Papers by Keyword: Hip Implant

Abstract: Additive manufacturing has significantly advanced in the last two decades and can now produce various mechanical components. However, some limitations exist, such as the size and surface finish of the part. This work reports preliminary results of joining dissimilar metals or alloys by additive manufacturing inspired by welding dissimilar joints. Single laser tracks were produced by laser surface alloying, simulating laser powder bed fusion, using homemade additive manufacturing equipment composed of a computer numerically controlled table and a ytterbium-doped fiber laser operating inside an Argon chamber. Mo, Co, and Cr powders were used to obtain additively manufactured layers on a Ti substrate, aiming to produce a gradient from the Ti to the Co-Cr-Mo alloy. The results showed that increasing the heat input increased the dilution of Ti in the Co-Cr-Mo modified layer and decreased the hardness and the formation of cracks. Obtaining an intermediate layer of Mo reduced the dilution in the upper layers. It increased hardness by 629 ± 20 HV, indicating the feasibility of manufacturing multi-material pieces made of commercially pure Ti with an intermediate layer in Mo and a Co-Cr-Mo alloy. Such pieces aim for future application in hip implants, in which, in addition to the more flexible Ti stem, a femoral head with properties close to the Co-Cr-Mo alloy for excellent wear resistance.

Abstract: The hip is one in every of the various joint at intervals the body. The correct operating of this joint is essential. For the aim once the hip is injured whole, a substitution procedure of the entire joint ought to be done to reinstate its operating, that is known as absolute hip surgical process. It is finished with the assistance of inserts of various biomaterials, as an example, polymers, metals, and pottery. The primary issues with regard to the utilization of various biomaterials are the reaction of the body's instrument to wear trash. Throughout this audit, biomaterials that are developing is talked regarding aboard the wear and tear and tear conduct and instrument. To boot, the numerous properties of the biomaterials are talked regarding aboard the expected preferences and drawbacks of their utilization. Further, the blends of various biomaterials at intervals the articulating surfaces are cleft and so the problems regarding their utilization are assessed. This paper hopes to passes away an in depth review of the trauma fringe of bearing surfaces of hip prosthetic devices. Additionally, this paper can offer AN ordered blueprint of the materials nearby their favorable circumstances and detriments and besides the conceivable outcomes of use. Keywords: - Hip implant; Biomaterials; Wear mechanism; Bearing surfaces; Polymers

Abstract: Titanium and its alloys, especially Ti-6Al-4V have found application as hip implants due to their mechanical properties, excellent biocompatibility, and corrosion resistance. The use of cementless hip implants has increased over the years as it is thought that this type is more durable compared to cemented hip implants. Cementless hip implants have a porous surface that allows the bone to grow into it and form a strong bone–implant connection. The goal of this study is the use of Finite Element Method simulations to obtain information about how different types of surface topography of a TI-6Al-4V hip implant affect the shear stress, which is used to access the bone-implant connection. Finite Element Analysis is used to analyze the stress distribution in three simple surface modifications in a hip implant under different types of loads. The optimal surface modification out of these three is obtained based on the shear stress distribution, as it is known that lower shear stress promotes bone ingrowth. In this study, we have considered the interaction between cortical bone and implant surface. Material properties and boundary conditions used for the simulations have been adapted from literature.

Abstract: Wear is a problem for metal on polymer (MOP) hip implants to perform lifetime endurance. Polymer excessive volumetric loss leads to implant failures. Attempts to solve this problem are usually initiated with tribological tests. The method is time-consuming because the sliding speed is low. There is a faster way to use a computational method to gather wear data. This research aims to investigate the numerical convergence of predicted wear volume with the finite element method (FEM). The model is a commercially pure titanium (cp Ti) and ultra-high molecular weight polyethylene (UHMWPE) MOP hip implant. A dynamic Paul physiological load was applied to the model. Volumetric loss of the polymer was calculated with a wear equation involved nonlinear contact load and contact area. The inputs of calculation are wear factor and the computational contact mechanic performed by FEM. The wear factor was obtained by performing biotribological experiments with a multidirectional pin on disc tribotest. Predicted wear volume was validated with hip simulator experimental data from the literature. Convergences were found at the mesh density of 1.38 elements/mm³. An acceptable numerical error was obtained in the model with 1 mm element size for femoral head and 0.3 mm for acetabular cup. This model was then used for the investigation of load increment effects. The result is that load increment variations do not affect wear volume and contact mechanic numerical outputs. The calculated stresses are below the UHMWPE yield stress limit. In this elastic region, the effects of strain rate caused by load increment are negligible.

Abstract: This study aims to develop dedicated computer-aided workpiece positioning system for biomedical application. The application is for machining micropits on spherical surface of hip implant using electrical discharge machining (EDM). New spherical positioning system has been designed and realized for further development. A computer is used as a main control unit to control the positioning system and modular servo motors with tuneable PID controller are utilized by the system. This paper explains the configuration of the implemented system and tuning process to optimize the system performance.

Abstract: Oil pocket has been reported that it may improve tribology characteristic and thus prolong the lifespan of the joint. In order to implement it on spherical surface, appropriate positioning system is required. This paper reports the investigation of three axes workpiece positioning system in order to machine oil pocket (micro-pits) on hip implant. A conventional linear x-y-z axes configuration (Cartesian coordinate) and two configuration of spherical coordinate (swing-swing and swing-rotate configuration) are applied in simulation. All machined workpiece are investigated in pits distribution, shape, and machined angle. The inspection concludes that spherical method with swing-rotate configuration is the most suitable method for machining oil pocket on spherical surface.

Abstract: This research investigates the stress distribution of the three types of implanted femurs using the finite element method analysis. The comparisons of the stress distribution between the implanted femursand the healthy femur were performed and the characteristics in the stress shielding of each casewere clarified. Since the load is transferred on the contact surface between the implant and the inner surface of the femur in the case of the total hip arthroplasty, the stress in the intertrochanteric zone (Gruen zone 7) become very small, and the phenomenon of the stress shielding is confirmed obviously. The stress distributions of the femurs afterthe resurfacing hiparthroplasty and the thrust plate prosthesis are about the same with that of the healthy femur, so, the possibility of the stress shielding is considered lower compared with the femur after the total hip arthroplasty. However, considering the stress concentration thatwill increase the risk of femoral fracture caused by the screws for the fixation of the implant in the thrust plate prosthesis, the resurfacing hiparthroplastymay beconcluded as the best method among these three types of implants to avoid stress shielding.

Abstract: The quantity and quality of regenerated bone strongly depends on the direction and amplitude of in vivo principal stress; therefore, in vivo stress distribution near bone implants should be optimized on the basis of the morphology of the interface between an implant and bone tissue. In this study, grooves were created on the implant surface in order to improve the surface morphology of the implant for optimizing in vivo stress distribution near the implant. The preferential alignment of the biological apatite (BAp) c-axis, which is a parameter of bone quality and controls the mechanical function of bones, is closely related to stress distribution; therefore, the direction of principal stress should be matched with the direction of the groove on the implant surface. Hip implants were prepared with grooves aligned at different angles from the surface; the grooves were located on the stem portion. These implants were inserted in a beagle femur to investigate the dependency of the quantity and quality of newly formed bone in the grooves on the groove angle. The degree of preferential alignment of the BAp c-axis of the regenerated bone in the grooves strongly depends on the angle of the groove to the principal stress vector that was estimated previously to an animal experiment. The regenerated bone forms anisotropic BAp orientation in response to the principal stress in the grooves; therefore, the direction of the grooves has to be designed on the basis of the stress distribution near the implant.

Abstract: Amid increasing numbers of artificial joint implantation surgeries, improving the quality of life (QOL) for patients by accounting for individual variation is a primary concern. Thus, we aim to develop implants designed to optimize the interface between implant and living bone. In particular, for ensuring long-term durability and stability after implantation, we focused on inducement of appropriate alignment for biological apatite (BAp) crystallites and the related collagen (Col) fibers as a bone quality parameter. In this study, we predicted that when stress is applied to bone, the BAp/Col preferential alignment can be formed on the basis of our previous result if osteocytes, which can sense its around stress field, are in an environment that is aligned with the principal stress vector. We tested this idea by introducing grooves with the different angles on the implant surface, considering the principal stress direction. This study finally analyses the effect of stress transmission by a load at the proximal femur on the bone inside and near the grooves by using a mechanical simulation in which groove angles and positions can be changed on the implant surface. Furthermore, we carried out animal experiments using a 2-years-old beagle to examine the effect of grooves in the principal stress direction on the surface in vivo. As a result, bone formation in grooves on the implant surface strongly depends on the grooved angle to the principal stress vector and the grooved position on implants. The new bone preferentially formed inside the grooves parallel to the principal stress direction predicted by three dimensional finite element analysis (FEA) in the proximal area of beagle femur.