Contact of Rough Surfaces in Ankle Implants Under Combined Normal and Twist Loading

2018 ◽  
Vol 1 (4) ◽  
Author(s):  
Mohammad Hodaei ◽  
Kambiz Farhang
Keyword(s):  
Medical Application ◽  
Roughness Effects ◽  
Implant Surface ◽  
Surface Separation ◽  
Lateral Contact ◽  
Medical Issues ◽  
The Mean ◽  
Scale Roughness ◽  
Approximate Equations ◽  
Comprehensive Study

The medical application of implant replacements to remedy the pain in joints has necessitated a comprehensive study of wear due to contact of implant surfaces. Excessive wear can lead to toxicity and other implant associated medical issues such as patient discomfort and decreased mobility. Since implant wear is the result of contact between surfaces of tibia and talus implant, it is important to establish a model that can address implant surface contact mechanics with roughness effects. In this research, a statistical contact model is developed for the interaction of tibia and talus including normal and lateral contact in which surface roughness effects are included. The model accounts for the elastic–plastic interaction of the implant surface with roughness. For this purpose, tibia and talus implants are considered as macroscopic surfaces containing micron-scale roughness. Approximate equations are obtained that relate the contact force to the mean surface separation explicitly. Closed-form equations are obtained for hysteretic energy loss in implant using the approximate equations. Such a function can serve as a very useful tool for implant designers and manufacturers. Natural frequencies of both adduction-abduction and planter-dorsiflexion rotations are obtained using nonlinear vibration analyses.

EFFECT OF ROUGH SURFACE ASYMMETRY ON CONTACT ENERGY LOSS IN HIP IMPLANTS

2017 ◽  
Vol 17 (01) ◽  
pp. 1750023 ◽  
Author(s):  
MOHAMMAD HODAEI ◽  
KAMBIZ FARHANG
Keyword(s):  
Energy Loss ◽  
Weibull Distribution ◽  
Rough Surface ◽  
Contact Force ◽  
Integral Function ◽  
Height Distribution ◽  
Implant Surface ◽  
Surface Separation ◽  
Contact Frequency ◽  
Approximate Equations

Rough surface height distribution can be nonsymmetric, depending on the process of surface preparation. The prevalent processes for implant surface involve turning and milling, both resulting in surface height distributions of nonsymmetric nature. Asymmetry in a surface height distribution is manifested through a parameter known as skewness. Unlike Gaussian distribution, Weibull distribution permits characteristics such as skewness and kurtosis in data to be included in the mathematical description of a height distribution. This paper develops hip implant contact model based on Weibull distribution of surface heights. The elastic–plastic interaction of implant surfaces are considered as macroscopically spherical surfaces containing micron-scale roughness. Symmetric and asymmetric roughness height distribution are compared. The total contact force is related to the minimum mean surface separation of the contacting rough surfaces. The force is obtained using statistical integral function of the asperity heights over the possible region of interaction of the roughness of surfaces. Approximate equations are obtained that relate the contact force to the minimum mean surface separation explicitly. The approximate equations are used to derive hysteretic energy loss per load–unload sequence, contact frequency, and damping. It is shown that energy loss per cycle, contact frequency, and damping are lower for asymmetric surface roughness distribution.

scholarly journals Gender-wise Comparative Assessment of Lifestyle Patterns and Well-being Status among Healthcare Employees at a Tertiary Care Hospital

2021 ◽  
Author(s):  
Vanajakshamma Velam ◽  
Vyshnavi Kancherla ◽  
Latheef Kasala ◽  
Anusha Kancherla ◽  
Mounica Reddy Pillaram
Keyword(s):  
Tertiary Care Hospital ◽  
Tertiary Care ◽  
Well Being ◽  
Care Hospital ◽  
Cross Sectional ◽  
Significant Difference ◽  
Female Employees ◽  
The Mean ◽  
Lifestyle Patterns ◽  
Comprehensive Study

Abstract Background This study was an attempt to assess and compare the gender-wise lifestyle patterns and well-being status among the employees of a tertiary care teaching hospital. Material and Methods This is a cross-sectional, questionnaire-based study conducted at a tertiary care hospital between May and August 2019. A total of 777 employees belonging to both genders (male and female) and working at different professional levels were assessed. All the enrolled employees were subjected to a comprehensive study tool consisting of various dimensions of their health, which included physical, mental, social, spiritual and intellectual health dimensions. Results Among the participants, 327 (42.1%) were male and 450 (57.9%) were female. There was no significant difference in the mean age of male (37.91 ± 7.52) and female (36.85 ± 8.16) employees (p = 0.07). A significantly higher proportion of diabetes and hypertension were seen in male employees (9.8% and 14.4%, respectively) than in female (5.6% and 6.2% respectively). The overall well-being was better in male employees than in females and was statistically significant (p < 0.0001). We found that male employees had statistically significant better well-being in terms of physical, mental and social health whereas female employees had intellectual health. Conclusion The overall well-being in healthcare staff was good at our tertiary care hospital, and the outstanding/good well-being rate was higher in male employees than in female employees. Female employees experienced risks with regard to their physical health.

scholarly journals Assessment of the Tissue Response to Modification of the Surface of Dental Implants with Carboxyethylphosphonic Acid and Basic Fibroblastic Growth Factor Immobilization (Fgf-2): An Experimental Study on Minipigs

Biology ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 358
Author(s):  
Javier Aragoneses ◽  
Ana Suárez ◽  
Nansi López-Valverde ◽  
Francisco Martínez-Martínez ◽  
Juan Manuel Aragoneses
Keyword(s):  
Surface Treatment ◽  
Test Group ◽  
Mean Value ◽  
Control Group ◽  
P Value ◽  
Implant Surface ◽  
Bone Contact ◽  
Bone Implant ◽  
Significant Difference ◽  
The Mean

The aim of this study was to evaluate the effect of implant surface treatment with carboxyethylphosphonic acid and fibroblast growth factor 2 on the bone–implant interface during the osseointegration period in vivo using an animal model. The present research was carried out in six minipigs, in whose left tibia implants were inserted as follows: eight implants with a standard surface treatment, for the control group, and eight implants with a surface treatment of carboxyethylphosphonic acid and immobilization of FGF-2, for the test group. At 4 weeks after the insertion of the implants, the animals were sacrificed for the histomorphometric analysis of the samples. The means of the results for the implant–bone contact variable (BIC) were 46.39 ± 17.49% for the test group and 34.00 ± 9.92% for the control group; the difference was not statistically significant. For the corrected implant–bone contact variable (BICc), the mean value of the test group was 60.48 ± 18.11%, and that for the control group, 43.08 ± 10.77%; the difference was statistically significant (p-value = 0.035). The new bone formation (BV/TV) showed average results of 27.28 ± 3.88% for the test group and 26.63 ± 7.90% for the control group, meaning that the differences were not statistically significant (p-value = 0.839). Regarding the bone density at the interthread level (BAI/TA), the mean value of the test group was 32.27 ± 6.70%, and that of the control group was 32.91 ± 7.76%, with a p-value of 0.863, while for the peri-implant density (BAP/TA), the mean value of the test group was 44.96 ± 7.55%, and that for the control group was 44.80 ± 8.68%, without a significant difference between the groups. The current research only found a significant difference for the bone–implant contact at the cortical level; therefore, it could be considered that FGF-2 acts on the mineralization of bone tissue. The application of carboxyethylphosphonic acid on the surface of implants can be considered a promising alternative as a biomimetic coating for the immobilization of FGF-2. Despite no differences in the new bone formation around the implants or in the interthread or peri-implant bone density being detected, the biofunctionalization of the implant surface with FGF-2 accelerates the mineralization of the bone–implant interface at the cortical level, thereby reducing the osseointegration period.

Section plane selection influences the results of histomorphometric studies: the example of dental implants

2012 ◽  
Vol 57 (5) ◽  
Author(s):  
Sigmar Kopp ◽  
Mareike Warkentin ◽  
Ferenc Öri ◽  
Peter Ottl ◽  
Günther Kundt ◽  
...  
Keyword(s):  
Section Plane ◽  
Section Thickness ◽  
Implant Surface ◽  
Bone Implant ◽  
Osseointegrated Implants ◽  
Section Technique ◽  
Significant Difference ◽  
Bone To Implant Contact ◽  
The Mean ◽  
Dependent Samples

AbstractThis study was designed to determine and statistically analyze bone-to-implant contact (BIC) values for human specimens segmented in at least two different locations.Samples of human bone with fractured osseointegrated implants were obtained from six patients. Sections were prepared, dehydrated, and resin infiltrated. Undecalcified bone sections were produced using the thin-section technique according to Donath, ultimately obtaining a section thickness of approximately 20 μm. Fifteen specimens were available for histomorphometry. The bone sections were digitized and analyzed. The bone-to-metal contact (BMC) parameter was determined histomorphometrically. The BMC was returned in terms of the visibly bone-covered implant surfaces as a percentage of the total implant surface shown.The values obtained for the six implants were arranged as six maximum-distance pairs and tested for significance using the t-test for dependent samples. The mean difference in BIC was 11.69±9.79%. The two-sided test showed a significant difference (p=0.033).The accidental or deliberate choice of section plane for a bone-implant block has an influence on the BIC value. To make BIC values more comparable, a standardization of section planes is desirable.

DDC Lubrication: A New Concept in Tribology

1992 ◽  
Vol 114 (1) ◽  
pp. 181-185 ◽  
Author(s):  
K. To̸nder
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Gap Function ◽  
Upper And Lower Bounds ◽  
Roughness Effects ◽  
Cavity Depth ◽  
Roughness Amplitude ◽  
Previously Treated ◽  
The Mean ◽  
Expansion Scheme

A new lubrication concept is presented, Deep Disconnected Cavities. It differs from the lubrication of microcavities, previously treated by other authors, by the deepness of the cavities. The validity of Reynolds’ equation and nonturbulent conditions are assumed. By a Taylor expansion scheme, it is shown that the roughness effects are expressible in terms of roughness factors modifying the Reynolds equation, similar to those proposed by Patir and Cheng (1978). Unlike those established for ordinary roughness, the DDC factors are independent of local film thickness and roughness amplitude (cavity depth), and may therefore be used to modify standard hydro-dynamic parameters. By a different mathematical approach, involving upper and lower bounds on the various hydrodynamic quantities, it is found that Reynolds’ equation and all the other hydrodynamic expressions may be written just as for smooth surfaces, with the following modifications: 1. The film thickness should be expressed by the minimum gap function, and not by the mean gap function. 2. There are, in general, three effective viscosities, lower than the physical one, two of which are associated with the x and y directions respectively and appear in the modified Reynolds equation as well as in the flow terms. The third one appears only in the expression for shear stress.

Kinematic Analysis and Synthesis of Three-Input, Eight-Bar Mechanisms Driven by Relatively Small Cranks

1992 ◽  
Author(s):  
Kambiz Farhang ◽  
Partha Sarathi Basu
Keyword(s):  
Nonlinear Equations ◽  
Kinematic Analysis ◽  
Linear Equations ◽  
Output Link ◽  
Analysis And Design ◽  
Constraint Equations ◽  
Analysis And Synthesis ◽  
The Mean ◽  
Approximate Equations

Abstract Approximate kinematic equations are developed for the analysis and design of three-input, eight-bar mechanisms driven by relatively small cranks. Application of a method in which an output link is presumed to be comprised of a mean and a perturbational motions, along with the vector loop approach facilitates the derivation of the approximate kinematic equations. The resulting constraint equations are, (i) in the form of a set of four nonlinear equations relating the mean link orientations, and (ii) a set of four linear equations in the unknown perturbations (output link motions). The latter set of equations is solved, symbolically, to obtain the output link motions. The approximate equations are shown to be effective in the synthesis of three-input, small-crank mechanisms.

Closure Equations for CEB Elastic-Plastic Contact

2007 ◽  
Author(s):  
A. Sepehri ◽  
K. Farhang
Keyword(s):  
Closed Form ◽  
Integral Equations ◽  
Contact Force ◽  
Elastic Plastic ◽  
Approximate Function ◽  
The Mean ◽  
Contact Relation ◽  
Explicit Relation ◽  
Force Accuracy ◽  
Approximate Equations

The CEB elastic-plastic contact of nominally flat rough surfaces based on conservation of volume during plastic flow was forwarded by Chang, Etsion and Bogy [1]. The CEB model presents contact force as integral functions of the mean plane separation. A closed-form approximate function providing an explicit relation between contact force and surface parameters and mean plane separation would be desirable for several reasons. First, it facilitates implementation of the contact relation in the dynamics of mechanical system and, second, it provides expediency and efficiency for calculation of contact force when repetitive computation of the contact force is required. This paper presents closed-form approximate equations expressing contact force explicitly as a function of critical interference and mean plane separation. Two alternative approximate equations are provided. The first equation, in simpler form, is shown to yield error within six percent (6%) of the exact integral equations. The second form of approximate equations provides contact force accuracy within 0.1 percent of the original integral equations.

The effect of femoral head diameter upon lubrication and wear of metal-on-metal total hip replacements

2001 ◽  
Vol 215 (2) ◽  
pp. 161-170 ◽  
Author(s):  
S L Smith ◽  
D Dowson ◽  
A A J Goldsmith
Keyword(s):  
Wear Rate ◽  
Boundary Lubrication ◽  
Wear Testing ◽  
Wear Rates ◽  
Surface Separation ◽  
Lubricating Film ◽  
Lubrication Regime ◽  
Metal On Metal ◽  
The Mean ◽  
Mixed Lubrication Regime

It has been found that a remarkable reduction in the wear of metal-on-metal hip joints can be achieved by simply increasing the diameter of the joint. A tribological evaluation of metal-on-metal joints of 16, 22,225, 28 and 36 mm diameter was conducted in 25 per cent bovine serum using a hip joint simulator. The joints were subject to dynamic motion and loading cycles simulating walking for both lubrication and wear studies. For each size of joint in the lubrication study, an electrical resistivity technique was used to detect the extent of surface separation through a complete walking cycle. Wear of each size of joint was measured gravimetrically in wear tests of at least 2 × 106 cycles duration. Joints of 16 and 22.225mm diameter showed no surface separation in the lubrication study. This suggested that wear would be proportional to the sliding distance and hence joint size in this boundary lubrication regime. A 28 mm diameter joint showed only limited evidence of surface separation suggesting that these joints were operating in a mixed lubrication regime. A 36 mm diameter joint showed surface separation for considerable parts of each walking cycle and hence evidence of the formation of a protective lubricating film. Wear testing of 16 and 22.225mm diameter metal-on-metal joints gave mean wear rates of 4.85 and 6.30mm3/106 cycles respectively. The ratio of these wear rates, 0.77, is approximately the same as the joint diameters ratio, 16/22.225 or 0.72, as expected from simple wear theory for dry or boundary lubrication conditions. No bedding-in was observed with these smaller diameter joints. For the 28 mm diameter joint, from 0 to 2 × 106 cycles, the mean wear rate was 1.62 mm3/106 cycles as the joints bedded-in. Following bedding-in, from 2.0 × 106 to 4.7 × 106 cycles, the wear rate was 0.54mm3/106 cycles. As reported previously by Goldsmith in 2000 [1], the mean steady state wear rate of the 36 mm diameter joints was lower than those of all the other diameters at 0.07 mm3/106 cycles. For a range of joints of various diameters, subjected to identical test conditions, mean wear rates differed by almost two orders of magnitude. This study has demonstrated that the application of sound tribological principles to prosthetic design can reduce the wear of metal-on-metal joints, using currently available materials, to a negligible level.

scholarly journals Detonation nanodiamonds biofunctionalization and immobilization to titanium alloy surfaces as first steps towards medical application

2014 ◽  
Vol 10 ◽  
pp. 2765-2773 ◽  
Author(s):  
Juliana P L Gonçalves ◽  
Afnan Q Shaikh ◽  
Manuela Reitzig ◽  
Daria A Kovalenko ◽  
Jan Michael ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Functional Groups ◽  
Titanium Substrate ◽  
Medical Application ◽  
Carbon Surface ◽  
Detonation Synthesis ◽  
Implant Surface ◽  
Body Tissues ◽  
Biological Modification ◽  
Surface Modified

Due to their outstanding properties nanodiamonds are a promising nanoscale material in various applications such as microelectronics, polishing, optical monitoring, medicine and biotechnology. Beyond the typical diamond characteristics like extreme hardness or high thermal conductivity, they have additional benefits as intrinsic fluorescence due to lattice defects without photobleaching, obtained during the high pressure high temperature process. Further the carbon surface and its various functional groups in consequence of the synthesis, facilitate additional chemical and biological modification. In this work we present our recent results on chemical modification of the nanodiamond surface with phosphate groups and their electrochemically assisted immobilization on titanium-based materials to increase adhesion at biomaterial surfaces. The starting material is detonation nanodiamond, which exhibits a heterogeneous surface due to the functional groups resulting from the nitrogen-rich explosives and the subsequent purification steps after detonation synthesis. Nanodiamond surfaces are chemically homogenized before proceeding with further functionalization. Suspensions of resulting surface-modified nanodiamonds are applied to the titanium alloy surfaces and the nanodiamonds subsequently fixed by electrochemical immobilization. Titanium and its alloys have been widely used in bone and dental implants for being a metal that is biocompatible with body tissues and able to bind with adjacent bone during healing. In order to improve titanium material properties towards biomedical applications the authors aim to increase adhesion to bone material by incorporating nanodiamonds into the implant surface, namely the anodically grown titanium dioxide layer. Differently functionalized nanodiamonds are characterized by infrared spectroscopy and the modified titanium alloys surfaces by scanning and transmission electron microscopy. The process described shows an adsorption and immobilization of modified nanodiamonds on titanium; where aminosilanized nanodiamonds coupled with O-phosphorylethanolamine show a homogeneous interaction with the titanium substrate.

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