Adaptive Gradient Elasticity and Mechanical Stimulation in Bone Remodelling

在当今人口老龄化的情况下，与骨丢失相关的问题正在增加。因此，它是至关重要的公共健康和福祉，一般提供一个战略，可以扭转骨degradation.Computational建模策略，需要补充和加强最近开发的治疗骨退化，即使用低幅度的机械振动，以触发骨再生。随后将使用计算机建模来优化个体患者的治疗。该项目是工程学（“机械振动”）和生物医学科学（“骨再生”）之间的跨学科，需要强大的数学建模输入，以补充现有的实验生物医学方案。骨降解是一种普遍现象，通常会导致骨折。骨退化有各种原因，其中最突出的是骨质疏松症，骨癌和常见的衰老。某些群体的个体特别容易发生骨降解，例如绝经后妇女。扭转骨退化已被世界各地的领先医学专家公认为对公共健康和公众福祉至关重要。可以通过药物措施刺激骨再生;然而，其长期影响仍未明确，可能存在不良副作用。最近，研究工作已经指向通过机械刺激触发骨再生。特别是动态负荷（与静态负荷相反）有利于刺激骨生长，即通过使患者反复地（例如每天20分钟，持续一年）暴露于日常活动（例如站立）的强度的应变。不幸的是，实验方案昂贵并且需要大量的组织和研究工作。通常还需要获得相关专业机构或道德委员会的批准。在许多工程领域，计算机建模可以用来补充和/或部分取代昂贵的实验方案。它被认为是适当的，建议在本研究中的计算机建模技术，可用于模拟骨重建由于振动机械刺激，从而考虑到通过多尺度方法的骨材料的微观结构。建议使用放大技术，并将这些微观结构的响应转化为宏观层面上的有效属性。由此产生的模型使用起来将相对简单，而且比相关的微观结构模型“透明”得多;因此，受益者使用这些模型应更加直接。在本研究中，一种特殊类型的多尺度技术，自适应梯度弹性模型，将被开发，以利于后续的应用。最后，骨刺激的依赖性的各个方面的机械振动，如频率，振幅和持续时间将进行分析。对这些方面的部分敏感性可以量化，随后用于操纵机械振动的细节，以优化骨生长和合理化患者治疗。

In nowadays ageing population, the problems related to bone loss are on the rise. As such it is of crucial importance to the public health and well-being in general to offer a strategy that can reverse bone degradation.Computational modelling strategies are needed to complement and enhance a recently developed treatment for bone degradation, namely using mechanical vibrations of low magnitude to trigger bone regrowth. The computer modelling will subsequently be used to optimise this treatment for individual patients. The project is interdisciplinary between Engineering ("mechanical vibrations") and Biomedical Sciences ("bone regrowth") and it requires strong mathematical modelling input to complement the existing experimental biomedical programme.The degradation of bone is a widespread phenomenon that is often followed by fracture. Bone degradation has various causes, most prominent of which are osteoporosis, bone cancer and common ageing. Certain groups of individuals are particularly prone to bone degradation, such as post-menopausal women. Reversing bone degradation has been recognised by leading medical specialists around the world to be of crucial importance to public health and public well-being. Bone regrowth can be stimulated by pharmaceutical measures; however, their long-term effects remain unspecified and there may be undesired side effects. More recently, research efforts have been directed towards triggering bone regrowth through mechanical stimulation. Especially dynamic loading (as opposed to static loading) is advantageous to stimulate bone growth namely through exposing the patient repeatedly (say 20 minutes per day for the duration of a year) to straining of the intensity of everyday activities such as standing.Unfortunately, the experimental programmes are expensive and require a lot of organisation and research efforts. It is also often necessary to acquire approval of the relevant Professional Institutions or Ethical Committees. As in many areas of engineering, computer modelling can be used to complement and/or partially replace the expensive experimental programmes. It is thought to be opportune to suggest in the present research computer modelling techniques that can be used to simulate bone remodelling due to vibrationary mechanical stimulation, thereby taking into account the microstructure of the bone material via a multi-scale approach. It is suggested to use upscaling techniques and translate these microstructural responses into effective properties on the macro-scopic level. The resulting models would be relatively simple to use and much more "transparent" than the associated microstructural models; thus, their use by the beneficiaries should be much more straightforward. In this research, a particular type of multi-scale techniques, adaptive gradient elasticity model, will be developed for the benefit of subsequent applications.Finally the dependence of bone stimulation on the various aspects of the mechanical vibration, such as frequency, amplitude and duration will be analysed. The partial sensitivities to these aspects can be quantified and subsequently used to manipulate the details of the mechanical vibrations in order to optimise bone growth and rationalising patient treatment.