Investigation of contact behavior on a model of the dual-mobility artificial hip joint for Asians in different inner liner thicknesses.

BACKGROUND: The four components that make up the current dual-mobility artificial hip joint design are the femoral head, the inner liner, the outer liner as a metal cover to prevent wear, and the acetabular cup. The acetabular cup and the outer liner were constructed of 316L stainless steel. At the same time, the inner liner was made of ultra-high-molecular-weight polyethylene (UHMWPE). As this new dual-mobility artificial hip joint has not been researched extensively, more tribological research is needed to predict wear. The thickness of the inner liner is a significant component to consider when calculating the contact pressure. AIM: To make use of finite element analysis to gain a better understanding of the contact behavior in various inner liner thicknesses on a new model of a dual-mobility artificial hip joint, with the ultimate objective of determining the inner liner thickness that was most suitable for this particular type of dual-mobility artificial hip joint. METHODS: In this study, the size of the femoral head was compared between two diameters (28 mm and 36 mm) and eight inner liner thicknesses ranging from 5 mm to 12 mm. Using the finite element method, the contact parameters, including the maximum contact pressure and contact area, have been evaluated in light of the Hertzian contact theory. The simulation was performed statically with dissipated energy and asymmetric behavior. The types of interaction were surface-to-surface contact and normal contact behavior. RESULTS: The maximum contact pressures in the inner liner (UHMWPE) at a head diameter of 28 mm and 36 mm are between 3.7-13.5 MPa and 2.7-10.4 MPa, respectively. The maximum von Mises of the inner liner, outer liner, and acetabular cup are 2.4-11.4 MPa, 15.7-44.3 MPa, and 3.7-12.6 MPa, respectively, for 28 mm head. Then the maximum von Mises stresses of the 36 mm head are 1.9-8.9 MPa for the inner liner, 9.9-32.8 MPa for the outer liner, and 2.6-9.9 MPa for the acetabular cup. A head with a diameter of 28 mm should have an inner liner with a thickness of 12 mm. Whereas the head diameter was 36 mm, an inner liner thickness of 8 mm was suitable. CONCLUSION: The contact pressures and von Mises stresses generated during this research can potentially be exploited in estimating the wear of dual-mobility artificial hip joints in general. Contact pressure and von Mises stress reduce with an increasing head diameter and inner liner's thickness. Present findings would become one of the references for orthopedic surgery for choosing suitable bearing geometric parameter of hip implant.

Patient-specific finite element analysis for assessing hip fracture risk in aging populations.

The femur is one of the most important bone in the human body, as it supports the body's weight and helps with movement. The aging global population presents a significant challenge, leading to an increasing demand for artificial joints, particularly in knee and hip replacements, which are among the most prevalent surgical procedures worldwide. This study focuses on hip fractures, a common consequence of osteoporotic fractures in the elderly population. To accurately predict individual bone properties and assess fracture risk, patient-specific finite element models (FEM) were developed using CT data from healthy male individuals. The study employed ANSYS 2023 R2 software to estimate fracture loads under simulated single stance loading conditions, considering strain-based failure criteria. The FEM bone models underwent meticulous reconstruction, incorporating geometrical and mechanical properties crucial for fracture risk assessment. Results revealed an underestimation of the ultimate bearing capacity of bones, indicating potential fractures even during routine activities. The study explored variations in bone density, failure loads, and density/load ratios among different specimens, emphasizing the complexity of bone strength determination. Discussion of findings highlighted discrepancies between simulation results and previous studies, suggesting the need for optimization in modelling approaches. The strain-based yield criterion proved accurate in predicting fracture initiation but required adjustments for better load predictions. The study underscores the importance of refining density-elasticity relationships, investigating boundary conditions, and optimizing models throughin vitrotesting for enhanced clinical applicability in assessing hip fracture risk. In conclusion, this research contributes valuable insights into developing patient-specific FEM bone models for clinical hip fracture risk assessment, emphasizing the need for further refinement and optimization for accurate predictions and enhanced clinical utility.

Air-Abrasion in Dentistry: A Short Review of the Materials and Performance Parameters.

The selection of abrasive material and parameters of the Air-Abrasion device for a particular application is a crucial detail. However, there are no standard recommendations or manuals for choosing these details; the operator must depend on his experience and knowledge of the procedure to select the best possible material and set of parameters. This short review attempts to identify some of the effects that the selection of material and parameters could have on the performance of the Air-Abrasion procedure for a particular application. The material and parameter data are collected from various studies and categorized according to the most popular materials in use right now. These studies are then analyzed to arrive at some inferences on the performance of Air-Abrasion materials and parameters. This review arrives at a few conclusions on the effectiveness of a material and parameter set, and that there is potential for developments in the area of standardizing parameter selection; also, there is scope for further studies on Bio-Active Glass as an alternative to the materials currently used in Air-Abrasion.

In-silico investigation of 4-nitro-N-1H-pyrazol-3-ylbenzamide towards its potential use against SARS-CoV-2: a DFT, molecular docking and molecular dynamics study.

In the present research work, we report the synthesis and characterization of novel pyrazole derivative obtained by the condensation reaction of 4-nitro benzaldehyde group with one equivalent of the 2-amino pyrazole yielding 4-nitro-N-1H-pyrazol-3-ylbenzamide with high yield. The two symmetry-independent molecules (molecule A and molecule B) differ about the central C-N bond, with the dihedral angles between the pyrazole ring system and the nitrobenzene ring being 13.90° and 18.64°, respectively. By optimizing the symmetry-independent dimer molecules, the rotational barrier between the conformers is found to be within the 2.5-5.5 kcal/mol range. QTAIM and RDG based NCI isosurface revealed the presence of strong N-H…N and C-H…O hydrogen bonds which stabilize the two independent centrosymmetric inversion-related dimers. Further, weak and short directional interactions such as C-H…N, H…H and C-H…π were also analyzed systematically using various topological parameters. The compound is found to adhere to the Lipinski's rule of five and exhibit good pharmacokinetic properties. The results of molecular docking studies performed against SARS-CoV-2 virus main protease (PDB IDs: 6LU7, 6W9C and 6WQF) revealed that the compound showed better docking scores. Molecular docking studies verified the inhibition activity of the synthesized novel compound. Finally, the binding free energy and contributed energies were calculated using MM-GBSA method. The 6LU7-ligand complex showed highest binding free energy and among all other interactions, the contributions of the covalent binding and van der Waals energy are found to be significant.Communicated by Ramaswamy H. Sarma.

Finite element analysis of elliptical shaped stem profile of hip prosthesis using dynamic loading conditions.

Patient-specific dynamic loadings are seldom considered during the evaluation of hip implants. The primary objective of this study is to check for the feasibility of the use of UHMWPE as the material for an acetabular cup o CoCr Alloy that is reported to produce a squeaking sound after replacement. An elliptical shaped stem with three different cross-sectional profiles is considered for simulation. Using a commercial finite element method, patient-specific dynamic forces were applied for the quantitative analysis. The loading and boundary conditions are used as per ISO and ASTM standards. The walking gait cycle is used with two widely used biocompatible materials: titanium and cobalt-chromium. Initially, only the stem is considered for the analysis to finalize the best out of the three profiles, along with the better material for the stem. Later the complete implant is used for the analysis. Profile 1 exhibits 1.25 and 1.17 times greater stress than Profile 2 for CoCr Alloy and Ti-6Al-4V, respectively. Similarly, Profile 3 displays stresses 1.26 and 1.25 times greater than Profile 2 for CoCr Alloy and Ti-6Al-4V, respectively. Comparatively, displacement in stem Profile 2 is 1.75 times higher in Ti-6Al-4V than CoCr Alloy. The full implant displacement at 14% gait cycle is 1.15% higher for the CoCr-acetabular column material combination when compared to UHMWPE. It can be concluded that UHMWPE can be used as the acetabular cup material instead of CoCr for the Profile 2 elliptical shaped hip implant to prevent squeaking after replacement.

Wear estimation of hip implants with varying chamfer geometry at the trunnion junction: a finite element analysis.

The hip joint helps the upper body to transfer its weight to lower body. Along with age, there are various reasons for the degeneration of the hip joint. The artificial hip implant replaces the degenerated hip. Wear between the joints is the primary cause of the hip implant becoming loose. The wear can occur due to various reasons. Due to this revision surgery are most common in young and active patients. In the design phase of the implant if this is taken care then life expectancy of the implant can be improved. Small design changes can significantly enhance the implant's life. In this work, elliptical-shaped hip implant stem is designed, and linear wear is estimated at trunnion junction. In this work, a 28 mm diameter femoral head with a 4 mm thick acetabular cup and a 2 mm thick backing cup is used. The top surface taper radiuses are changed. Solid works was used to create the models. Ansys was used to perform the analysis. It was found that as the radius of the TTR decreased, the wear rate decreased. The least wear rate was found in 12/14 mm taper with a value of 1.15E-02mm year-1for the first material combination and with a value of 1.23E-02mm year-1for the second material combination. In the comparison between the models with 1 mm chamfer and no chamfer, it was found that the wear rate was lower for the models with 1 mm chamfer. When the chamfer was increased (more than 1 mm), the linear wear increased. Wear is the main reason for the loosening of hip implants, which leads to a revision of an implant. It was found that with a decrease in TTR, there was a small increase in the linear wear rate. Overall, the implant with TTR 6 mm and a chamfer of 1 mm was found to have the least wear rate. To validate these results, the implant can be 3D printed and tested on a hip simulator.

Wear estimation of trapezoidal and circular shaped hip implants along with varying taper trunnion radiuses using finite element method.

BACKGROUND AND OBJECTIVE: The hip joint is the vital joint that is responsible for the bodyweight transfer from the upper body to the lower body. Due to age these joints are worn out and need to be replaced by artificial hip implants. Wear is the predominant factor that is responsible for the loosening of hip implants. The wear occurs between the joints due to various reasons. The wear estimation at the design stage gives a clear idea about the life of the implants and also minor changes in the design may also significantly increase the life expectancy of the implant which can further reduce the rate of revision surgery. The linear wear rate is estimated in the taper trunnion surface. METHODS: In this study, the circular and trapezoidal-shaped stem implant is designed, and wear studies are performed at the trunnion junction. The femoral head of size 28 mm, acetabular cup thickness of 4 mm, and a backing cup of thickness 2 mm are considered for the study. The neck taper radiuses at the top surface are altered. Ansys is used to perform the simulations. RESULTS: At the time of assembly of the femoral head into the stem, the stresses were found to be increasing with an increase in the top surface radius of the neck taper junctions. However, when the walking conditions are considered for wear estimation of implants the circular implants with the 12/14 mm taper exhibited the lesser linear wear rate of 0.003 mm/year. The trapezoidal implants with the 10/14 mm taper exhibited a lesser linear wear rate of 0.032 mm/year. CONCLUSIONS: Wear is an important parameter that leads to the revision of implants due to loosening. It is found that with the decrease in the taper radius at the top surface against the standard 12/14 mm taper there is no significant decrease in the wear rate at the taper junction. Overall the circular implants exhibited less wear rate results over the trapezoidal-shaped stem implants. Due to the less linear wear rate, the circular implant has a higher life over the trapezoidal-shaped implant. Further, these implants can be manufactured to test using a hip simulator with the same conditions to validate the obtained results.

Corrigendum to "Static structural analysis of different stem designs used in total hip arthroplasty using finite element method" [Heliyon Volume 5, Issue 6, June 2019, Article e01767].

[This corrects the article DOI: 10.1016/j.heliyon.2019.e01767.].

Finite Element Analysis of Different Hip Implant Designs along with Femur under Static Loading Conditions.

BACKGROUND: The hip joint is the largest joint after the knee, which gives stability to the whole human structure. The hip joint consists of a femoral head which articulates with the acetabulum. Due to age and wear between the joints, these joints need to be replaced with implants which can function just as a natural joint. Since the early 19th century, the hip joint arthroplasty has evolved, and many advances have been taken in the field which improved the whole procedure. Currently, there is a wide variety of implants available varying in the length of stem, shapes, and sizes. MATERIAL AND METHODS: In this analytical study of femur, circular, oval, ellipse and trapezoidal-shaped stem designs are considered in the present study. The human femur is modeled using Mimics. CATIA V-6 is used to model the implant models. Static structural analysis is carried out using ANSYS R-19 to evaluate the best implant design. RESULTS: All the four hip implants exhibited the von Mises stresses, lesser than its yielded strength. However, circular and trapezoidal-shaped stems have less von Mises stress compared to ellipse and oval. CONCLUSION: This study shows the behavior of different implant designs when their cross-sections are varied. Further, these implants can be considered for dynamic analysis considering different gait cycles. By optimizing the implant design, life expectancy of the implant can be improved, which will avoid the revision of the hip implant in active adult patients.

Static structural analysis of different stem designs used in total hip arthroplasty using finite element method.

BACKGROUND: The Hip joint is the primary joint which gives stability to the human body. The wear and tear associated with age and other factors, require these joints to be replaced by implants using hip arthroplasty surgeries. Cobalt chromium alloy (CoCr), titanium alloy, stainless steel are some of the most common hip joint materials used for hip implants. The design requirement for hip joint implants are very stringent to avoid revision joint surgeries due to aseptic loosening. There are various choices in shapes and materials used for stem and acetabular designs. This makes it more difficult to make an informed decision on the type of design and material that can be used for hip implants. METHODS: Circular, Oval, ellipse and trapezoidal designs with three individual cross sections (defined as profile 1, profile 2 and profile 3) are considered for the study. All models are modeled using CATIA V-6. Static structural analysis is performed using ANSYS R-19 to arrive at the best possible design and material combination for stem and acetabular cup. RESULTS: It was found that, profile 2 of all the four designs has the lowest possible deformation and von Mises stress when compared to profile 1 and profile 2. In general, profile 2 with trapezoidal stem has best outcomes in terms of its mechanical properties. Besides, stem designed with material CoCr and its associated acetabular cup with CoC (ceramic on ceramic) material can produce an implant having better properties and longer durability. CONCLUSIONS: CoCr was found to be the preferred choice of material for stem design. It was also observed that, irrespective of material considered for the analysis profile 2 with trapezoidal stem showcased lesser deformation and von Mises stress over the other eleven models. For analysis involving acetabular cups, CoC implants exhibited better mechanical properties over the conventional CoPE (Ceramic on polyethylene) materials such as Ultra-high molecular weight polyethylene (UHMWPE). It is inferred from the findings of this study that, the profile 2 with trapezoidal stem design made of CoCr material and acetabular cup made of CoC material is best suited for hip joint implants.