Biomedical engineering advances最新文献

Background and Objective

Primary stability evaluation of screw implants through pull-out or push-in experiments is commonly used to investigate the mechanism of screw loosening. Numerical models simulating these testing methods could provide an enhanced understanding of the underlying attachment mechanisms as well as save time and cost in the development of new screws. However, previous numerical models have been limited by compromises between modelling the trabecular structure at high resolution versus incorporating sophisticated mechanical properties and boundary conditions, leading to overestimated mechanical performance. The aim of this study was to overcome these limitations.

Methods

We developed explicit models incorporating the microstructure of trabecular bone, with frictional contact, and a non-linear material model incorporating damage. One model digitally inserted the screw into the trabecular bone structure using Boolean operations, while another model simulated the screw's rotational insertion.

Results

The results showed a strong correlation between numerical and experimental results (R²: 0.54–0.93) for force-displacement response in terms of stiffness and strength. We found that the damage induced by the screw insertion process is an important factor to be considered, as the absence of modelling it led to an overestimated stiffness in previous studies.

Conclusions

The study highlights the importance of including frictional contact and also identified screw insertion damage as an important part of the simulating screw-bone interaction. Our findings demonstrate the potential of explicit finite element models for accurately replicating experimental push-in results and optimizing orthopaedic screws. The code is available at https://github.com/zhou436/Bone-Screw-Constructs-eFEM.

Amputations are a prominent affliction that occur worldwide, with causes ranging from congenital, disease-based, or external reasons such as trauma. Prosthesis provides the closest alternative functional replacement to the loss of a limb. Before any form of rehabilitation support can be offered to amputee patients, an assessment of their degree and level of mobility first needs to be evaluated using the K-level grading system. The typical means towards the assigning of a K-level grading is through qualitative methods, which have been criticized for being subjective and, at times, imprecise. As a means towards remedying this shortcoming, we investigated the prospect of utilizing data from wearable sensors for analyzing the stride pattern and cadence of various subjects towards the quantitative inference of a K-level. This was accomplished using data from accelerometers, alongside advanced signal processing and machine learning models, towards the quantitative identification and differentiation of the various K-levels of amputees of varied levels of mobility. The experimental results showed that this aim could be accomplished under the circumstance investigated and the models applied as part of this research. Additional analysis was also done on the use of data from accelerometers towards the differentiation between amputated and non-amputated subjects, which showed that the cohorts could be classified and differentiated using purely accelerometer data and the accompanying postprocessing methods.

Cells can be cultured to very high densities in hollow alginate tubes ($5-10\times {10}^{8}cells/mL),$ with the provisothat their nutrient and oxygen needs are met. After the tubes have been extruded, they are suspended in growth medium. Nutrients and metabolic products pass readily through the alginate tube walls and the cells grow from small aggregates until they fill the hollow space in the tube. A mathematical model is presented of nutrient and oxygen transport between the bulk phase and the tubes. Our main result is a necessary condition for growing cells to confluency. It sets an upper limit on the inner tube diameter. This limit depends on the alginate wall thickness, transport properties and consumption rates. Experimental results are reported for l-Wnt-3a cells, which have been expanded in tubes with inner diameters of $400,500,600$and $700\mu m$. For our experimental set-up, glucose was the limiting nutrient. Cells reached confluency in $400and500\mu m$ tubes at bulk glucose concentrations of $20mM$. When the bulk glucose concentration was increased to 25, 30 and 35 mM, confluency was reached in $600\mu m$ tubes for all three cases. Confluency was not achieved in tubes with inner diameters of 700 um, even at the elevated glucose concentrations, suggesting that the dissolved oxygen concentration has become the limiting factor. These results match the model predictions well and confirms that the model can be used to select tube dimensions.

Rhinoplasty is a popular surgical operation, so proposing trustworthy assessment methods is crucial. Previous studies often utilized traditional or non-automatic methods for rhinoplasty evaluation, overlooked the aesthetic harmony of the nose with other facial features, and provided limited descriptions of facial beauty without detailed explanations. To address these limitations, we have developed a deep learning-based system for quantitative and qualitative facial beauty assessment and rhinoplasty results based on the random preoperative and postoperative color photographs of 376 patients, differentiating male and female faces. The quantitative evaluation includes automatically extracting 3D facial key points from frontal and lateral views, developing a novel mathematical 3D facial model, applying seven criteria from rhinoplasty literature, and assigning related scores. The qualitative evaluation comprises the design of a questionnaire, the extraction of facial features using a unique CNN-based algorithm, and the assignment of scores based on the questionnaire's results. Our method calculates the success percentage of rhinoplasty and provides precise and comprehensive quantitative and qualitative beauty scores. The accuracy of the proposed facial feature extraction network is 71 %, which is considered acceptable according to the complexity of defining beauty and the novelty of this work. All procedures and outcomes are verified by an ENT (Ear, Nose, and Throat) specialist. In particular, based on the presented extensive tables and histograms, some patients have lower postoperative scores than preoperative ones in some instances, which caused negative success scores. For this reason, individuals' appearance may occasionally worsen following rhinoplasty instead of improving. Therefore, preoperative assessments of facial features are crucial, and our proposed system facilitates this process. Our research also impacts individual self-assessment and surgeons' awareness significantly.

A variety of methodologies have been applied for characterizing covalent immobilizations of biomolecules and other compounds on metal implant surfaces, due to the positive impact of functionalization and the enhancement of biomimetic signaling at covalently immobilized biomaterial surfaces. However, current challenges should be addressed, as both physically adsorbed and covalently immobilized molecules usually coexist on functionalized surfaces and covalent immobilization efficiencies greatly vary among works, in which the immobilized biomolecule size seems a determinant parameter of the efficiency.

Discrimination of the irreversible-bound covalent fraction should be assessed and advanced techniques for surface characterization must be conducted, such as quartz crystal microbalance or photon induced spectroscopy, as evaluation criteria. Verification of biomolecule activity once it is covalently immobilized on metal substrates is also required. Long-term stability and degradation resistances studies are also highly recommended for obtention of long-lasting, biomimetic-active surfaces upon covalent functionalization of metal biomaterials for medical applications.

The demand for designing an ideal bone substitute has emerged significantly to address the clinical limitations associated with the current bone grafting materials. A thorough understanding of the complex architecture and cellular composition of natural bone is crucial to design a biomimetic bone graft that closely emulates the physiological structure of the lost bone. There is a dire need for close collaboration among clinicians, nanotechnologists, and tissue engineers to design clinically relevant bone grafts that can promote efficient osteoconduction, osteogenesis and osteoinduction. Clinically, bone grafting procedures mainly involves the utilization of xenografts, allografts or autograft, a combination of natural and synthetic materials, polymer, metals and bioceramics. The advent of 3D printing techniques has revolutionized the field of bone tissue engineering. These additive manufacturing technologies utilizing digital design features and high precision enable researchers to replicate complex anatomical structures including bone. This review aims to present an overview of the determinants of an ideal bone graft, types of available bone grafting materials, and emphasizes the recent advancements in the field of regenerative medicine for designing biomimetic bone repairing scaffolds.

Nowadays, the dental implant surgery is a sophisticate and accurate sector with techniques increasingly innovative such as rapid prototyping, guided implant surgery and stem cell-based approaches. An example is certainly the use of multiple implants (4–6), instead of several prosthesis in case of human edentulous condition. The aim of this research is to investigate the mechanical behavior of the All-on-Four technique for different boundary conditions such as the value of load, framework material, type and position of implant. The goal was essentially trying to find out, by the application of structural static Finite Element Analysis (FEM), the best design for this specific treatment. After that, a stress-life fatigue numerical analysis was conducted for the optimal configuration in order to estimate the fatigue life in accordance with both Gerber and Goodman mean stress theory. The coupling involved the implants supported by an arch and a human mandible composed of cortical and cancellous part. After the simulations, it was found that the stress/strain field was very sensitive to the boundary conditions imposed. In particular, the position of the implants and the material framework yielded different responses depending on the implant design. Finally the use of ultrashort implants provided a significant decrease in the developed efforts than the long ones if the first premolar position was assumed. More specific, the stress peaks were in the range 100–225MPa for the implants, 300–537MPa for the framework, 50–124MPa for the cortical bone and 3–35MPa for the cancellous bone and they were located essentially in the abutment-framework connection as much as in implant neck-bone coupling. The best design saw the presence of ultra-short implant, first premolar position and Co-Cr alloy as framework material. The fatigue test confirmed the stability of the structure even with dynamic loads, but critical spots were present in the framework. In conclusion, the All-on-Four technique is a valid and safe alternative, even in case of ultrashort implants, for human edentulism care.

Damage to the dura mater may occur during intracranial or spinal surgeries, which can result in cerebrospinal fluid leakage and other potentially fatal physiological changes. As a result, biological and synthetic derived scaffolds are typically used to repair dura mater post intracranial or spinal surgeries. The extracellular matrix of xenogeneic dura scaffolds has been shown to exhibit increased cell infiltration and regeneration than synthetic dura materials. In this study, we investigated the biocompatibility of native and decellularized porcine dura by seeding rat fibroblast cells onto the constructs. Cell proliferation, cell viability, and the mechanical properties of these dural grafts were evaluated post-re-seeding on days 3,7 and 14. Live-dead staining and resazurin salts were used to quantify cell viability and cell proliferation, respectively. Micro indentation was conducted to quantify the mechanical integrity of the native and acellular dura graft. The findings indicate that the acellular porcine dura graft creates a beneficial setting for infiltrating rat fibroblast cells. Cell viability, proliferation, and micro indentation results on the acellular grafts are comparable with the native control porcine dura tissue. In conclusion, the porcine scaffold material showed increased cell viability at each time point evaluated. The sustained mechanical response and favorable viability of the cells on the decellularized grafts provide promising insight into the potential use of porcine dura in clinical cranial dura mater graft applications.

In recent years there has been a steady growth in the number of new robotic devices developed for surgical intervention. The market has rapidly grown into a multibillion-dollar industry. A significant number of commercial robots have been developed for several surgical procedures. Considering the recent developments in surgical robotics and its significant market potential we have studied the existing commercially available robotic surgical systems. The purpose of this review is to understand the current trends and existing gaps in this field to provide the developers with proper insight about the future direction. We reviewed the systems based on their target anatomical location and summarized the working principle for each robot, including their regulatory status.

A cerebral aneurysm is a medical disorder that occurs when the wall of the cerebral artery ruptures as a result of abnormally high blood pressure. The imaging techniques that are now in use, such as CT and MRI scans, can only show the geometrical information about an aneurysm and cannot determine the risk of rupture that relates to the progression of an aneurysm. In this work, computational modeling was performed to simulate aneurysm progression and to analyze the stress development for a variety of different pressure loading conditions. Image segmentation was utilized to segment one anterior cerebral artery and one anterior communicating artery, both of which were rebuilt to generate aneurysm models at susceptible locations of the aneurysm progression simulation. To represent the various phases of aneurysm development, five different aneurysm sizes with two varying wall thicknesses were identified. The diastolic pressure, the systolic pressure, and the hypertensive pressure were applied to simulate the actual pressure conditions for the anterior cerebral arteries. The rupture risk was determined by analyzing the stress distributions across all of the models. It was estimated that the stresses around the walls of aneurysm varies with an incremental change in both the diameter of the aneurysm and the magnitude of the blood pressure. Aneurysms that were observed to have significant rupture risks were those that had a large diameter and a thin wall and were simulated at high blood pressures. The findings of this research are anticipated to assist medical practitioners in estimating rupture risks with known imaging, based on the diameters of aneurysms, and in early decision making for the treatment of aneurysms.