3rd ed. 10, 911 s.
- Conspectus
- Knihovnictví. Informatika
- NML Fields
- lékařská informatika
- knihovnictví, informační věda a muzeologie
This study focuses on the drop foot case related to hyperthyroidism of the ankle joint resulting in the relaxation of the toes during walking. This condition requires treatment using an ankle-foot orthosis. Traditional orthosis techniques lack precision and depend on the skill of the fabricator. This research aims to make a bias in ankle-foot orthosis design and analysis methods, where a complete methodology of numerical design and testing has been proposed using advanced engineering software. A numerical model of the patient's foot was generated and used to design an ankle-foot orthosis model using SolidWorks. The designed model was mechanically analyzed by the finite element method using ANSYS Workbench 16.1 under different static and dynamic loading conditions. The ankle-foot orthosis model was numerically designed and analyzed before the manufacturing process. This is believed to reduce time and material loss and foster the use of numerical models in biomedical applications. This study suggests focusing on the design and analysis of orthoses according to the patient's measurements. This is expected to increase the comfort and raise the level of treatment. Numerical design methods also enable precise manufacturing using computerized devices such as three-dimensional printers.
- MeSH
- Finite Element Analysis MeSH
- Biomechanical Phenomena MeSH
- Walking physiology MeSH
- Computer-Aided Design MeSH
- Equipment Design methods MeSH
- Ankle Joint physiology MeSH
- Humans MeSH
- Gait Disorders, Neurologic * etiology physiopathology therapy MeSH
- Foot Orthoses * MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
Computational fluid dynamics (CFD) has grown as a tool to help understand the hemodynamic properties related to the rupture of cerebral aneurysms. Few of these studies deal specifically with aneurysm growth and most only use a single time instance within the aneurysm growth history. The present retrospective study investigated four patient-specific aneurysms, once at initial diagnosis and then at follow-up, to analyze hemodynamic and morphological changes. Aneurysm geometries were segmented via the medical image processing software Mimics. The geometries were meshed and a computational fluid dynamics (CFD) analysis was performed using ANSYS. Results showed that major geometry bulk growth occurred in areas of low wall shear stress (WSS). Wall shape remodeling near neck impingement regions occurred in areas with large gradients of WSS and oscillatory shear index. This study found that growth occurred in areas where low WSS was accompanied by high velocity gradients between the aneurysm wall and large swirling flow structures. A new finding was that all cases showed an increase in kinetic energy from the first time point to the second, and this change in kinetic energy seems correlated to the change in aneurysm volume.
- Publication type
- Journal Article MeSH
Frozen aqueous solutions are an important subject of study in numerous scientific branches including the pharmaceutical and food industry, atmospheric chemistry, biology, and medicine. Here, we present an advanced environmental scanning electron microscope methodology for research of ice samples at environmentally relevant subzero temperatures, thus under conditions in which it is extremely challenging to maintain the thermodynamic equilibrium of the specimen. The methodology opens possibilities to observe intact ice samples at close to natural conditions. Based on the results of ANSYS software simulations of the surface temperature of a frozen sample, and knowledge of the partial pressure of water vapor in the gas mixture near the sample, we monitored static ice samples over several minutes. We also discuss possible artifacts that can arise from unwanted surface ice formation on, or ice sublimation from, the sample, as a consequence of shifting conditions away from thermodynamic equilibrium in the specimen chamber. To demonstrate the applicability of the methodology, we characterized how the true morphology of ice spheres containing salt changed upon aging and the morphology of ice spheres containing bovine serum albumin. After combining static observations with the dynamic process of ice sublimation from the sample, we can attain images with nanometer resolution.
Dental implant dimensions, and bone quality and quantity play a key role in early osseointegration and long-term prognosis in posterior edentulous maxilla. Treatment with short implants, preferably in a bicortical manner, is an accepted modality; however, short implants have limitations leading to increased stress concentrations in alveolar bone, potential overload and implant failure. Implant models of 3.3, 4.1, 4.8 and 5.4 mm diameter and 4.5, 5.5, 6.5, 7.5 and 8.5 mm length were placed in posterior maxilla 3-D models with corresponding residual bone heights. Bone-implant assemblies were analyzed in finite element software ANSYS 15. All materials were assumed to be linearly elastic and isotropic. 118.2 N oblique loading was applied to investigate stress distributions in bone tissues. The concept of ultimate functional load (UFL) was selected as a criterion to compare load-carrying capacity of implants and to evaluate the influence of available bone height and implant dimensions on load-carrying capacity. For all implants, UFL was calculated by limiting von Mises stresses in cortical or cancellous bone with bone strength (100 MPa for cortical and 2 MPa for cancellous bone). Implant load-carrying capacity depends on diameter and available bone height. Wide implants have higher load-carrying capacity than narrow implants. Short implants with proper diameter and length avoid bone overstress, even in Type IV bone.
- MeSH
- Finite Element Analysis * MeSH
- Humans MeSH
- Maxilla * physiology MeSH
- Osseointegration MeSH
- Materials Testing * MeSH
- Weight-Bearing MeSH
- Dental Implants * MeSH
- Dental Prosthesis Design MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
Background: Hip fractures are a major cause for disability in patients. They require immediate attention as they could otherwise cause death. Hip fractures are almost always treated with surgery by implantation. Implants are of various types accounting for the many variations in hip fractures. Objectives: This paper presents the design and analysis of a hip implant using Finite element analysis. Fracture conditions are determined and the optimal design of the implant is obtained for improving healthcare and patient safety. Methods: Anthropometric parameters of the human femur bone are collected from a particular age group. These are then used to obtain a CAD model of the bone using CATIA. The standard Charnley hip implant, used in total hip replacement surgery is also modeled. The proposed models are analyzed using ANSYS software by assigning appropriate material properties to the bone and implant. The stress distribution is observed when loads corresponding to normal gait conditions are applied. The load at which fracture occurs is then determined experimentally. Results: Based on the analysis results of the modeled bone, the implant is optimized by varying the base cross section, the bio-materials used, and the design parameters so that, its stress response mimics that of the actual bone. It is found that the model no 2 as in Table 6 with head diameter 28mm, neck diameter 10mm, neck angle 128 degrees has minimum strain at the neck region with a value of 0.65 and is found to be suitable for implant design. Results show that initiation of fracture in the implant occurs at 2000N and complete fracture occurs at 2400N. Conclusions: The 3D models are very useful in simulation of bone fractures and internal fixations with implants. In this work, the hip joint and implant model, developed in CATIA software, help to understand how these structures adapt to external forces disturbances [15]. This will help the doctors to chose the optimal implant for a particular patient. This leads to greater accuracy and patient specificity.
- MeSH
- Anthropometry methods MeSH
- Hip Fractures * surgery therapy MeSH
- Humans MeSH
- Musculoskeletal System * anatomy & histology surgery injuries MeSH
- Orthopedic Procedures methods instrumentation trends MeSH
- Computers MeSH
- Prostheses and Implants * MeSH
- Statistics as Topic MeSH
- Imaging, Three-Dimensional * methods instrumentation utilization MeSH
- Check Tag
- Humans MeSH
The mid-term longevity of femoral components varies considerably, with some showing failure due to early aseptic loosening. Since the hip joint is subject to heavy mechanical loads, it can be assumed that the mechanical interaction of the implant, bone cement and femur will play a key role in the resultant reliability of an arthroplasty. This study was designed to examine this mechanical interaction in four femoral components different in construction (Poldi-Cech, CF-30, MS-30 and PFC) using mathematical simulation. MATERIAL AND METHODS Four stem/cement/femur 3-D mathematical models, comparable in quality, infolving the Poldi-Cech, CF-30, MS-30 and PFC stems, respectively, were constructed. A 3-D model for each stem was created according to its real, middle-size femoral component. Each 3-D model of the cement mantle corresponded in shape to the mantle of the appropriate real stem, with its thickness based on the recommended values of 4-7 mm in the proximal and 1-3 mm in the distal part, and with the cement mantle reaching as far as 10 mm distal to the femoral stem tip. For simplicitys sake the outer surface of the cement mantle was simulated as smooth. A 3-D model involving the proximal epiphysis and the metaphysis of a femur was reconstructed, based on a series of CT cross-sections obtained periodically at 10.5-mm and 2.5-mm distances. The sten/cement/femur model with the MS-30 stem also included a centraliser. The mechanical interaction of the stem, bone cement and bone tissue was examined by means of mathematical stimulation using ANSYS 5.7 software based on finite element analysis. RESULTS For the sake of simplicity, only two key parameters are presented, namely, contact stress at the stem-cement interface and equivalent deformation in the stem/cement/femur system. The least satisfactory stress loading was in the CF-30 stem whose sharp edges showed the values of contact stress about six-times higher than on the mid-medial portion of the stem, with the sharp edges behaving as stress concentrators. A satisfactory stress loading was found in Poldi-Cech, MS-30 and PFC stems, in which contact stress was evenly distributed along the whole lenght of the stem and the values at the edges and on the midmedial portion did not differ much. DISCUSSION The distribution of contact stress is one of the most important factors for the long-term longevity of implants. It was found least satisfactory in the CF-30 stem whose sharp edges act as stress condenser adversely affecting not only the stemcement interface, but also the resultant stress distribution within the femur. The most satisfactory results of stress distribution were recorded in the Poldi-Cech and MS-30 stems. The PFC stem also responded satisfactorily to the simulated stress loading. However, on loading whose substantial part would be torsion, the stems circular or oval cross-section could interfere with rotation stability of the implant; but this was impossible to detect by the mathematical simulation used in this study. CONCLUSIONS The results presented here show that, in the Poldi-Cech, CF-30, MS-30 and PFC femoral stems, a good agreement was achieved between the results of their clinical application and those of mathematical modelling of their mechanical properties. It can be concluded that mechanical interaction among the femoral stem, cement mantle and bone tissue plays the key role in the long-term longevity of such an implant. Key words: Poldi-Cech, CF-30, MS-30, PFC, mechanical interaction, contact stress.
- MeSH
- Femur MeSH
- Bone Cements MeSH
- Hip Prosthesis MeSH
- Humans MeSH
- Stress, Mechanical MeSH
- Computer Simulation MeSH
- Check Tag
- Humans MeSH
