Publications
157 results found
Montanino A, Modenese L, Gopalakrishnan A, et al., 2015, Smoothing or filtering marker trajectories? The effects on calculated joint moments, XXV Congress of the International Society of Biomechanics
Villette CC, Phillips ATM, Zaharie DT, 2015, Frangible optimised lower limb surrogate for assessing underbelly blast injury, International Research Council on Biomechanics of Injury
Phillips ATM, Villette CC, Modenese L, 2015, Femoral bone mesoscale structural architecture prediction using musculoskeletal and finite element modelling, International Biomechanics, Vol: 2, Pages: 43-61, ISSN: 2333-5432
Through much of the anatomical and clinical literature bone is studied with a focus on its structural architecture, while it is rare for bone to be modelled using a structural mechanics as opposed to a continuum mechanics approach in the engineering literature. A novel mesoscale structural model of the femur is presented in which truss and shell elements are used to represent trabecular and cortical bone, respectively. Structural optimisation using a strain-based bone adaptation algorithm is incorporated within a musculoskeletal and finite element modelling framework to predict the structure of the femur subjected to two loading scenarios; a single load case corresponding to the frame of maximum hip joint contact force during walking and a full loading regime consisting of multiple load cases from five activities of daily living. The use of the full loading regime compared to the single load case has a profound influence on the predicted trabecular and cortical structure throughout the femur, with dramatic volume increases in the femoral shaft and the distal femur, and regional increases at the femoral neck and greater trochanter in the proximal femur. The mesoscale structural model subjected to the full loading regime shows agreement with the observed structural architecture of the femur while the structural approach has potential application in bone fracture prediction, prevention and treatment. The mesoscale structural approach achieves the synergistic goals of computational efficiency similar to a macroscale continuum approach and a resolution nearing that of a microscale continuum approach.
Villette CC, Phillips ATM, 2015, Predictive mesoscale structural modelling of bone informed by microscale poroelastic analyses, XXV congress of the International Society of Biomechanics
Zaharie D, Villette C, Phillips A, 2015, FRANGIBLE OPTIMISED LOWER LIMB SURROGATE FOR ASSESSING INJURY CAUSED BY UNDERBELLY BLAST, XV International Symposium on Computer Simulation in Biomechanics
Gopalakrishnan A, Modenese L, Phillips ATM, 2014, A novel computational framework for deducing muscle synergies from experimental joint moments, Frontiers in Computational Neuroscience, ISSN: 1662-5188
Prior experimental studies have hypothesized the existence of a ‘muscle synergy’ based control scheme for producing limb movements and locomotion in vertebrates. Such synergies have been suggested to consist of fixed muscle grouping schemes with the co-activation of all muscles in a synergy resulting in limb movement. Quantitative representations of these groupings (termed muscle weightings) and their control signals (termed synergy controls) have traditionally been derived by the factorization of experimentally measured EMG. This study presents a novel approach for deducing these weightings and controls from inverse dynamic joint moments that are computed from an alternative set of experimental measurements – movement kinematics and kinetics. This technique was applied to joint moments for healthy human walking at 0.7 and 1.7 m/s, and two sets of ‘simulated’ synergies were computed based on two different criteria (1) synergies were required to minimize errors between experimental and simulated joint moments in a musculoskeletal model (pure-synergy solution) (2) along with minimizing joint moment errors, synergies also minimized muscle activation levels (optimal-synergy solution). On comparing the two solutions, it was observed that the introduction of optimality requirements (optimal-synergy) to a control strategy solely aimed at reproducing the joint moments (pure-synergy) did not necessitate major changes in the muscle grouping within synergies or the temporal profiles of synergy control signals. Synergies from both the simulated solutions exhibited many similarities to EMG derived synergies from a previously published study, thus implying that the analysis of the two different types of experimental data reveals similar, underlying synergy structures.
Gopalakrishnan A, Modenese L, Phillips ATM, 2014, A dynamic simulation approach for computing muscle synergies from joint moments, 12th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering
Gopalakrishnan A, Phillips ATM, Higginson JS, et al., 2014, Predictive simulations of movement for informing rehabilitation programmes, 12th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering
Geraldes DM, Phillips ATM, 2014, A comparative study of orthotropic and isotropic bone adaptation in the femur, International Journal for Numerical Methods in Biomedical Engineering, Vol: 30, Pages: 873-889, ISSN: 2040-7947
Functional adaptation of the femur has been studied extensively by embedding remodelling algorithms in finite element models, with bone commonly assumed to have isotropic material properties for computational efficiency. However, isotropy is insufficient in predicting the directionality of bone's observed microstructure. A novel iterative orthotropic 3D adaptation algorithm is proposed and applied to a finite element model of the whole femur. Bone was modelled as an optimised strain-driven adaptive continuum with local orthotropic symmetry. Each element's material orientations were aligned with the local principal stress directions and their corresponding directional Young's moduli updated proportionally to the associated strain stimuli. The converged predicted density distributions for a coronal section of the whole femur were qualitatively and quantitatively compared with the results obtained by the commonly used isotropic approach to bone adaptation and with ex vivo imaging data. The orthotropic assumption was shown to improve the prediction of bone density distribution when compared with the more commonly used isotropic approach, whilst producing lower comparative mass, structurally optimised models. It was also shown that the orthotropic approach can provide additional directional information on the material properties distributions for the whole femur, an advantage over isotropic bone adaptation. Orthotropic bone models can help in improving research areas in biomechanics where local structure and mechanical properties are of key importance, such as fracture prediction and implant assessment.
Barzan M, Modenese L, Gopalakrishnan A, et al., 2014, The effect of footwear on the running kinematics, kinetics and knee internal loads: a preliminary study., 7th World Congress of Biomechanics
Villette CC, Phillips ATM, Modenese L, 2014, Combined musculoskeletal and finite element predictive modelling of bone structure and simple fracture analysis, 12th international symposium on Computer Methods in Biomechanics and Biomedical Engineering
Villette CC, Phillips ATM, 2014, Towards a patient-specific combined musculoskeletal and finite element model of bone structure, 2nd UK Patient Specific Modelling Meeting - IPEM conferences
Villette CC, Phillips ATM, 2014, Combined finite element and musculoskeletal predictive structural modelling of the femur: Potential mechanobiology applications, 11th World Congress on Computational Mechanics
Villette CC, Phillips ATM, 2014, Combined predictive structural finite element and musculoskeletal modeling of bone structure for study of fracture under solid blast condition, IStructE Young Researchers' Conference
Gilroy D, Younge AM, Phillips ATM, et al., 2014, Characterisation and Validation of Sawbones Artificial Composite Femur Material, World Congress of Biomechanics
Sawbones 4th Generation composite bones are useful tools for the mechanical testing of orthopaedic devices and validation of FE models. The products are intended to provide more reliability and less variability than cadaveric specimens, and are often used in biomechanical analyses. However, no independent validation of the manufacturer quoted material properties exists. Three point bending tests on the cortical component of the femur and on sheets of the same material were conducted in two independent laboratories to determine the Young’s modulus of the material. These data were incorporated into a FE model of a femur to be validated against an equivalent mechanical test using both force-displacement and strain gauge data. There was significant inter-sample variability in Young’s modulus, potentially due to microstructural heterogeneity. All samples were longitudinally significantly less stiff than the manufacturer quoted value of 16.0 GPa (Sawbones 2014), with a mean Young’s modulus of 10.7 GPa calculated for the cortical sample and 8.4 GPa for the sheets. The FE model compared favourably with the mechanical testing, with a 3.3% higher stiffness than that recorded experimentally, giving confidence in our Young’s modulus data. This paper has highlighted that that care must be taken when employing these products as substitutes for cadaveric specimens.
Barzan M, Modenese L, Gopalakrishnan A, et al., 2014, The Effect of Footwear on Running Kinematics, Kinetics and Knee Internal Loads: a Preliminary Study, World Congress of Biomechanics
Introduction:Musculoskeletal models can yield insight on injury mechanisms by estimating the magnitudes of internal loads (muscle and joint contact forces) and their variation with movement characteristics, e.g. strike pattern (Rooney and Derrick, 2013) and footwear. We present a preliminary investigation into the differences between running barefoot, “minimalist”, with “thick wedge” shoes, based on the kinematics, kinetics and internal knee joint loading computed by a musculoskeletal model of the lower limb.Methods:A healthy experienced runner (age: 24, height: 1.79 m, mass: 87.2 kg) performed 8-10 trials of barefoot, minimalist (VivoBarefoot Aqua Lite) and shod (Nike Impax) shoes running at 3.3 m/s. Initial contact was forefoot, midfoot and rearfoot for barefoot, minimalist and shod running respectively. A Vicon camera system, a high speed video camera and a Kistler force plate recorded kinematics and kinetics during trials. Segment lengths, inertial parameters and muscle maximum isometric forces of an OpenSim model were personalized. A simulation pipeline then computed joint angles, joint moments, muscle activations and joint contact force (JCF) magnitudes.Results:Average results for the three running styles were plotted against a normalized time period between right heel strike and left heel strike, where an average time range corresponding to the active peak of vertical ground reaction forces (27-33% of the considered running gait cycle - pink band in Figure 1) was identified. Extension moments at the knee and ankle joints are shown in Figure 1 for all running styles. Shod running displayed greatest knee extension moment and highest peak monoarticular extensor (vastus lateralis and intermedius) activations, but peak activations in the biarticular gastrocnemii were the lowest (not shown).Discussion:Despite yielding the highest knee extensor muscle forces, the ankle plantar-flexor moment was lowest for shod running and so was the peak knee
Geraldes DM, Phillips ATM, 2014, Topological Influence of Different Load Cases in Femur Adaptation, World Congress of Biomechanics
An iterative orthotropic strain-driven adaptation algorithm [1] was run for a continuum finite element model of a whole femur undergoing 40 frames of level walking and 40 frames of stair climbing. An envelope containing maximum driving stimuli was calculated by selecting the strain values for the guiding frame in each element. The guiding frame was selected as the frame in which the highest absolute normal strain value occurred).The guiding frames are shown red to blue with blue being further through the cycle for each activity modelled, level walking (a) and stair climbing (b), in order to highlight the topological influence of each of the load cases in the whole femur (Figure 1). It is observed that both load cases contribute to the converged orthotropic material properties. Level walking is shown to influence the regions of the femoral head, inferior part of the femoral neck, greater trochanter, posterior-lateral aspects of the femoral shaft and posterior side of the condylar region. The stimulus produced by the stair climbing activity is shown to be dominant in the regions of the superior part of the femoral neck, lesser trochanter, medial aspect of the cortical shaft and anterior side of the distal femur. Analysis of the coronal sections of the whole femur (c), proximal region (d) and distal region (e) emphasise the contribution of both load cases in regions such as the inter-trochanteric region or the epiphyseal line in the condyles. The material properties of the femoral shaft and the femoral neck seem to be influenced by both load cases.Future work should include more daily activities in order to improve the predictions. Nevertheless, the contribution of both load cases to the converged material properties in vast, independent regions of the femur is clear. Thus, it is recommended that multiple frames from different load cases are considered when predicting bone adaptation, with studies that have not done so possibly missing out on the effect of other daily
Villette C, Modenese L, Phillips ATM, 2014, Combined finite element and musculoskeletal predictive structural modelling of the femur: Potential mechanobiology applications
Modenese L, Phillips ATM, Bull AMJ, 2014, Letter to the Editor: In Response to ‘‘Consistency Among Musculoskeletal Models: Caveat Utilitor’’, Annals of Biomedical Engineering, ISSN: 1573-9686
Modenese L, Gopalakrishnan A, Phillips ATM, 2013, Falsification of a lower limb model predicting hip contact force vectors, XXIV Congress of the International Society of Biomechanics
Gopalakrishnan A, Modenese L, Phillips ATM, 2013, Generating computer simulations of movement using muscle synergy inputs
Gopalakrishnan A, Modenese L, Phillips ATM, 2013, Generating computer simulations of movement using muscle synergy inputs, International Society of Biomechanics
Villette CC, Thibon A, Modenese L, et al., 2013, Combined musculoskeletal and finite element modelling of the femur, International Society of Biomechanics
In the 1870’s, Wolff formulated a ‘trajectory theory’ about trabecular bone architecture which can be succinctly written as follows: bone adapts its structure to loading conditions in a way that follows principal stress trajectories. In this study, it was assumed that the human femur is optimally adapted to the loading conditions experienced during daily activities such as walking or climbing stairs. Hence, an initially randomized structural mesoscale model of a femur was iteratively adapted to the loading conditions experienced during a range of daily activities. The resulting structure shows a good visual comparison with clinical observation and the model proved computationally efficient.
Modenese L, Gopalakrishnan A, Lloyd DG, et al., 2013, Falsification of a lower limb model predicting hip contact force vectors, International Society of Biomechanics
Sperry MM, Phillips ATM, McGrgeor AH, 2013, Preliminary classification of joint activation following a postural disturbance, International Society of Biomechanics
van Arkel RJ, Modenese L, Phillips ATM, et al., 2013, Hip Abduction Can Prevent Posterior Edge Loading of Hip Replacements, Journal of Orthopaedic Research, Vol: 31, Pages: 1172-1179, ISSN: 1554-527X
Edge loading causes clinical problems for hard-on-hard hip replacements, and edge loading wear scars are present on the majority of retrieved components. We asked the question: are the lines of action of hip joint muscles such that edge loading can occur in a well-designed, well-positioned acetabular cup? A musculoskeletal model, based on cadaveric lower limb geometry, was used to calculate for each muscle, in every position within the complete range of motion, whether its contraction would safely pull the femoral head into the cup or contribute to edge loading. The results show that all the muscles that insert into the distal femur, patella, or tibia could cause edge loading of a well-positioned cup when the hip is in deep flexion. Patients frequently use distally inserting muscles for movements requiring deep hip flexion, such as sit-to-stand. Importantly, the results, which are supported by in vivo data and clinical findings, also show that risk of edge loading is dramatically reduced by combining deep hip flexion with hip abduction. Patients, including those with sub-optimally positioned cups, may be able to reduce the prevalence of edge loading by rising from chairs or stooping with the hip abducted.
Villette CC, Phillips ATM, Modenese L, 2013, Combined Musculoskeletal and Finite Element Modelling of the Femur, XXIV Congress of the International Society of Biomechanics
Modenese L, Gopalakrishnan A, Phillips ATM, 2013, Application of a falsification strategy to a musculoskeletal model of the lower limb and accuracy of the predicted hip contact force vector, Journal of Biomechanics, Vol: 46, Pages: 1193-1200
In the literature, lower limb musculoskeletal models validated against in vivo measured hip contact forces (HCFs) exhibit a tendency to overestimate the HCFs magnitude and predict inaccurate components of the HCF vector in the transverse plane. In order to investigate this issue, a musculoskeletal model was forced to produce HCFs identical to those measured and the resulting joint equilibrium equations were studied through both a general approach and a static optimization framework. In the former case, the existence of solutions to the equilibrium equations was investigated and the effect of varying the intersegmental moments and the muscle tetanic stress assessed: for a value of 100 N/cm2 and moments calculated from an inverse dynamics analysis on average only 62% of analyzed frames were solvable for level walking and 70% for stair climbing. In the static optimization study, the model could reproduce the experimental HCFs but the recruited muscles were unable to simultaneously equilibrate the hip intersegmental moments without the contribution of reserve moment actuators. Without constraints imposed on the HCFs, the predicted HCF vectors presented maximum angle deviations up to 22° for level walking and 33° for stair climbing during the gait stance phase. The influence of the medio-lateral HCF component on the solvability of the equilibrium equations and the muscle recruitment alteration when the model was forced to produce the experimental HCFs suggest that a more accurate geometrical representation of the gluteal muscles is mandatory to improve predictions of the HCF vector yielded by the static optimization technique.
Phillips ATM, 2012, Structural Optimisation: Biomechanics of the Femur, Engineering and Computational Mechanics, Vol: 165, Pages: 147-154, ISSN: 1755-0777
A preliminary iterative 3D meso-scale structural model of the femur was developed, in which bar and shell elements were used to represent trabecular and cortical bone respectively. The crosssectionalareas of the bar elements and the thickness values of the shell elements were adjustedover successive iterations of the model based on a target strain stimulus, resulting in an optimised construct. The predicted trabecular architecture, and cortical thickness distribution showed good agreement with clinical observations, based on the application of a single leg stance load caseduring gait. The benefit of using a meso-scale structural approach in comparison to micro ormacro-scale continuum approaches to predictive bone modelling was achievement of thesymbiotic goals of computational efficiency and structural description of the femur.
Modenese L, Phillips ATM, 2012, Prediction of hip contact forces and muscle activations during walking at different speeds., Multibody System Dynamics, Vol: 28, Pages: 157-168
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