Numerical investigation of bone adaptation to exercise and fracture in Thoroughbred racehorses

Third metacarpal bone (MC3) fracture has a massive welfare and economic impact on horse racing, representing 45% of all fatal lower limb fractures, which in themselves represent more than 80% of reasons for death or euthanasia on the UK racecourses. Most of these fractures occur due to the accumulation of tissue fatigue as a result of repetitive loading rather than a specific traumatic event. Despite considerable research in the field, including applying various diagnostic methods, it still remains a challenge to accurately predict the fracture risk and prevent this type of injury. The objective of this thesis is to develop computational tools to quantify bone adaptation and resistance to fracture, thereby providing the basis for a viable and robust solution. Recent advances in subject-specific finite element model generation, for example computed tomography imaging and efficient segmentation algorithms, have significantly improved the accuracy of finite element modelling. Numerical analysis techniques are widely used to enhance understanding of fracture in bones and provide better insight into relationships between load transfer and bone morphology. This thesis proposes a finite element based framework allowing for integrated simulation of bone remodelling under specific loading conditions, followed by the evaluation of its fracture resistance. Accurate representation of bone geometry and heterogeneous material properties are obtained from calibrated computed tomography scans.The material mapping between CT-scan data and discretised geometries for the finite element method is carried out by using Moving Least Squares approximation and L2-projection. Thus is then used for numerical investigations and assessment of density gradients at the common site of fracture. Bone is able to adapt its density to changes in external conditions. This property is one of the most important mechanisms for the development of resistance to fracture. Therefore, a finite element approach for simulating adaptive bone changes (also called bone remodelling) is proposed. The implemented method is based on a phenomenological model of the macroscopic behaviour of bone based on the thermodynamics of open systems. Numerical results showed that the proposed technique has the potential to accurately simulate the long-term bone response to specified training conditions and also improve possible treatment options for bone implants. Assessment of the fracture risk was conducted with crack propagation analysis. The potential of two different approaches was investigated: smeared phase-field and discrete configurational mechanics approach. The popular phase-field method represents a crack by a smooth damage variable leading to a phase-field approximation of the variational formulation for brittle fracture. A robust solution scheme was implemented using a monolithic solution scheme with arc-length control. In the configurational mechanics approach, the driving forces, and fracture energy release rate, are expressed in terms of nodal quantities, enabling a fully implicit formulation for modelling the evolving crack front. The approach was extended for the first time to capture the influence of heterogeneous density distribution. The outcomes of this study showed that discrete and smeared crack approximations are capable of predicting crack paths in three-dimensional heterogeneous bodies with comparable results. However, due to the necessity of using significantly finer meshes, phase-field was found to be less numerically efficient. Finally, the current state of the framework's development was assessed using numerical simulations for bone adaptation and subsequent fracture propagation, including analysis of an equine metacarpal bone. Numerical convergence was demonstrated for all examples, and the use of singularity elements proved to further improve the rate of convergence. It was shown that bone adaptation history and bone density distribution influence both fracture resistance and the resulting crack path. The promising results of this study offer a~novel framework to simulate changes in the bone structure in response to exercise and quantify the likelihood of a fracture

Osiąganie kompromisu potrzeb człowieka i przyrody

The article has exhibited that ecoengineering, consisting of the scheduled transformation of ecological systems is an alternate and equivalent method for handling natural environment in contrary to environmental technology, which consists of ecosystems protection against human activity. The human activity in the natural environment may consist of devastating, transforming, or protection trials. In a frame of protection (environmental technology) are attempts on limiting anthropopression, which means the influence of man on the natural environment by various restrictions - technological, legal, and ethical. Up to now transforming natural environment was considered as a necessary evil, connected with the technological impossibility to avoid anthropopression or political necessity to satisfy human needs. The attention of researchers engaged in human activities in the natural environment was focused on criticizing of destruction and diverse propositions to stop this destruction, mainly by protectoral actions. Transforming the environment by man was generally considered a part of the destruction process. So there were trials of counteractions or tolerating it as unavoidable, trying to diminish their effect on the natural environment. Positive possibilities connected with planned and system ie transformation of the natural environment were not noticed, especially possibilities of achieving a compromise between human and nature needs. That such a compromise is possible is proving described there in detail examples of Konin lakes and Biebrza swamps. Ecoengineering conception presented in this dissertation generally values up environment transforming, that therefore is a no more necessary evil but becomes an equivalent and alternate action to environment technology (nature protection). Justification of this thesis is achieved by the demonstration that actions limited to environment technology only can be equally destructive for the environment as out of control wastewaters and pollution dumping. This is demonstrated in the article by an example of Sudety forests, devastated by acid rains and the problem of increasing deficit of sulfur in the soil, caused by introducing Sulphur removing from waste gas technology on a mass scale. The article has exhibited that absolute separation of industrial activity from the natural environment is not possible, that is total anthropopression eliminating. Speaking colloquially closing „anthropopression dragon" in a hermetic cave and draw only consumer satisfaction is not possible. Unavoidable is anthropopression connected with emissions of different forms of energy (heat, noise, electromagnetic fields) and matter (steam, carbon dioxide, wastes) and physical biotopes transforming. The only way in this situation is to incorporate anthropopression sources into ecosystems and turn wastes into fertilizers using ecoengineering. To this goal are tending eventually activities realized in frames of Pure Production and environment managing system according to ISO 14001, propagated today as balanced development conception, and diverse forms of so-named active protection, that can be considered as not fully conscious, limited ecoengineering. More, subsequent operations in environmental technology, from that every one eliminates negative effects of previous, are giving ecoengineering effects too, that is including human activity into the natural environment and creation of new, unstable ecological balances. An example can serve discussed in the article sequence of environment technologies: dust removal - desulphurization - production and distribution of sulphuric fertilizers. Method of such „successive environment technologies approximating to eco-engineering" is however much more costly and dangerous form an and nature than could be preamplified ecoengineering practice, what was pointed out too. The ethical basis for ecoengineering could be the principle „we have the right to be there". The biggest transformation of our planet's environment was the replacement of the atmosphere from oxygen-free to oxygenated realized by blue-green algae (Cyanophyta). There is no cause to regard human rights as lesser than algae rights.  The author of the article has no intention to claim that ecoengineering is better and more perfect practice than environment technology, who therefore should withdraw and be neglected. Ecoengineering as proceeding equivalent and alternative to environment technology should be considered as equal in every situation where a given ecosystem is influenced by anthropopression. Therefore in this dissertation ecoengineering is not discussed individually but in contact with environment technology as „alternative ecoengineering". Only by considering and deciding about ecoengineering alternatives we can choose the more appropriate method of handling with the natural environment. The author assumes that this is the only method that makes possible correct environment evaluation and selection of the best possible technology. Ecoengineering conception based on creating unstable biological balances, formulated as an ecoengineering alternative is significant, new contribution to systems sozology and other philosophical disciplines connected with ecological problems - philosophy of nature, philosophy of technology, and ecophilosophy and ecological ethic. That situation creates a wide perspective for farther researches, primarily connected with the elimination of one-sided environment technology from sozology, ecophilosophy, and environmental ethics and next creating ethical rules Environment transforming. It seems that ecoengineering may give significant research impulse for the philosophy of technology, which will intensify conceptions of valuating technology, today criticized. Extensive possibilities for researches are connected with precision and developing aspects diverse of ecoengineering as interdisciplinary and system ie science, that in this dissertation, focused on motivating ecoengineering could be signaled only. Ecoengineering can be currently utilized in engineers and designers practice and in environment evaluating system s, provided that corresponding procedures and research methods are created within detailed sciences. There are existing also wide possibilities to explore, discover, and research spontaneous ecoengineering effects, that so far have escaped researchers' notice. Similar site surveys can be run in other parts of Poland or other lands. Therefore yielding conclusions can lead to significant theoretical revaluation and substantially change existing engineering and legal practice. The main research problem is ecosystem modeling for ecoengineering needs. Ecoengineering is a new chance for humanity and nature

Dzieci urodzone z zarodków przechowywanych w stanie zamrożenia przez 10 lat. Analiza 5 przypadków

Faced with a scientific and legal debate on human embryo cryopreservation in Poland we show 5 documented clinical cases of successful thawing and transfer of embryos cryopreserved for a long period of time (8-11 years), resulting in successful delivery by the biological or the recipient mother. Cases described include patients with different infertility diagnoses, subjected to different hormonal stimulation treatments. Different oocyte fertilization methods were performed, and the obtained embryos were frozen after 2, 3 or 4 days of in vitro culture using methods employing various cryoprotective agents and freezing curves. As a result of performed thawing and transfer procedures normal, healthy babies were born. Our results are consistent with the international reports on successful long-term storage of embryos, (including the longest known period of over 19 years) resulting in no detectable reduction of the developmental potential after thawing. In light of data shown here, we do not see any medical or biological reasons for legally-regulated limitation of the period of frozen embryo storage. Moreover, if frozen, long-term stored embryos are not threatened by destruction band if prenatal adoption is a real, clinically documented option, we fail to see any reason for legal limitations of embryo cryopreservation in human infertility treatment.W kontekście naukowej i legislacyjnej debaty dotyczącej kriokonserwacji zarodków człowieka w Polsce przedstawiamy 5 udokumentowanych przypadków wieloletniego (przez okres 8-11 lat), skutecznego przechowywania zarodków zakończonego urodzeniem dzieci przez ich biologiczną matkę lub przez matkę adopcyjną. W opisanych przypadkach diagnozowano rożne przyczyny niepłodności. Zastosowano rożne metody hormonalnej stymulacji. Zamrażane były zarodki w rożnych stadiach rozwoju po hodowli in vitro trwającej 2, 3 lub 4 dni, przy udziale rożnych środków osłaniających. W efekcie przeprowadzonych kriotransferów urodziły się zdrowe, prawidłowo rozwinięte dzieci. Przedstawione dane potwierdzają wcześniejsze międzynarodowe doniesienia o możliwości wieloletniego przechowywania (najdłuższy znany przypadek to 19 lat) zamrożonych zarodków bez uszczerbku dla ich zdolności życiowych. W świetle tych danych nie znajdujemy biologicznych czy medycznych przesłanek do ustawowego ograniczania okresu przechowywania kriokonserwowanych zarodków. Tym samym, skoro zamrożone zarodki nie są skazane na biologiczną degradację a ich prenatalna adopcja jest absolutnie realną możliwością, nie widzimy podstaw do prawnego ograniczania stosowania metody kriokonserwacji w leczeniu niepłodności

A computational framework for crack propagation in spatially heterogeneous materials

This paper presents a mathematical formulation and numerical modelling framework for brittle crack propagation in heterogeneous elastic solids. Such materials are present in both natural and engineered scenarios. The formulation is developed in the framework of configurational mechanics and solved numerically using the finite-element method. We show the methodology previously established for homogeneous materials without the need for any further assumptions. The proposed model is based on the assumption of maximal dissipation of energy and uses the Griffith criterion; we show that this is sufficient to predict crack propagation in brittle heterogeneous materials, with spatially varying Young’s modulus and fracture energy. Furthermore, we show that the crack path trajectory orientates itself such that it is always subject to Mode-I. The configurational forces and fracture energy release rate are both expressed exclusively in terms of nodal quantities, avoiding the need for post-processing and enabling a fully implicit formulation for modelling the evolving crack front and creation of new crack surfaces. The proposed formulation is verified and validated by comparing numerical results with both analytical solutions and experimental results. Both the predicted crack path and load–displacement response show very good agreement with experiments where the crack path was independent of material heterogeneity for those cases. Finally, the model is successfully used to consider the real and challenging scenario of fracture of an equine bone, with spatially varying material properties obtained from CT scanning

MoFEM: an open source, parallel finite element library

No abstract available

MoFEM: an open source, parallel finite element library

No abstract available

Multifield finite strain plasticity : theory and numerics

Motivated by the inability of classical computational plasticity to fully exploit modern scientific computing, a multifield formulation for finite strain plasticity is presented. This avoids a local integration of the elastoplastic model. In the multifield approach, the balance of linear momentum, the flow relation and the Karush–Kuhn–Tucker constraints are collectively cast in a variational format. In addition to the deformation, both the plastic strain and the consistency parameter are global degrees of freedom in the resulting spatially discrete problem. The ensuing proliferation of global degrees of freedom in the multifield approach is addressed by exploiting the block sparse structure of the algebraic system together with a tailored block matrix solver which can utilise emerging hardware architectures. A series of numerical problems demonstrate the validity, capability and efficiency of the proposed approach

Presentation at 1st GCEC Seminar. Overview of research on adaptation and fracture of 3rd metacarpal bone.

<p>This presentation contains an overview of the progress in PhD research titled: Investigation of bone adaptation to exercise and fracture in Thoroughbred racehorses.</p