Performance analysis of an orthopaedic biomaterial 100-station wear test system

2009 ◽  
Vol 224 (3) ◽  
pp. 697-701 ◽  
Author(s):  
V Saikko
Keyword(s):  
Wear Rate ◽  
Polyethylene Wear ◽  
Calf Serum ◽  
High Capacity ◽  
Wear Test ◽  
High Standard ◽  
Test System ◽  
Wear Rates ◽  
Two Samples ◽  
The Mean

Until recently, wear studies of orthopaedic biomaterials have suffered from inadequate testing capacity and high standard deviation (SD) of results. In the present article, the previously validated 100-station hip wear simulator, the SuperCTPOD, is evaluated with regard to its capability of producing statistically significant differences in mean wear rates. SuperCTPOD wear tests were done for 38 different types of polyethylene pins against polished CoCr discs with diluted calf serum lubrication. A total of 200 pins were worn in two consecutive tests of 6 weeks, duration each. The sample size varied from four to six. The mean wear rates of the samples ranged from 0.52 to 77.1 mg per one million cycles. On the average, the SD of the wear rate was 4.2 per cent of the mean value (range 1–8.5 per cent). A difference in the mean wear rates below 5 per cent was large enough to be statistically significant ( p <0.05) in 21 comparisons between two samples, the lowest statistically significant mean difference being 3.2 per cent. In conclusion, the high capacity and the low SD of the wear rate make the SuperCTPOD wear test system unparalleled in efficiency. The observations regarding the effect of crosslinking and molecular weight on polyethylene wear resistance were in agreement with studies published earlier.

scholarly journals A Hip Wear Simulator with 100 Test Stations

2005 ◽  
Vol 219 (5) ◽  
pp. 309-318 ◽  
Author(s):  
V Saikko
Keyword(s):  
Polyethylene Wear ◽  
Calf Serum ◽  
High Capacity ◽  
Test System ◽  
Clinical Findings ◽  
Wear Factor ◽  
Compact Size ◽  
Pin On Disc ◽  
The Mean ◽  
Wear Simulator

A novel high-capacity hip wear simulator of the pin-on-disc type was designed, built, and validated. This so-called Super-CTPOD (circularly translating pin-on-disc) device has as many as 100 separate test stations, being an advanced version of the previously validated 12-station CTPOD. A validity test was done so that in all stations the specimens and the test conditions were as similar as possible. Hence, for the first time in this field, an adequate number of similar tests was done for a proper statistical analysis of wear data. The pins were conventional, gamma-sterilized ultra-high molecular weight polyethylene, and the discs were polished CoCr. The lubricant was diluted calf serum and the test length 3 million cycles. In the course of the test, the pins became highly polished, whereas the discs remained practically unchanged. The majority of the polyethylene wear particles were rounded, with a mean diameter of 0.25 μm. The 100 wear factor values computed from the 100 steady state wear rate values of the pins were normally distributed, the mean ±95 per cent confidence interval being 1.63 ± 0.017 × 10−6 mm3/Nm. The standard deviation was 5.4 per cent of the mean. There were no outliers. The wear mechanisms and the wear factor agreed well with clinical findings. Altogether, the Super-CTPOD test system was shown to be a unique combination of validity, low variation, capacity, efficiency, reliability, productivity, economy, ease of operation, and compact size.

Determination of Steady-State Adhesive Wear Rate

2005 ◽  
Author(s):  
L. J. Yang
Keyword(s):  
Steady State ◽  
Wear Rate ◽  
Wear Test ◽  
Standard Test ◽  
Test Method ◽  
Testing Time ◽  
Wear Coefficient ◽  
Wear Rates ◽  
Test Methodology

Wear rates obtained from different investigators could vary significantly due to lack of a standard test method. A test methodology is therefore proposed in this paper to enable the steady-state wear rate to be determined more accurately, consistently, and efficiently. The wear test will be divided into four stages: (i) to conduct the transient wear test; (ii) to predict the steady-state wear coefficient with the required sliding distance based on the transient wear data by using Yang’s second wear coefficient equation; (iii) to conduct confirmation runs to obtain the measured steady-state wear coefficient value; and (iv) to convert the steady-state wear coefficient value into a steady-state wear rate. The proposed methodology is supported by wear data obtained previously on aluminium based matrix composite materials. It is capable of giving more accurate steady-state wear coefficient and wear rate values, as well as saving a lot of testing time and labour, by reducing the number of trial runs required to achieve the steady-state wear condition.

scholarly journals Competitive Binding of Bilirubin and Fatty Acid on Serum Albumin Affects Wear of UHMWPE

Lubricants ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 53
Author(s):  
Spencer Fullam ◽  
Jade He ◽  
Caroline S. Scholl ◽  
Thomas M. Schmid ◽  
Markus A. Wimmer
Keyword(s):  
Fatty Acid ◽  
Wear Rate ◽  
Conformational Change ◽  
Total Joint Replacement ◽  
Calf Serum ◽  
Competitive Binding ◽  
Wear Testing ◽  
Molar Ratio ◽  
Wear Rates ◽  
Uhmwpe Wear

Total Joint Replacement (TJR) devices undergo standardized wear testing in mechanical simulators while submerged in a proteinaceous testing solution to mimic the environmental conditions of artificial joints in the human body. Typically, bovine calf serum is used to provide the required protein content. However, due to lot-to-lot variability, an undesirable variance in testing outcome is observed. Based on an earlier finding that yellowish-orange serum color saturation is associated with wear rate, we examined potential sources of this variability, by running a comparative wear test with bilirubin; hemin; and a fatty acid, oleic acid, in the lubricant. All these compounds readily bind to albumin, the most abundant protein in bovine serum. Ultrahigh molecular weight polyethylene (UHMWPE) pins were articulated against CoCrMo discs in a pin-on-disc tribometer, and the UHMWPE wear rates were compared between lubricants. We found that the addition of bilirubin increased wear by 121%, while hemin had a much weaker, insignificant effect. When added at the same molar ratio as bilirubin, the fatty acid tended to reduce wear. Additionally, there was a significant interaction with respect to bilirubin and hemin in that UHMWPE wear rate decreased with increasing fatty acid concentration. We believe the conformational change in albumin by binding bilirubin makes it more likely to form molecular bridges between UHMWPE and the metal counterface, thus increasing adhesive wear. However, fatty acids compete for binding sites on albumin, and can prevent this conformational change. Hence, the protein is stabilized, and the chance for albumin to form bridges is lowered. Ultimately, UHMWPE wear rate is driven by the competitive binding of bilirubin and fatty acid to albumin.

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.

The Effect of Motion Path on the Wear Rate of UHMWPE for Orthopaedic Implants

1999 ◽  
Author(s):  
Jeff A. Sprague ◽  
Willard L. Sauer
Keyword(s):  
Wear Rate ◽  
Wear Test ◽  
Axial Rotation ◽  
Wear Testing ◽  
Motion Path ◽  
Orthopaedic Implant ◽  
Wear Rates ◽  
Nonlinear Motion ◽  
Pin On Disk

Abstract The effect of adding a second axis of motion was investigated for pin-on-disk wear testing of ultra-high-molecular-weight polyethylene (UHMWPE) for orthopaedic implant applications. In addition to linear reciprocation of the UHMWPE or metal disk, axial rotation of the metal or UHMWPE pin was conducted. The added rotation reproduces the cross-shear on the UHMWPE surface that is generated in clinically relevant wear simulator tests and in vivo. The wear rates that result from the multi-axis pin-on-disk tests are significantly higher (one to two orders of magnitude) than those seen in the linear-only tests. This supports the findings of other researchers (Bragdon et al., 1996; McKellop, 1995; Walker et al., 1996; Wang et al. 1997) in that the application of nonlinear motion increases the wear of UHMWPE substantially. This is further validated by the comparison of a hip simulator wear test conducted with three axes of motion — rotation, flexion, and abduction — to a test conducted with two axes of motion — rotation and flexion. The absence of the abduction eliminated a significant degree of nonlinear motion (cross-shear) and, consequently, the wear rate was significantly lower than that seen in the test with abduction.

Wear Characteristics of Conventional Ultrahigh-Molecular-Weight Polyethylene Versus Highly Cross-Linked Polyethylene in Total Ankle Arthroplasty

2018 ◽  
Vol 39 (11) ◽  
pp. 1335-1344 ◽  
Author(s):  
Oliver N. Schipper ◽  
Steven L. Haddad ◽  
Spencer Fullam ◽  
Robin Pourzal ◽  
Markus A. Wimmer
Keyword(s):  
Particle Size ◽  
Wear Rate ◽  
Particle Shape ◽  
Polyethylene Wear ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
Total Ankle Arthroplasty ◽  
Fixed Bearing ◽  
Ankle Arthroplasty ◽  
Ultrahigh Molecular Weight ◽  
The Mean

Background: The aim of this study was to compare the polyethylene wear rate, particle size, and particle shape of primary semiconstrained, fixed-bearing, bone-sparing total ankle arthroplasty using conventional ultrahigh-molecular-weight polyethylene (CPE) versus highly cross-linked polyethylene (HXLPE) by applying a level walking input using a joint simulator. Methods: Two fixed-bearing total ankle replacement systems with different types of polyethylene liners were tested: (1) CPE sterilized in ethylene oxide, and (2) HXLPE sterilized with gas plasma after electron beam irradiation. Three implants for each design underwent wear testing using gravimetric analysis over 5 million simulated walking cycles. A fourth implant was used as a load soak control. Equivalent circle diameter (ECD) and equivalent shape ratio (ESR) were computed to determine particle size and particle shape, respectively. Results: The mean wear rate from 1.5 to 5 million cycles (MC) was 2.0 ± 0.3 mg/MC for HXLPE and 16.7 ± 1.3 mg/MC for CPE ( P < .001). The total number of particles per cycle generated for HXLPE and CPE were 0.17 × 106 particles/cycle and 0.53 × 106 particles/cycle, respectively ( P < .001). The mean ECD of HXLPE particles (0.22 ± 0.11 μm) was significantly smaller than the mean ECD of CPE particles (0.32 ± 0.14 μm) ( P < .001). HXLPE particles were significantly more round than CPE particles ( P < .001). Conclusions: HXLPE liners had a significantly lower wear rate and produced significantly fewer and rounder particles than CPE liners. The results of this study suggest that HXLPE has more favorable wear characteristics for total ankle arthroplasty. Clinical Relevance: Polyethylene wear particles have been linked to osteolysis after total ankle arthroplasty. There is no consensus on the importance of highly cross-linked polyethylene in total ankle arthroplasty with regard to implant wear. This is the first nonindustry study to compare the polyethylene wear rate, particle size, and particle shape of fixed-bearing total ankle arthroplasty conventional polyethylene versus highly cross-linked polyethylene. The lower wear rate and different particle size/morphology of highly cross-linked polyethylene could be beneficial in vivo to decrease osteolysis.

Contact Temperature and Its Effects in an Oscillatory Sliding Contact

1989 ◽  
Vol 111 (1) ◽  
pp. 63-69 ◽  
Author(s):  
F. E. Kennedy ◽  
S. C. Cullen ◽  
J. M. Leroy
Keyword(s):  
Wear Rate ◽  
Polyethylene Wear ◽  
Contact Temperature ◽  
Element Analysis ◽  
Wear Rates ◽  
Transfer Films ◽  
Model Predictions ◽  
The Relationship ◽  
Ultra High Molecular Weight ◽  
Good Agreement

The relationship between contact temperature, friction coefficient, and wear rate was studied here for the case of dry sliding between pin and flat in small amplitude oscillatory motion. In the first part of the study, infrared radiation pyrometry and finite element analysis techniques were used to measure and model surface temperatures in an oscillatory contact. Good agreement was achieved between model predictions and experimental measurements. The model was then applied to an oscillating contact between an ultra-high molecular weight polyethylene pin and a rough stainless steel flat. Temperature predictions for that case were correlated with measured friction coefficients and wear rates. It was found that the polyethylene wear rate decreased as the contact temperature increased. The uniformity and thickness of the transfer films which formed on both counterface and polymer pin were found to be affected by contact temperature. Transfer film behavior was deemed responsible for the influence of contact temperature on wear rate.

Wear simulation of the ProDisc-L disc replacement using adaptive finite element analysis

2007 ◽  
Vol 7 (2) ◽  
pp. 165-173 ◽  
Author(s):  
Jeremy J. Rawlinson ◽  
Karan P. Punga ◽  
Kirk L. Gunsallus ◽  
Donald L. Bartel ◽  
Timothy M. Wright
Keyword(s):  
Finite Element ◽  
Wear Rate ◽  
Axial Load ◽  
Computational Simulation ◽  
Wear Test ◽  
Wear Testing ◽  
Adaptive Finite Element ◽  
Wear Rates ◽  
Specific Loading ◽  
Flexion Extension

Object. An understanding of the wear potential of total disc replacements (TDRs) is critical as these new devices are increasingly introduced into clinical practice. The authors analyzed the wear potential of a ProDisc-L implant using an adaptive finite element (FE) technique in a computational simulation representing a physical wear test. Methods. The framework for calculating abrasive wear, first validated using a model of a total hip replacement (THR), was then used to model the ProDisc-L polyethylene component that is fixed to the inferior endplate and articulates with the rigid superior endplate. Proposed standards for spine wear testing protocols specified the inputs of flexion–extension (6/−3°), lateral bending (± 2°), axial twist (± 1.5°), and axial load (200–1750 N or 600–2000 N) applied to the model through 10 million simulation cycles. The model was calibrated with a wear coefficient determined from an experimental wear test. Implicit FE analyses were then performed for variations in coefficient of friction, polyethylene elastic modulus, radial clearance, and polyethylene component thickness to investigate their effects on wear. Results. Using the initial loading protocol (single-peaked axial load profile of 300–1750 N) from the experimental wear test, the polyethylene wear rate was 9.82 mg per million cycles. When a double-peaked loading profile (600–2000 N) was applied, the wear rate increased to 11.77 mg per million cycles. Parametric design variations produced only small changes in wear rates for this simulation. Conclusions. The chosen design variables had little effect on the resultant wear rates. The comparable wear rate for the THR validation analysis was 16.17 mg per million cycles, indicating that, using this framework, the wear potential of the TDR was equivalent to, if not better, than the THR using joint-specific loading standards.

scholarly journals Results of primary THA using 36 mm femoral heads on first-generation highly cross-linked polyethylene in patients less than 60 years of age: Minimum 10-year follow-ups

2020 ◽  
Vol 28 (1) ◽  
pp. 230949901989644
Author(s):  
Myung-Rae Cho ◽  
Chung-Mu Jun ◽  
Kyung-Tae Kim ◽  
Suk Kyun Song ◽  
Won-Kee Choi
Keyword(s):  
Wear Rate ◽  
First Generation ◽  
Femoral Stem ◽  
Long Term Results ◽  
Harris Hip Score ◽  
Acetabular Cup ◽  
Wear Rates ◽  
Femoral Heads ◽  
The Mean

Purpose: Long-term results of total hip arthroplasty (THA) using highly cross-linked polyethylene (HXLPE) and metal femoral head with more than 10 years of follow-up have already been reported. However, most studies included results with a head size of 28 mm that could affect wear rates. The aim of this study was to evaluate the results of 36-mm metallic femoral heads on first-generation HXLPE in patients less than 60 years of age with a minimum follow-up of 10 years. Methods: Retrospective analysis included 54 cases from 47 patients. The mean age at the time of surgery was 47.22 years and the mean follow-up period was 131.04 months. Porous-coated cementless acetabular cups (Trilolgy®; Zimmer Inc., Warsaw, Indiana, USA) and HXLPE acetabular liners (Longevity®; Zimmer Inc.) were used for all cases. Acetabular cup abduction angles, anteversion angles, and wear rates of liner were measured using polyWare pro 3D distal version 5.10. Results: The average modified Harris hip score at the final follow-up was 88.48 (range 80–96). Average Merle d’Aubigne and Postel score was 15.57 (range 14–18). There was no acetabular cup or femoral stem failing due to aseptic loosening. The average steady-state wear rate determined using radiographs taken at 1 year postoperatively and at the latest follow-up was 0.053 ± 0.025 mm/year. There were no statistically significant differences in liner wear rate with respect to age, variety of the femoral stem, or liner thickness. Conclusion: Results of THA with 36-mm metallic femoral heads on first-generation HXLPE in patients less than 60 years of age were satisfactory.

Highly crosslinked polyethylene wear rates and acetabular component orientation

2018 ◽  
Vol 100-B (7) ◽  
pp. 891-897 ◽  
Author(s):  
M. G. Teeter ◽  
B. A. Lanting ◽  
D. D. Naudie ◽  
R. W. McCalden ◽  
J. L. Howard ◽  
...  
Keyword(s):  
Wear Rate ◽  
Acetabular Component ◽  
Inclination Angle ◽  
Polyethylene Wear ◽  
Safe Zone ◽  
Anteversion Angle ◽  
Median Difference ◽  
Head Penetration ◽  
The Mean ◽  
Acetabular Components

Aims The aim of this study was to determine whether there is a difference in the rate of wear between acetabular components positioned within and outside the ‘safe zones’ of anteversion and inclination angle. Patients and Methods We reviewed 100 hips in 94 patients who had undergone primary total hip arthroplasty (THA) at least ten years previously. Patients all had the same type of acetabular component with a bearing couple which consisted of a 28 mm cobalt-chromium head on a highly crosslinked polyethylene (HXLPE) liner. A supine radiostereometric analysis (RSA) examination was carried out which acquired anteroposterior (AP) and lateral paired images. Acetabular component anteversion and inclination angles were measured as well as total femoral head penetration, which was divided by the length of implantation to determine the rate of polyethylene wear. Results The mean anteversion angle was 19.4° (-15.2° to 48°, sd 11.4°), the mean inclination angle 43.4° (27.3° to 60.5°, sd 6.6°), and the mean wear rate 0.055 mm/year (sd 0.060). Exactly half of the hips were positioned inside the ‘safe zone’. There was no difference (median difference, 0.012 mm/year; p = 0.091) in the rate of wear between acetabular components located within or outside the ‘safe zone’. When compared to acetabular components located inside the ‘safe zone’, the wear rate was no different for acetabular components that only achieved the target anteversion angle (median difference, 0.012 mm/year; p = 0.138), target inclination angle (median difference, 0.013 mm/year; p = 0.354), or neither target (median difference, 0.012 mm/year; p = 0.322). Conclusion Placing the acetabular component within or outside the ‘safe zone’ did not alter the wear rate of HXLPE at long-term follow-up to a level that risked osteolysis. HXLPE appears to be a forgiving bearing material in terms of articular surface wear, but care must still be taken to position the acetabular component correctly so that the implant is stable. Cite this article: Bone Joint J 2018;100-B:891-7.

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