. The perpendicular distance determines if there are potentially colliding points, and the distance along the velocity determines how close they are. The closest pair among the potentially colliding points gives the “time to collision”. The algorithm can eliminate the “fly pass” situation where very close points may not collide because of the direction of their relative velocity. All these developed algorithms and modelling theories, have been encompassed in the developed prototype software in order to simulate the anatomic joint articulations through modelling formulations developed. The software platform provides a capability for analysing joints as 6DOF joints based on anatomic joint surfaces. The software is highly interactive and driven by well structured database, designed to be highly flexible for the future developments. Particularly, two case studies are carried out in this thesis in order to generate results relating to all the proposed elements of the study. The results obtained from the case studies show good agreement with previously published results or model based results obtained from Lifemod software, whenever comparison was possible. In some cases the comparison was not possible because there were no equivalent results; the results were supported by other indicators. The modelling based results were also supported by experiments performed in the Brunel Orthopaedic Research and Learning Centre

Musculoskeletal shoulder modelling for clinical applications

The shoulder is the most commonly dislocated joint in the human body, with the vast majority of these dislocations being located anteriorly. Anterior shoulder dislocations are commonly associated with capsuloligamentous injuries and osseous defects. Recurrent anterior instability is a common clinical problem and understanding the influence of structural damage on joint stability is an important adjunct to surgical decision-making. Clinical practice is guided by experience, radiology, retrospective analyses and physical cadaver experiments. As the stability of the shoulder is load dependent, with higher joint forces increasing instability, the aim of this thesis was to develop and validate computational shoulder models to simulate the effect of structural damage on joint stability under in-vivo loading conditions to aid surgical decision-making for patients with anterior shoulder instability. The UK National Shoulder Model, consisting of 21 upper limb muscles crossing 5 functional joints, was customised to accurately quantify shoulder loading during functional activities. Ten subject-specific shoulder models were developed from Magnetic Resonance Imaging and validated against electromyographic signals. These models were used to identify the best combination of anthropometric parameters that yield best model outcomes in shoulder loading through linear scaling of personalised shoulder models. These parameters were gender and the ratio of body height to shoulder width (p<0.04) and these model predictions are significantly improved (p<0.02) when compared to the generic model. The forces derived from the modelling were used in two subject-specific finite element models with an anatomically accurate representation of the labrum, to assess shoulder stability through concavity compression under physiological joint loading for pathologies associated with anterior shoulder instability. The key results from these studies were that there is a high risk of shoulder dislocation under physiological joint loading for patients with a 2 mm anterior or 4 mm anteroinferior osseous defect. The loss in anterior shoulder stability in overhead throwing athletes with intact glenoid following biceps tenodesis is compensated by a non-significant increase in rotator cuff muscle force which maintain shoulder stability across all overhead throwing sports, except baseball pitching, where biceps tenodesis has significantly decreased (p<0.02) anterior shoulder stability. The work in this thesis has advanced the technology of musculoskeletal modelling of the shoulder through the inclusion of concavity compression and has applied this to various relevant clinical questions through the further development of an anatomical atlas, and an atlas of tasks of daily living. The applications of such modelling are broader than those addressed here and therefore this work serves as the foundation for potential further studies, including the bespoke design of arthroplasty or other soft tissue procedures.Open Acces

Description of motor control using inverse models

Humans can perform complicated movements like writing or running without giving them much thought. The scientific understanding of principles guiding the generation of these movements is incomplete. How the nervous system ensures stability or compensates for injury and constraints – are among the unanswered questions today. Furthermore, only through movement can a human impose their will and interact with the world around them. Damage to a part of the motor control system can lower a person’s quality of life. Understanding how the central nervous system (CNS) forms control signals and executes them helps with the construction of devices and rehabilitation techniques. This allows the user, at least in part, to bypass the damaged area or replace its function, thereby improving their quality of life. CNS forms motor commands, for example a locomotor velocity or another movement task. These commands are thought to be processed through an internal model of the body to produce patterns of motor unit activity. An example of one such network in the spinal cord is a central pattern generator (CPG) that controls the rhythmic activation of synergistic muscle groups for overground locomotion. The descending drive from the brainstem and sensory feedback pathways initiate and modify the activity of the CPG. The interactions between its inputs and internal dynamics are still under debate in experimental and modelling studies. Even more complex neuromechanical mechanisms are responsible for some non-periodic voluntary movements. Most of the complexity stems from internalization of the body musculoskeletal (MS) system, which is comprised of hundreds of joints and muscles wrapping around each other in a sophisticated manner. Understanding their control signals requires a deep understanding of their dynamics and principles, both of which remain open problems. This dissertation is organized into three research chapters with a bottom-up investigation of motor control, plus an introduction and a discussion chapter. Each of the three research chapters are organized as stand-alone articles either published or in preparation for submission to peer-reviewed journals. Chapter two introduces a description of the MS kinematic variables of a human hand. In an effort to simulate human hand motor control, an algorithm was defined that approximated the moment arms and lengths of 33 musculotendon actuators spanning 18 degrees of freedom. The resulting model could be evaluated within 10 microseconds and required less than 100 KB of memory. The structure of the approximating functions embedded anatomical and functional features of the modelled muscles, providing a meaningful description of the system. The third chapter used the developments in musculotendon modelling to obtain muscle activity profiles controlling hand movements and postures. The agonist-antagonist coactivation mechanism was responsible for producing joint stability for most degrees of freedom, similar to experimental observations. Computed muscle excitations were used in an offline control of a myoelectric prosthesis for a single subject. To investigate the higher-order generation of control signals, the fourth chapter describes an analytical model of CPG. Its parameter space was investigated to produce forward locomotion when controlled with a desired speed. The model parameters were varied to produce asymmetric locomotion, and several control strategies were identified. Throughout the dissertation the balance between analytical, simulation, and phenomenological modelling for the description of simple and complex behavior is a recurrent theme of discussion

Musculoskeletal Models in a Clinical Perspective

This book includes a selection of papers showing the potential of the dynamic modelling approach to treat problems related to the musculoskeletal system. The state-of-the-art is presented in a review article and in a perspective paper, and several examples of application in different clinical problems are provided

Development of an inverse musculoskeletal model of the wrist

The wrist is a complex mechanical system that plays a crucial role in many activities of daily living. Some pathologies that affect the wrist are mechanically instigated or propagated, like osteoarthritis, and can have significant effects on quality of life. The small size of the joint complex precludes some of the investigative techniques that are employed in investigating lower-limb pathology. One way to gain understanding of the biomechanics of the system is to create a computational model to perform investigations that cannot be carried out in vivo. The ambition is to apply an inverse musculoskeletal model of the wrist, previously developed at Imperial College London and implemented using a novel anatomical data set, to answer clinical questions by using biomechanical research to inform intervention. As a key input to the model is joint kinematics, the formation of the joint coordinate system (JCS) used to collect upper limb kinematics was a primary focus of this thesis. The recommendations for building the coordinate system commonly used, published by the International Society of Biomechanics (ISB), are difficult to implement in vivo as they depend on observations only feasible with cadavers. Likewise, the model uses the natural anatomical axes identified by calculating screw displacement axes of passive motions of a cadaveric wrist and thus the axes may differ from axes defined in vivo. Inconsistencies in the relative position and orientation of these axes in the literature raised the question of whether their in vitro definition would match the in vivo definition. A study was conducted to investigate the relative position and orientation of the natural axes of the wrist and to create an alternate joint coordinate system for the wrist using readily palpable anatomical landmarks of the hand and forearm. Participants performed flexion-extension (FE) and radial-ulnar deviation (RUD) motions with their dominant limb, both unrestricted and with a single-plane constraint, as well as pronation- supination (PS) and dart throwing motion. The muscle activities for the flexor digitorum superficialis, flexor carpi ulnaris, flexor carpi radialis, pronator teres, extensor digitorum communis, extensor carpi ulnaris, and extensor carpi radialis were recorded using surface electromyography (EMG). It was determined that defining the axes of the wrist with a prescribed motion pathway produces different results to unconstrained in vivo motion. The mean distance between the unconstrained FE and RUD axes, in the direction of the long axis of the forearm, was 2.5 ± 3.9mm and this was statistically different (p < 0.03) from that of the constrained axes (1.6 ± 4.0mm). The mean angular distance in the plane perpendicular to the long axis of the forearm was 53.2 ± 10.8◦. Again, this was statistically different (p < 0.001) from the constrained axes where the angular difference was 107.8 ± 17.7◦. The distance and angular difference between the constrained FE axis with the unconstrained RUD axis were similar to those documented in the literature. This suggests that the reason for the inconsistencies is that the motions were performed in different ways, rather than that they resulted from anatomical differences. Proposed alternate joint coordinate systems were compared to the ISB recommended system. Landmark palpation repeatability, axes direction repeatability, and amount of secondary rotation (e.g. rotation in RUD and PS axes during FE) were the metrics used to compare the systems. No difference was found between the ISB recommended JCS and those created as part of the study in any of the three metrics. This means that, for the given metrics, the proposed JCSs performed as well as the ISB recommended system and thus could be used instead, making the quantification of kinematics more feasible in a clinical setting. As a result, I recommend that an alternate JCS that uses the medial and lateral epicondyles, radial and ulnar styloids, the base of the third metacarpal, and the heads of the second and fifth metacarpal is used for in vivo clinical and research use. EMG signals were normalised by activity during maximal voluntary contraction (MVC) of the observed muscles. Nine tasks, selected from the literature, were performed and the task most likely to elicit MVC in each muscle was noted. The non-dominant limb was also investigated to determine whether dominance had an effect on the task most likely to elicit MVC. Dominance had limited effect with statistical differences being found only in the finger flexors and extensors (p < 0.031). Tasks most likely to elicit MVC were identified for each muscle. These results can be used to produce MVC protocols tailored to the muscles being investigated, can help check for crosstalk during electrode placement, and show that limb dominance needs to be considered when recording EMG for the finger muscles. The collected MVCs were used to normalise the EMG data that are presented in the thesis. It was found that the EMG pattern for each participant was statistically different from the others (p< 0.001) meaning that each individual employs a unique neuromuscular control algorithm for motions of the wrist. The primary differences were levels of co-contraction. This was consistent within the participants’ trials which suggests that there may be an anatomical reason for the level of co-contraction as this would be unique to each participant. The EMG data were also used to validate a musculoskeletal model of the wrist, previously developed at Imperial College, for in vivo applications. The kinematics for each participant were input into the model and the muscle forces were calculated. Simulated muscle activity was then calculated by normalising the muscle force by the maximum muscle force for each muscle. Five simulated muscle activities could be compared with the EMG data. The simulated muscle activity patterns matched the recorded EMG patterns both qualitatively and quantitatively, using statistical parameter mapping. No statistical difference was found between the recorded and simulated muscle activity. Thus the model is considered to be valid for predicting muscle activity during in vivo motion of the wrist. Though there was poor correlation between the model results and the EMG (r |0.65|), with the model producing the pattern with the smaller magnitude. It is hypothesised that this is again due to the lack of co-contraction, as agonist muscles would need to be more active to counter the forces generated by antagonists. Thus a JCS for the wrist that is employable in a clinical setting and performs as well as the ISB JCS has been identified; muscle activation patterns for the wrist have been identified; and the Imperial College London wrist model has been validated for in vivo use.Open Acces