Papers by Keyword: Total Hip Replacement

Abstract: Total Hip Replacement (THR) requires careful planning preparation, especially in the geometry suitability between the patient's bone and the implant. If it is applied incorrectly, it will be dangerous for the patient, such as the risk of complications, dislocation, and re-surgery. This paper aims to compare the size of the patient's THR geometry as a basis for consideration in implant designs to minimize the risk of harm after implantation. This study was limited to male patients only. The computed tomography scanning data (CT-Scan data) in the lower abdomen, segmented to hip joint area belonging to the American race and an Indonesian male, were compared. The comparison indicates that the American race data has a greater dimension than Indonesian. The American hip bone geometry result is following the standard modern implant by Johnson and Johnson size. By all analysis, the fittest geometry for the Indonesian male patient needs to adjust and has a smaller size than the commercial implant. This study finally recommends the specific length of the femoral stem for the optimal THR implant with the parameter values of Femoral Head Offset, Neck Length, Neck Shaft Angle, Mediolateral Width 1, Mediolateral Width 2, Mediolateral Width 3 respectively for the right THR, namely 37.9; 31.6; 134.3; 43.1; 13.62; 12.36; while the left THR is 38.9; 31.7; 134.5; 43.1; 13.70; 12.4 in mm. Overall, the precise implant planning based on real patient conditions and anthropometry is necessary to match implants and bone anatomy.

Abstract: Total hip replacement (THR) is a flourishing orthopaedic surgery which generating billion of dollars of revenue. The cost associated with the fabrication of implants has been increasing year by year and this phenomenon has burdened the patient with extra charges. Consequently, this study will focus on designing an accurate implant via implementing the reverse engineering of three dimensional morphological study based on a particular population. By using the finite element analysis, this study will assist to predict the outcome and could become a useful tool for pre-clinical testing of newly designed implant. A prototype is then fabricated using 316L stainless steel by applying investment casting techniques which reduce manufacturing cost without jeopardizing implant quality. The finite element analysis showed the maximum von Mises stress was 66.88 MPa proximally with a safety factor of 2.39 against endosteal fracture, and micromotion was 4.73 μm which promotes osseointegration. This method offers a fabrication process of cementless femoral stems with lower cost, subsequently helping patients, particularly those from non developed countries.

Abstract: The paper presents the processing technology that could be used in order to obtain a new design of a stem component for a hip prosthesis type lattice beam. This new design was made based on the analysis of the currently successful stems used in clinical practice and on different biomechanical and biomaterials criteria. Metallic biomaterials used for manufacturing different components for hip prosthesis are usually austenitic stainless steel type 316L, Co-Cr alloy and titanium based alloy. In our study, considering the specific design of the stem, stainless steel type 316L with the nominal compositions (%weight): C <0.03, Cr 17, Ni 14.5, Mo 2.7, Mn <2.0, Si <1.0, P <0.025, S <0.010, Fe balance is used. Different mechanical processing techniques were used in order to obtain the experimental prototype. According to the well-known limitation of the stainless steel type 316L as biomaterial for long term implants, we propose for the new stem component to use a TiN coating obtained using magnetron sputtering technique. The cytotoxicity studies were performed using a CCl 81 (VERO) stabilized cellular line, in order to analyse the biocompatibility properties. The samples were examined for the development of the cellular culture, in order to compare the results obtained using direct contact method. From the point of view of these tests, it was not observed an essential modification of cells and the cellular morphology is not affected by the presence of the TiN coated metallic samples. In the conclusion, the new geometry proposed for a stem component of cemented hip prosthesis could be made using different mechanical processing techniques and appears to be a potential solution in order to solve the problems related to the stability of the total hip prosthesis, with improved biocompatibility properties due to the TiN coatings.

Abstract: The research for an ideal hip prosthesis has led to the development of several durable materials that have been tested very intensly during the past decades, both clinically and mechanically. Alumina on alumina bearing has proven to be a very reliable bearing and is used more and more often. Nevertheless, because of the lack of ductility of alumina ceramic, concerns have been raised regarding its risk of fracture. The purpose of our study is to evaluate the mid-term results (78 months follow-up) of alumina on alumina prosthesis and the complications that have appeared regarding to the properties of the implant. We have reviewed retrospectively 89 THA performed in our clinic during October 2005 – October 2013 on a follow-up period of maximum 78 months. The mean age of the patients included was 49,60 years for men and 48,44 years for women. It was used a single kind of implant with same type of alumina parts, applied only on a postero-lateral surgical approach. The survival rate of ceramic-on-ceramic bearing surface by itself was 98.87% (88 out of 89). The most frequent complication was the dislocation of the prosthesis that happened in 7 cases, mainly due to a malposition of the acetabular cup, without any damage done to the ceramic bearing surfaces. In the failed case we have encountered a cracked femoral head that has been previously resterilized by steam. We could conclude that the alumina on alumina prosthesis is a very reliable prosthesis regarding its durability and strength. It requires a very precise surgical technique when implanted, since almost all the complications were due to a malposition of the acetabular component. A postero-lateral wall of the liner might decrease the rate of dislocations and ceramic wear. Also, we might debate that the steam sterilization is not suitable for alumina implants, since the fractured femoral head was resterilized.

Abstract: The modularity of femoral head and femoral stem provides many benefits to surgeons. However, case-reports have shown failure in large head Metal-on-Metal hip replacement due to trunnionosis. The exact causes of trunnionosis are not yet identified but the additional interface at the modular joint seems to be a contributing factor. In this study, a three dimensional non-linear finite element model was created to analyse the effects of head size and trunnion design on the micromotion at the head-neck interface. Four different metal head sizes and two trunnions designs and materials were used in the model. The femoral heads were assembled onto the trunnions with 7kN axial force and one cycle of gait load was applied to the head after assembly. The study showed that the micromotion was substantially increased in femoral head larger than 36mm. Trunnions material has greater effect on micromotion than trunnion design, particularly with the larger head sizes. The stability at the modular junction is important. Our findings suggest that there is a limit of assembly force to maintain enough stability on the joint; beyond this limit; the maximum micromotion will not be affected.

Abstract: Salat as a daily Muslim activitiy in praying contains several movements which are not suggested by orthopaedic doctor to be conducted by patient with total hip replacement (THR). Sujud and sitting are two movements in Salat which is recommended to be done above the chair for THR patients. There are lacks of scientific discussions about the consequences of the normal salat movement for Muslim THR patients. This paper observes the effect of these movements to the artificial hip joint in THR patient body. A three-dimensional finite element simulation is used to investigate the resisting moment, the contact pressure and the von Mises stress. An artificial hip joint model proposed by previous researcher is used in the simulations. The results show that sujud induces the impingement and plastic deformation whereas sitting is relatively safe to be conducted by THR patients. Some suggestions are also discussed with respect to the design of new artificial hip joint model which allows THR patients to conduct Salat in a normal way. The reduction of inset at the liner, the new profile at circumferential edge inner liner and the increase in the femoral head diameter can be considered as a guideline for new design of the artificial hip joint for Muslim.

Abstract: In this changing global scenario, modification, transplantation, and replacement can be the eternal solution for most of the problems in the medical field. Hence replacement technique finds a very prominent place in medicine as a remedy having closely tied up with biomechanics. One of the most important joints in the human body is the hip joint, the big and complex joint. Many researches were conducted and many are in progress, but most of these works use simplified models with either 2D or 3D approaches. The hip joint is formed by four components like femoral head cortical bone, stem, and neck. In this system we can find orthotropic and isotropic materials working together. The main objective of this research is to develop a three dimensional surface and solid finite element model of the hip joint to predict stresses in its individual components. This model is a geometric non-linear model, which helps us understand its structural mechanical behavior, seeming to suggest with advanced research in the future new hip joint prosthesis, as well as to prove the prosthesis joint interaction before being implanted in the patient. This research explains a complete human hip joint model without cartilaginous tissue, using ANSYS 10.0 Multiphysics Analysis for nine different postures in hip joint using three different materials (CoCr, Ti6Al4V, and UHMWPE) to calculate fatigue life. The result obtained from the analysis of surface model and solid model serve to help in predicting the life cycle, surface characteristics, shear stress in XY plane, stress concentration and areas that are prone to failure. Von Mises stress on the surface of our model facilitates us to equip and design an optimized prosthesis device having unique materials composition , with a highly bio-compatible and durable alloy at a low cost could be produced. In this way, a first important step towards the structural characterization of human hip joint has been developed.

Abstract: Bone loss and bone thickening phenomenon occurred due to different stiffness of the implant and femur. Implant with stiffer materials than the bone carries majority of the load and it transferred down along the implant till the distal tip of the stem. Both phenomenons contribute to stress shielding and loosening of the prosthesis stem. In this study, the stress distributions in intact femur and THR femur are established using finite element method. The THR femur model consists of cemented hip Ti6Al4V and CoCrMo prosthesis stem implanted inside the femur bone. Effects of different material properties of the prosthesis stem on the resulting stress distributions are investigated. Results shows that the largest discrepancy in stress values between intact and THR femur is predicted along the middle region at both lateral and medial planes. The distal region shows that the calculated stress for both THR femur experienced higher stress magnitude than that of intact femur. The higher stress in THR femur leads to bone thickening at the particular region. The corresponding stress magnitude saturates at 25 MPa for THR femur while intact femur is slightly lower at 22 MPa.

Abstract: A wide variety of materials are currently under consideration for use in biomedical implants. Within the scope of certain implants is the need to withstand extensive wear created by repeated use and pressure on high stress joints. Substantial research is directed toward metal-onmetal technology and cobalt chrome molybdenum (CoCrMo) is a prime candidate given its longevity [1]. Wear-resistant surface coatings for the standard CoCrMo biomedical alloy may be a simple and effective way to extend implant lifetime. In this study, we show that an initial plasma nitriding step for CoCrMo alloy is beneficial for attaining adhesion of a nanostructured diamond coating subsequently grown by microwave plasma chemical vapor deposition (CVD). The initial plasma nitriding step is quickly and easily performed in the CVD reactor and results in the formation of chromium nitride phases (CrN, Cr2N) as well as a phase transformation of cobalt from hexagonal to face centered cubic. We suggest that the success in terms of achieving adhesion of the diamond coating to the CoCrMo alloy involves chromium nitride phases acting as a diffusion barrier to carbon, thus preventing direct reaction of carbon with cobalt and the extensive graphitization that would follow.