Search

Failure of cement mantle of bond loosening between liner and cement mantle is an important issue in total hip replacement. Two factors that commonly cause cement mantle failure are initial crack and stress. A solution for reducing stress on the cement mantle has been proposed by adding insertion material between liner and cement mantle. Nevertheless, further study is needed to optimize the proposed solution. A possible option is to vary the thickness of the insertion material. If the thickness of the PMMA material is constant, then the variation of the insertion thickness will be followed by the variation of the thickness of the liner. Consequently, the stress value on the liner will follow the variation of liner thickness. The objective of this study is to examine the effect of the thickness variation of the insertion material to stress on cement mantle and liner using finite element simulation. Results revealed that the magnitude of stress and deflection decreased in the cement mantle and the liner along with the increasing thickness of the insertion material.

The use of material for implant bearing has a vital role in minimizing failures that endanger implant recipients. Evaluation of contact pressure of bearing material can be the basis for material selection and have correlations with wear that contribute to the need of revision operations. The current paper aims to investigate three different metallic materials, namely cobalt chromium molybdenum (CoCrMo), stainless steel 316L (SS 316L), and titanium alloy (Ti6Al4V) for application in metal-on-metal bearing of total hip implant in terms of contact pressure. In silico model based on finite element simulation has been considered to predict contact pressure of metal-on-metal bearings under normal walking conditions. It is found that the use of Ti6Al-4V-on-Ti6Al4V is superior in its ability to reduce contact pressure by more than 35% compared to the other studied metal-on-metal couple bearings. [ABSTRACT FROM AUTHOR]

Due to various concerns about the use of metal-on-metal that is detrimental to users, the use of metal as acetabular cup material was later changed to ultra high molecular weight polyethylene (UHMWPE). However, the wear on UHMWPE releases polyethylene wear particles, which can trigger a negative body response and contribute to osteolysis. For reducing the wear of polyethylene, one of the efforts is to investigate the selection of metal materials. Cobalt chromium molybdenum (CoCrMo), stainless steel 316L (SS 316L), and titanium alloy (Ti6Al4V) are the frequently employed materials. The computational evaluation of contact pressure was carried out using a two-dimensional axisymmetric model for UHMWPE acetabular cup paired with metal femoral head under gait cycle in this study. The results show Ti6Al4V-on-UHMWPE is able to reduce cumulative contact pressure compared to SS 316L-on-UHMWPE and CoCrMo-on-UHMWPE. Compared to Ti6Al4V-on-UHMWPE at peak loading, the difference in cumulative contact pressure to respective maximum contact pressure is 9.740% for SS 316L-on-UHMWPE and 11.038% for CoCrMo-on-UHMWPE. [ABSTRACT FROM AUTHOR]

The wear on the acetabular liner surface of total hip prosthesis due to human activity cannot be avoided. Salat is an obligation religious activity for Muslims performed five times daily, without exception for patients who used the total hip prosthesis. Salat consists of standing, bowing, prostrating and sitting on the leg motions. Many researchers have investigated the wear on the liner surface for daily activity but not for salat activity. This study has aimed to calculate wear on the acetabular liner surface due to salat activity. A new linear wear model has been proposed in order to estimate the linear wear or the wear depth on the acetabular liner surface. In addition, a volumetric wear model or volume loss on the acetabular liner surface has also been developed based on the new linear wear model. These wear model are used to calculate wear on the acetabular liner surface due to walking and salat activities. Results show that the linear wear due to salat activity is lower than walking activity, because of the intensity of salat activity is lower than walking. However, the combinations of both wear due to walking activity and salat activity need to be considered. [ABSTRACT FROM AUTHOR]

The frictional performances of surgical sutures have been found to play a vital role in their functionality. The purpose of this paper is to understand the frictional performance of multifilament surgical sutures interacting with skin substitute, by means of a penetration friction apparatus (PFA). The influence of the size of the surgical suture was investigated. The relationship between the friction force and normal force was considered, in order to evaluate the friction performance of a surgical suture penetrating a skin substitute. The friction force was measured by PFA. The normal force applied to the surgical suture was estimated based on a Hertzian contact model, a finite element model (FEM), and a uniaxial deformation model (UDM). The results indicated that the penetration friction force increased as the size of the multifilament surgical suture increased. In addition, when the normal force was predicted by UDM, it was found that the ratio between the friction force and normal force decreased as the normal force increased. A comparison of the results suggested that the UDM was appropriate in predicting the frictional behavior of surgical suturing. [ABSTRACT FROM AUTHOR]

Loosening of the acetabular liner component caused by the failure of the cement mantle is a complex phenomenon in a total hip arthroplasty. This failure is often associated with the occurrence of cracking in the cement mantle. Investigation of this cracking can be performed by fat igue test or simulat ion. Cracking can be caused by initial cracks (porosity), defects of cement mantle, or stress due to repeated loading. An initial crack may be caused by material defects. The stress depends on the load and on the strength of the material itself. To reduce crack failure, one can minimize the init ial crack or optimize the thickness of the cement mantle and reduce stress that occurs in the cement mantle. This study offers a solution for reducing the intensity of stress on the cement mantle by providing an additional metal layer between the liner and the acetabular component cement mantle. The study is performed by simulating static contact using finite element analysis. Results show that the additional layer between the acetabular liner and the cement mantle can significantly reduce the stress on the contact surface of the cement mantle. [ABSTRACT FROM AUTHOR]

Introduction: Ultrahigh-molecular-weight polyethylene (UHMWPE) is a thermoplastic polymer useful in biomaterial applications, especially in orthopedic field. Yet, little is known concerning its initial effect on human bone marrow stem cells (hBMSCs) after implantation. Materials and Methods: A cytotoxicity analysis was performed with a 3-(4,5-dimethylthiazol 2-yl)-2,5-diphenyltetrazolium assay after 24, 48, and 72 h of incubation of hBMSC culture. Expression of interleukin-6 (IL-6) was measured using enzyme-linked immunosorbent assay. Cell viability was measured with Inhibitory concentration 50% (IC50) formula. Results: All treatment groups showed a cell viability of >50% ranging from 78% to >100%. Lower expression of IL-6 of hBMSC compared to control group was found in 48 h of incubation period. Conclusion: hBMSC showed high cell viability after initial contact with UHMWPE material. Modulation of IL-6 expression was present at the initial stage as a response to foreign material. [ABSTRACT FROM AUTHOR]

Machine components operating in sandy environments will wear because of the abrasive interaction with sand particles. In this work, a method is derived to predict the amount of wear caused by such abrasive action, in order to improve the maintenance concept of the components. A finite element model is used to simulate various tips scratching a smooth surface. The model is verified by comparing the obtained results with a set of experiments performed earlier (M. Woldman, et al., 2013, Wear, 301(1–2), pp 76–81). [ABSTRACT FROM AUTHOR]

Purpose: Human bone marrow-derived mesenchymal cell (hBMC) reactions to 316L stainless steel (316L-SS) have never been evaluated. The objective of this study was to assess cell viability and interleukin-6 expression of hBMC cultures upon treatment with a 316L-SS implant. Methods: A cytotoxicity analysis was conducted with a 3-(4,5-dimethylthiazol 2-yl)-2,5-diphenyltetrazolium (MTT) assay after a period of 24, 48 and 72 hours of incubation. Expression of interleukin-6 was measured using enzyme-linked immunosorbent assay (ELISA). Results: Cell viability measurement was performed via IC50 formula. All treatment group showed a > 50 % cell viability with a range of 56,5 - 96,9 % at 24 hours, 51,8-77,3% at 48 hours and 70,1-120 % at 72 hours. Interleukin-6 expression was downregulated subsequent to treatment with 316L-SS compared to the control group. Conclusion: We found that 316L-SS did not exhibit toxicity towards hBMC culture. [ABSTRACT FROM AUTHOR]

Tribological interactions between surgical suture and human tissue play an important role in the stitching process. The purpose of the paper is to understanding the tribological behavior of surgical suture interacting with artificial skin, with respect to surgical suture material and structure, by means of a capstan experiment approach and a contact area model. The results indicated that structure and surface topography of the surgical suture had a pronounced effect on the tribological interactions. The apparent coefficient of friction of vicryl surgical suture was the smallest among the three surgical suture materials. As the sliding velocity increased, or the applied load decreased, the coefficient of friction increased. Furthermore, stick-slip phenomena were observed during the sliding procedure. [ABSTRACT FROM AUTHOR]

A long chain alkyl phenylboric ammonium derivative (DBBM) was synthesized as a lubricating additive. The tribological performances of DBBM and combinations of DBBM and ZDDP as additives were evaluated, which suggests that DBBM has better tribological properties than ZDDP. X-ray absorption near edge structure spectroscopy was used for the analysis of thermal films and tribofilms. The results indicate that the boron in additive mainly forms trigonal and tetrahedral coordination boron both in thermal films and tribofilms, while sulfur mainly generates iron sulfate in thermal films and iron sulfide, iron disulfide, and iron sulfate in tribofilms. It also can be found that it is more likely to form low valence sulfur when the concentration of ZDDP increases in the combinations. [ABSTRACT FROM AUTHOR]

Two borate esters, one with benzotriazole (BTB) and another with 2-mercaptobenzothiazole (BMB) were synthesized and used as additives in mineral oil. BMB showed better hydrolysis stability, probably because S atoms in BMB provided negative charges to the N to enhance B←N coordination. Moreover, BMB was superior in terms of improving P B value, anti-wear and friction-reducing properties of mineral oil. XPS spectra revealed that h-BN, B 2 O 3 and Fe x O y were detected in BTB-tribofilm, while additional FeSO 4 , FeS and B 2 S 3 were found in BMB-tribofilm. The possible triple effects of S atoms in BMB can be summarized as: enhancing the B←N coordination; improving the adsorption ability of BMB on the metal surface; and generating tribochemical reaction products with tribological effects. • Borate esters with benzotriazole (BTB) and 2-mercaptobenzothiazole (BMB) were synthesized and used as additives. • S atoms in BMB molecule provide negative charges to the N atom to indirectly enhance the B←N coordination bond. • Frontier orbital energy analysis shows that BMB tends to donate, while BTB accepts electrons from iron. • BMB has good tribological properties for the contribution of S to molecular stability, adsorption and reactivity. [ABSTRACT FROM AUTHOR]

In the sliding contact between the fingerpad and a rough surface when touching a product’s surface, friction plays a role in the perception of roughness, slipperiness and warmth. For product engineers who aim to control and optimize the sensorial properties of a product surface interacting with the skin, it is essential to understand this frictional behaviour. However, the friction of skin is yet poorly understood. The variation that is observed within or between skin friction studies can be assigned to gender, age and orientation of the finger. Analysing data collected from literature shows some consistent trends. The coefficient of friction increases considerably with increasing hydration level of the skin, due to softening of the top layer of the skin. The coefficient of friction of the fingerpad decreases with normal load to a constant value, which can be attributed to effects of normal adhesion and the deformation behaviour of the fingerpad. There is no consistent effect of velocity on the coefficient of friction. Friction decreases with increasing Ra roughness. When the Ra roughness increases further, the contribution of deformation causes an increase in the friction after which it remains constant. Some influence of the finishing method is reported. The type of material has a smaller influence than the surface roughness of the sample or the condition of the skin. Even though the coefficient of friction of the fingerpad shows some consistent trends, examining the friction behaviour at a more detailed level might explain the contribution of friction to tactile perception. The measuring signal contains relevant information and should be analysed thoroughly as opposed to taking the average coefficient of friction of the steady state part of the signal. Future work should involve the study of local friction behaviour at the scale of the surface roughness. [ABSTRACT FROM PUBLISHER]

Abstract: The range of motion of artificial hip joint during human activities, measured from the postoperative total hip arthroplasty patients, has been reported previously. There were two human activities discussed, i.e. Western-style and Japanese-style. This paper analyzes the hip joint movement during human activities, based on the measured range of motion, using finite element simulation. The Western-style activities consist of picking up, getting up and sitting, while the Japanese-style activities consist of sitting on legs with fully flexed at the knee (seiza), squatting and sitting on legs with fully flexed at the knee (zarei). The aim of this study is to investigate the probability of prosthetic impingement to occur and to calculate the von Mises stress during the activities. A three-dimensional nonlinear finite element (FE) method was used in the simulation. The acetabular liner cup positions were varied. Results show that in the Western-style activities, the picking up activity induces prosthetic impingement in a certain acetabular liner cup position, whereas in the Japanese-style activities there is no prosthetic impingement observed. However, the Japanese's Zarei activity has a critical value in the range of motion. The von Mises stresses during the prosthetic impingement have been shown and the value is higher than the yield stress of the material. [Copyright &y& Elsevier]

In modelling and understanding the contact and friction behaviour of human skin, the elastic modulus of the skin is an important input parameter. For the development of design rules for the engineering of surfaces in contact with the skin an expression that describes the relation between the elastic modulus of the skin and the size of the contact is essential.Although an exact description of the mechanical behaviour of the skin requires an anisotropic, nonlinear, viscoelastic model, in this study it was found that for contact modelling involving relatively small deformations, the mechanical behaviour seems to be accurately described by a single parameter: the effective elastic modulus. The effective elastic modulus is shown to decrease several orders of magnitude when the length scale increases, which is the consequence of the rather complex anatomy of the skin. At an indentation depth of 10 µm, the effective elastic modulus was shown to decrease from 0.15 to 0.015 MPa when the radius of curvature of the indenter increases from 10 µm to 10 mm. The variation of the elasticity is explained by the variation in the composition and properties of the different skin layers. This study shows that for the contact modelling of human skin, a closed-form expression based on the anatomy of the skin exists, which yields the magnitude of the effective elastic modulus of the skin as a function of the length scale of the contact depending on variables such as age, gender and environmental conditions. [ABSTRACT FROM AUTHOR]

The selection of biomaterials for bearing in total hip arthroplasty is very important to avoid various risks of primary postoperative failure for patients. The current investigation attempts to analyze the Tresca stress of metal-on-metal bearings with three different materials, namely, cobalt chromium molybdenum (CoCrMo), stainless steel 316L (SS 316L), and titanium alloy (Ti6Al4V). We used computational simulations using a 2D axisymmetric finite element model to predict Tresca stresses under physiological conditions of the human hip joint during normal walking. The simulation results show that Ti6Al4V-on-Ti6Al4V has the best performance to reduce Tresca stress by 45.76% and 39.15%, respectively, compared to CoCrMo-on-CoCrMo and SS 316L-on-SS 316L. [ABSTRACT FROM AUTHOR]

Wear and wear-induced debris is a significant factor in causing failure in implants. Reducing contact pressure by using a textured surface between the femoral head and acetabular cup is crucial to improving the implant's life. This study presented the effect of surface texturing as dimples on the wear evolution of total hip arthroplasty. It was implemented by developing finite element analysis from the prediction model without dimples and with bottom profile dimples of flat, drill, and ball types. Simulations were carried out by performing 3D physiological loading of the hip joint under normal walking conditions. A geometry update was initiated based on the patient's daily routine activities. Our results showed that the addition of dimples reduced contact pressure and wear. The bottom profile dimples of the ball type had the best ability to reduce wear relative to the other types, reducing cumulative linear wear by 24.3% and cumulative volumetric wear by 31% compared to no dimples. The findings demonstrated that surface texturing with appropriate dimple bottom geometry on a bearing surface is able to extend the lifetime of hip implants. [ABSTRACT FROM AUTHOR]

Surgical sutures have different sizes, structures, whereas they are being used for various surgeries. The high friction performance of surgical sutures in the suturing process may cause inflammation and pain, leading to a longer recovery time. This paper presents an understanding of the tribological behavior of surgical suture with monofilament and multifilament structures, by means of a penetration friction apparatus (PFA). The results indicated that structure and surface topography of the surgical suture had a pronounced effect on the tribological interactions. It was found that the friction force and abrasion area of skin substitute with the penetration of polyglycolic acid (PGA) multifilament surgical suture were larger than that of Nylon monofilament surgical suture. Meanwhile, more abrasion at the pull-in boundary of skin substitute was observed compared with that at the pull-out boundary. [ABSTRACT FROM AUTHOR]

Failure of the cement mantle in total hip arthroplasty is not a simple phenomenon. Cracking, which can be caused by crack initiation and repeated loading, can cause loosening of the acetabular liner component. A previous study showed that addition of a metal layer between the liner and acetabular could reduce the stress at the contact surface of the cement mantle. This study elaborates on the performance of the additional layer. Several material properties of the layer were simulated using finite element analysis for maximum performance. A static contact analysis was used to simulate the stresses at the contact surface of the cement mantle. The results show that an additional layer of cobalt chrome produced the best performance.