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In replacement surgery of the hip joint, an implant is replaced into the natural femur which recreates the articulation and functionally of a natural joint. Total hip replacement is significantly increasing by the day worldwide and is likely to increase by 174% by 2030. Primary revision is another major concern for total hip replacement with revision rates likely to increase by 137%. The first part of the article states the basic anatomy of the hip joint, different ligaments in the hip, the disorders associated with the joint, and evaluation of total hip arthroplasty. In the second part some of the major works are highlighted followed by a detailed discussion about different design considerations and wear-related issues in hip joints. More emphasis is given to the tribological behavior of implants under different conditions. The design aspects and several parameters which affect the wear rate in implants are summarized. Also, different testing methods which are used both in experimental and numerical techniques are reported to estimate the wear rates in hip implants with the evolution of hip implants since the early 20th century, in terms of different designs, materials and wear hip implant arthroplasty is known as one of the best advancements in healthcare. Further research is needed to establish to improve the life expectancy of hip implants.

Advances in Finite Element Analysis has made tremendous progress in its application to study stress pattern in dentistry especially in implant prosthodontics. Titanium implant material prosthesis is used in most of the restoration or replacement of lost teeth over last three decades. Some of the prevailing titanium implant failures and limitations due to various reasons has resulted in alternative materials with more compatibility. In the present study, an attempt is made to compare stress distribution of zirconia implant material with titanium. Stress distribution and deformation in bone surrounding implant are compared by these two materials. Results obtained showed zirconia implant demonstrated similar stress patterns compared to titanium implant assembly and also agree well with the available literature. [ABSTRACT FROM AUTHOR]

The main aim of this work was evaluation of the displacements, strains and stresses in components of knee endoprosthesis by means of Finite Element Method. The semi-constrained knee endoprosthesis instrumented into femur and tibia bones was chosen for the analysis. The first step was preparation of full knee endoprosthesis geometrical model which was developed on a basis of a real model. Using reverse engineering methods containing 3D scanning and post-processing, model was obtained and then modified due to analysis assumptions. To carry out an analysis it was necessary to develop a femur and tibia bone models, which were obtained from MRI scans. Next a grid for finite-element method calculations was generated for the geometrical model. Mesh was next optimized to obtain high quality elements along with simplification of calculations. Subsequently it was necessary to specify and set the edge conditions to reflect appropriately the phenomena taking place in the real system. The system was loaded with axial force from femur proximal joint surface to tibia distal joint surface in range of 500-2000 N. Calculations were realized for endoprosthesis components made of chromium alloy for femoral joint surface part, UHMWPE for plastic sliding bearing and five different titanium alloys for endoprosthesis femoral part stem and tibial implant part - Table 1. On a basis of obtained results, the highest values of reduced stress in endoprosthesis elements were observed in the stems of both femoral and tibial part. Stress in bone didn't exceed its compression strength for all of chosen materials. The biomechanical analysis may form the basis for improving the geometry of analyzed endoprostheses and optimizing a selection of the mechanical properties of the material used to manufacture them. [ABSTRACT FROM AUTHOR]

• von Mises stresses and total deformation under different loading conditions are used to evaluate the performance of the implant. • ANSYS R-19.0 is used to evaluate Mises stresses, total deformation at head-neck junction with varying femoral head size, and taper lengths. • Circular-shaped stem hip implants are used for the analysis with a stem length of 180 mm. • The results revealed that the von Mises stresses in the complete implant tend to decrease with an increase in the femoral head size. Maximum 5% variation in stress values when 36mm femoral head is compared with 44 mm. • Optimal taper length with an increase in the femoral head size is advised to consider to reduce the revision surgery rate. • This study helps to evaluate the performance of circular-shaped hip implant using the von Mises stresses, total deformation at head-neck junction with varying femoral head size, and taper lengths using ANSYS R-19.0. Total hip arthroplasty is known as one of the best advancements in orthopedics in the 20th century. Due to age or trauma hip joint has to replace by an artificial implant. After the hip arthroplasty, the patients can return to normal day-to-day activities with a normal range of motion. There are several types and designs are currently available. These designs usually depend upon the anatomy of the patients. There is a need for revision surgery due to dislocation and aseptic loosening in these joints over time in actively younger patients. Minor changes in the design stage can certainly improve the life expectancy of the implant and will also further reduce the revision rate. In this current work, finite element analysis is carried out by varying the neck length with a change in femoral head size for a circular-shaped stem. The effects of using a shorter neck are analyzed. A total of nine combinations are considered for analysis. Modeling is carried out in CATIA V-6 and analysis is performed in ANSYS R-19. A femoral head of 36, 40, and 44 mm and taper neck length of 18, 16, and 14 mm is considered. CoPE is considered as the material combination for all the models. It was observed that the von Mises stresses in the complete implant tend to decrease with an increase in the femoral head size. Maximum 5% variation in stress values when 36 mm femoral head is compared with 44 mm. The stresses in the taper neck region tend to decrease with a decrease in the neck length. Minimum von Mises stress of 161.83 MPa was found for the complete implant and in the head-neck region, a minimum von Mises stress found 91.9 MPa. Performance evaluation of hip implant under static loading conditions gives a clear idea about the behavior of implant. It was found that a decrease in the von Mises stresses with a decrease in the taper length. However, these variations won't affect much in the performance of the hip implant. Also, a reduction in taper length can significantly increase the dislocation in the implant. So it is advised to consider the optimal taper length with an increase in the femoral head size. [ABSTRACT FROM AUTHOR]