Somethings About Biological Prostheses

Finite element models of the female biofidel were developed using a specific combination of segmentation with computed tomography and solid modeling tools capable of representing bone physiology and structural behavior. This biofidel finite element (FEM) model is used to evaluate the change in the physiological distribution of stress in the femoral prosthesis and to evaluate the new design criteria for biopsy. Biomimetics, biomechanics, and tissue engineering are three multidisciplinary fields that have been considered in this research to achieve the goal of improving the reliability of prosthetic implants. The authors took these studies to gather the untapped potential of such advanced materials and design technologies by developing finite models of Biofidel elements capable of correctly mimicking the biomechanical behavior of the femur. The new remodeling of the tetrahedral elements was performed in 3Matic looking for the congruence of the node at the bone-implant interfaces, where the material was defined for the new configuration of the finite elements. The evaluation of the mechanical properties was made taking into account the mechanical characteristics of the cortical and trabecular bone. For biomechanical integration of the implant, a custom material with an improved combination of strength and rigidity that matches the bone should be used. This greater biomechanical compatibility will avoid weakening the implant and increase lifespan, avoiding additional surgery for revision and allowing good biological integration (bone growth). Innovative biomimetic materials for tissue engineering based on hydrophilic polymers were developed by our research group and presented attractive physical, biological, and mechanical properties for biomedical applications. For use with metal prostheses, the authors have developed a hybrid biocompatible material, extremely biocompatible, based on hydrophilic chemicals and hydroxy-ethyl-methacrylate type. The structural metal composition of the new prostheses will be made of titanium alloys using additive technology based on melting thin layers of titanium powder (about 50 microns) on each other until the desired component is obtained (sandwich method). Then, the biomaterial and osteoconductive nanostructured material developed in our previous studies can cover the titanium structural prosthetic skeleton. These hybrid biological prostheses, which are made using synthetic materials capable of inducing the growth of biological networks and structural steel scaffolding, may favor the emergence of new classes of orthopedic hybrids in the medical field. The new hybrid bio-prosthesis could drastically reduce protection against stress while providing an advantageous improvement in the life of the prosthesis compared to traditional solutions. Recovering optimal joint functionality will improve the patient's quality of life, which perceives a significant reduction in the risk of the new surgery. The requirement to predict potential structural changes that could be induced by improper use of biologically compatible prostheses in bone structure and morphology has forced our studies to evaluate fictitious models that could be considered for efficient bone distribution and orthotropic behavior

Can a continuous mineral foam explain the stiffening of aged bone tissue? A micromechanical approach to mineral fusion in musculoskeletal tissues

Recent experimental data revealed a stiffening of aged cortical bone tissue, which could not be explained by common multiscale elastic material models. We explain this data by incorporating the role of mineral fusion via a new hierarchical modeling approach exploiting the asymptotic (periodic) homogenization (AH) technique for three-dimensional linear elastic composites. We quantify for the first time the stiffening that is obtained by considering a fused mineral structure in a softer matrix in comparison with a composite having non-fused cubic mineral inclusions. We integrate the AH approach in the Eshelby-based hierarchical mineralized turkey leg tendon model (Tiburtius et al 2014 Biomech. Model. Mechanobiol. 13 1003–23), which can be considered as a base for musculoskeletal mineralized tissue modeling. We model the finest scale compartments, i.e. the extrafibrillar space and the mineralized collagen fibril, by replacing the self-consistent scheme with our AH approach. This way, we perform a parametric analysis at increasing mineral volume fraction, by varying the amount of mineral that is fusing in the axial and transverse tissue directions in both compartments. Our effective stiffness results are in good agreement with those reported for aged human radius and support the argument that the axial stiffening in aged bone tissue is caused by the formation of a continuous mineral foam. Moreover, the proposed theoretical and computational approach supports the design of biomimetic materials which require an overall composite stiffening without increasing the amount of the reinforcing material

Bio-inspired design for engineering applications: empirical and finite element studies of biomechanically adapted porous bone architectures

Includes bibliographical references.2020 Summer.Trabecular bone is a porous, lightweight material structure found in the bones of mammals, birds, and reptiles. Trabecular bone continually remodels itself to maintain lightweight, mechanical competence, and to repair accumulated damage. The remodeling process can adjust trabecular bone architecture to meet the changing mechanical demands of a bone due to changes in physical activity such as running, walking, etc. It has previously been suggested that bone adapted to extreme mechanical environments, with unique trabecular architectures, could have implications for various bioinspired engineering applications. The present study investigated porous bone architecture for two examples of extreme mechanical loading. Dinosaurs were exceptionally large animals whose body mass placed massive gravitational loads on their skeleton. Previous studies investigated dinosaurian bone strength and biomechanics, but the relationships between dinosaurian trabecular bone architecture and mechanical behavior has not been studied. In this study, trabecular bone samples from the distal femur and proximal tibia of dinosaurs ranging in body mass from 23-8,000 kg were investigated. The trabecular architecture was quantified from micro-computed tomography scans and allometric scaling relationships were used to determine how the trabecular bone architectural indices changed with body mass. Trabecular bone mechanical behavior was investigated by finite element modeling. It was found that dinosaurian trabecular bone volume fraction is positively correlated with body mass like what is observed for extant mammalian species, while trabecular spacing, number, and connectivity density in dinosaurs is negatively correlated with body mass, exhibiting opposite behavior from extant mammals. Furthermore, it was found that trabecular bone apparent modulus is positively correlated with body mass in dinosaurian species, while no correlation was observed for mammalian species. Additionally, trabecular bone tensile and compressive principal strains were not correlated with body mass in mammalian or dinosaurian species. Trabecular bone apparent modulus was positively correlated with trabecular spacing in mammals and positively correlated with connectivity density in dinosaurs, but these differential architectural effects on trabecular bone apparent modulus limit average trabecular bone tissue strains to below 3,000 microstrain for estimated high levels of physiological loading in both mammals and dinosaurs. Rocky Mountain bighorn sheep rams (Ovis canadensis canadensis) routinely conduct intraspecific combat where high energy cranial impacts are experienced. Previous studies have estimated cranial impact forces up to 3,400 N and yet the rams observationally experience no long-term damage. Prior finite element studies of bighorn sheep ramming have shown that the horn reduces brain cavity translational accelerations and the bony horncore stores 3x more strain energy than the horn during impact. These previous findings have yet to be applied to applications where impact force reduction is needed, such as helmets and athletic footwear. In this study, the velar architecture was mimicked and tested to determine suitability as novel material architecture for running shoe midsoles. It was found that velar bone mimics reduce impact force (p < 0.001) and higher energy storage during impact (p < 0.001) and compression (p < 0.001) as compared to traditional midsole architectures. Furthermore, a quadratic relationship (p < 0.001) was discovered between impact force and stiffness in the velar bone mimics. These findings have implications for the design of novel material architectures with optimal stiffness for minimizing impact force

Микроструктурна адаптација коштаног ткива фацијалног скелета на дистрибуцију оклузалног оптерећења код особа са пуним зубним низом и њена улога у настанку прелома фацијалног скелета

Occlusal forces have traditionally been explained to transfer through the facial skeleton along specific osseous trajectories known as buttresses. These regions were assumed as zones of strength due to their thick cortical bone structure, while the areas between the buttresses containing thin cortical bone were considered weak and fragile. However, recent studies revealed that both cortical and trabecular bone of the mid-facial skeleton of dentulous individuals exhibit remarkable regional variations in structure and elastic properties. These variations have been frequently suggested to result from the different involvement of cortical and trabecular bone in the transfer of occlusal forces, although there has been no study to link bone microarchitecture to the occlusal loading. Moreover, although the classical concept of buttresses has been extensively studied by mechanical methods, such as finite element (FE) analysis, there is still no direct evidence for occlusal load distribution through the cortical and trabecular bone compartments individually. Additionally, relatively less scientific attention has been paid to the investigation of bone structure along Le Fort fracture lines that have traditionally been assumed as weak areas at which the mid-facial skeleton commonly fractures after injury. Papers published so far in this field focused mainly on the epidemiology and the role of injury mechanism in the fracture development, without considering the structural basis of increased bone fragility along the Le Fort fracture lines...Према традиционалном објашњeњу, пренос оклузалног оптерећења кроз кости лица током жвакања обавља се дуж специфичних путања унутар кости званих трајекторије или „батреси“. Ови делови костију лица сматрани су јаким зонама јер их изграђује кортикална кост велике дебљине, док су делови кости смештени између трајекторија сматрани слабим и фрагилним због њихове танке кортикалне грађе. Међутим, недавним истраживањима је откривено да и кортикална и трабекуларна кост средњег масива лица код особа са пуним зубним низом показују значајне регионалне варијације у грађи и еластичним својствима. Ове се варијације често сматрају адаптацијом кортикалне и трабекуларне кости на различито оптерећење у преносу оклузалних сила током жвакања, иако повезаност микроархитектуре кости и оклузалног оптерећења до сада није испитивана код људи. Штавише, иако је класични концепт преноса оклузалног оптерећења дуж трајекторија интензивно проучаван механичким методама, као што је метод коначних елемената, још увек није испитано на који начин се оклузалне силе преносе појединачно кроз кортикалну и трабекуларну кост. Значајно мању научну пажњу је привлачило испитивање грађе костију лица дуж Le Fort линија које су традиционално сматране најчешћим местима прелома костију фацијалног скелета узрокованих механичким силама. Досадашње студије у овој области су биле фокусиране углавном на епидемиолошка истраживања и улогу механизма повреде у настанку ових прелома, док структурна основа повећане фрагилности кости дуж Le Fort линија није испитивана..

High-Resolution Cone-Beam Computed Tomography is a Fast and Promising Technique to Quantify Bone Microstructure and Mechanics of the Distal Radius

Obtaining high-resolution scans of bones and joints for clinical applications is challenging. HR-pQCT is considered the best technology to acquire high-resolution images of the peripheral skeleton in vivo, but a breakthrough for widespread clinical applications is still lacking. Recently, we showed on trapezia that CBCT is a promising alternative providing a larger FOV at a shorter scanning time. The goals of this study were to evaluate the accuracy of CBCT in quantifying trabecular bone microstructural and predicted mechanical parameters of the distal radius, the most often investigated skeletal site with HR-pQCT, and to compare it with HR-pQCT. Nineteen radii were scanned with four scanners: (1) HR-pQCT (XtremeCT, Scanco Medical AG, @ (voxel size) 82 mu m), (2) HR-pQCT (XtremeCT-II, Scanco, @60.7 mu m), (3) CBCT (NewTom 5G, Cefla, @75 mu m) reconstructed and segmented using in-house developed software and (4) microCT (VivaCT40, Scanco, @19 mu m-gold standard). The following parameters were evaluated: predicted stiffness, strength, bone volume fraction (BV/TV) and trabecular thickness (Tb.Th), separation (Tb.Sp) and number (Tb.N). The overall accuracy of CBCT with in-house optimized algorithms in quantifying bone microstructural parameters was comparable (R-2 = 0.79) to XtremeCT (R-2 = 0.76) and slightly worse than XtremeCT-II (R-2 = 0.86) which were both processed with the standard manufacturer's technique. CBCT had higher accuracy for BV/TV and Tb.Th but lower for Tb.Sp and Tb.N compared to XtremeCT. Regarding the mechanical parameters, all scanners had high accuracy (R-2 >= 0.96). While HR-pQCT is optimized for research, the fast scanning time and good accuracy renders CBCT a promising technique for high-resolution clinical scanning

Validity and sensitivity of a human cranial finite element model: Implications for comparative studies of biting performance

Finite element analysis (FEA) is a modelling technique increasingly used in anatomical studies investigating skeletal form and function. In the case of the cranium this approach has been applied to both living and fossil taxa to (for example) investigate how form relates to function or infer diet or behaviour. However, FE models of complex musculoskeletal structures always rely on simplified representations because it is impossible completely to image and represent every detail of skeletal morphology, variations in material properties and the complexities of loading at all spatial and temporal scales. The effects of necessary simplifications merit investigation. To this end, this study focuses on one aspect, model geometry, which is particularly pertinent to fossil material where taphonomic processes often destroy the finer details of anatomy or in models built from clinical CTs where the resolution is limited and anatomical details are lost. We manipulated the details of a finite element (FE) model of an adult human male cranium and examined the impact on model performance. First, using digital speckle interferometry, we directly measured strains from the infraorbital region and frontal process of the maxilla of the physical cranium under simplified loading conditions, simulating incisor biting. These measured strains were then compared with predicted values from FE models with simplified geometries that included modifications to model resolution, and how cancellous bone and the thin bones of the circum-nasal and maxillary regions were represented. Distributions of regions of relatively high and low principal strains and principal strain vector magnitudes and directions, predicted by the most detailed FE model, are generally similar to those achieved in vitro. Representing cancellous bone as solid cortical bone lowers strain magnitudes substantially but the mode of deformation of the FE model is relatively constant. In contrast, omitting thin plates of bone in the circum-nasal region affects both mode and magnitude of deformation. Our findings provide a useful frame of reference with regard to the effects of simplifications on the performance of FE models of the cranium and call for caution in the interpretation and comparison of FEA results