scholarly journals Does diametrical clearance influence the wear of Pinnacle hip implants?

2020 ◽  
Vol 9 (8) ◽  
pp. 515-523 ◽  
Author(s):  
Sean Bergiers ◽  
Harry Hothi ◽  
Johann Henckel ◽  
Antti Eskelinen ◽  
John Skinner ◽  
...  
Keyword(s):  
Volumetric Wear ◽  
Wear Performance ◽  
Wear Rates ◽  
Manufacturing Tolerance ◽  
Metal On Metal ◽  
Hip Arthroplasties ◽  
The Relationship ◽  
Spearman’S Correlation ◽  
Film Lubrication ◽  
Fluid Film Lubrication

Aims The optimum clearance between the bearing surfaces of hip arthroplasties is unknown. Theoretically, to minimize wear, it is understood that clearances must be low enough to maintain optimal contact pressure and fluid film lubrication, while being large enough to allow lubricant recovery and reduce contact patch size. This study aimed to identify the relationship between diametrical clearance and volumetric wear, through the analysis of retrieved components. Methods A total of 81 metal-on-metal Pinnacle hips paired with 12/14 stems were included in this study. Geometrical analysis was performed on each component, using coordinate and roundness measuring machines. The relationship between their as-manufactured diametrical clearance and volumetric wear was investigated. The Mann-Whitney U test and unpaired t-test were used, in addition to calculating the non-parametric Spearman's correlation coefficient, to statistically evaluate the acquired data. Results The hips in this study were found to have had a median unworn diametrical clearance of 90.31 μm (interquartile range (IQR) 77.59 to 97.40); 32% (n = 26) were found to have been below the manufacturing tolerance. There was no correlation found between clearance and bearing (rs = -0.0004, p = 0.997) or taper (rs = 0.0048, p = 0.966) wear rates. The wear performance of hips manufactured within and below these specifications was not significantly different (bearing: p = 0.395; taper: p = 0.653). Pinnacles manufactured from 2007 onwards had a greater prevalence of bearing clearance below tolerance (p = 0.004). Conclusion The diametrical clearance of Pinnacle hips did not influence their wear performance, even when below the manufacturing tolerance. The optimum clearance for minimizing hip implant wear remains unclear. Cite this article: Bone Joint Res 2020;9(8):515–523.

scholarly journals Wear performance of retrieved metal-on-metal Pinnacle hip arthroplasties implanted before and after 2007

2018 ◽  
Vol 7 (11) ◽  
pp. 595-600 ◽  
Author(s):  
S. Bergiers ◽  
H. S. Hothi ◽  
J. Henckel ◽  
A. Eskelinen ◽  
J. Skinner ◽  
...  
Keyword(s):  
Linear Regression Models ◽  
Wear Performance ◽  
Wear Rates ◽  
Female Patients ◽  
High Profile ◽  
Metal On Metal ◽  
Significant Difference ◽  
Before And After ◽  
Hip Arthroplasties ◽  
Mean Time

ObjectivesPrevious studies have suggested that metal-on-metal (MoM) Pinnacle (DePuy Synthes, Warsaw, Indiana) hip arthroplasties implanted after 2006 exhibit higher failure rates. This was attributed to the production of implants with reduced diametrical clearances between their bearing surfaces, which, it was speculated, were outside manufacturing tolerances. This study aimed to better understand the performance of Pinnacle Systems manufactured before and after this event.MethodsA total of 92 retrieved MoM Pinnacle hips were analyzed, of which 45 were implanted before 2007, and 47 from 2007 onwards. The ‘pre-2007’ group contained 45 implants retrieved from 21 male and 24 female patients, with a median age of 61.3 years (interquartile range (IQR) 57.1 to 65.5); the ‘2007 onwards’ group contained 47 implants retrieved from 19 male and 28 female patients, with a median age of 61.8 years (IQR 58.5 to 67.8). The volume of material lost from their bearing and taper surfaces was measured using coordinate and roundness measuring machines. These outcomes were then compared statistically using linear regression models, adjusting for potentially confounding factors.ResultsThere was no significant difference between the taper and bearing wear rates of the ‘pre-2007’ and ‘2007 onwards’ groups (p = 0.67 and p = 0.39, respectively). Pinnacles implanted from 2007 onwards were revised after a mean time of 50 months, which was significantly earlier than the ‘pre-2007’ hips (96 months) (p < 0.001). A reduction in the time to revision was present year on year from 2003 to 2011.ConclusionWe found no difference in the wear rate of these implants based on the year of implantation. The ‘pre-2007’ hips had a two-fold greater time to revision than those implanted after 2007; this may be due to the increased surveillance of MoM hips following UK regulatory advice and several high-profile failures. Interestingly, we observed a decreasing trend in the mean time to revision every year from 2003 onwards. Cite this article: S. Bergiers, H. S. Hothi, J. Henckel, A. Eskelinen, J. Skinner, A. Hart. Wear performance of retrieved metal-on-metal Pinnacle hip arthroplasties implanted before and after 2007. Bone Joint Res 2018;7:595–600. DOI: 10.1302/2046-3758.711.BJR-2018-0143.R1.

scholarly journals Aseptic lymphocyte-dominated vasculitis-associated lesions are related to changes in metal ion handling in the joint capsules of metal-on-metal hip arthroplasties

2018 ◽  
Vol 7 (6) ◽  
pp. 388-396 ◽  
Author(s):  
D. J. Langton ◽  
R. P. Sidaginamale ◽  
T. J. Joyce ◽  
J. G. Bowsher ◽  
J. P. Holland ◽  
...  
Keyword(s):  
Metal Ion ◽  
Fluid Collection ◽  
Joint Fluid ◽  
Volumetric Wear ◽  
Wear Rates ◽  
Ion Concentrations ◽  
Associated Lesions ◽  
Metal On Metal ◽  
Hip Arthroplasties ◽  
Co Concentrations

Objectives We have encountered patients who developed large joint fluid collections with massive elevations in chromium (Cr) and cobalt (Co) concentrations following metal-on-metal (MoM) hip arthroplasties. In some cases, retrieval analysis determined that these ion concentrations could not be explained simply by the wear rates of the components. We hypothesized that these effects may be associated with aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). Patients and Methods We examined the influence of the ALVAL grade on synovial fluid Co and Cr concentrations following adjustment for patient and device variables, including volumetric wear rates. Initially restricting the analysis to include only patients with one MoM hip resurfacing device, we performed multiple regression analyses of prospectively collected data. We then repeated the same statistical approach using results from a larger cohort with different MoM designs, including total hip arthroplasties. Results In the resurfacing cohort (n = 76), the statistical modelling indicated that the presence of severe ALVAL and a large fluid collection were associated with greater joint fluid Co concentrations after adjustment for volumetric wear rates (p = 0.005). These findings were replicated in the mixed implant group (n = 178), where the presence of severe ALVAL and a large fluid collection were significantly associated with greater fluid Co concentrations (p < 0.001). Conclusion The development of severe ALVAL is associated with elevations in metal ion concentrations far beyond those expected from the volumetric loss from the prosthetic surfaces. This finding may aid the understanding of the sequence of events leading to soft-tissue reactions following MoM hip arthroplasties. Cite this article: D. J. Langton, R. P. Sidaginamale, T. J. Joyce, J. G. Bowsher, J. P. Holland, D. Deehan, A. V. F. Nargol, S. Natu. Aseptic lymphocyte-dominated vasculitis-associated lesions are related to changes in metal ion handling in the joint capsules of metal-on-metal hip arthroplasties. Bone Joint Res 2018;7:388–396. DOI: 10.1302/2046-3758.76.BJR-2018-0037.

Alternative Bearing Couples in Total Hip Replacements: Solutions for Young Patients

2003 ◽  
Vol 13 (2_suppl) ◽  
pp. 31-35 ◽  
Author(s):  
J. Fisher ◽  
E. Ingham ◽  
M.H. Stone
Keyword(s):  
Polyethylene Wear ◽  
Young Patients ◽  
Volumetric Wear ◽  
Wear Rates ◽  
Total Hip Replacements ◽  
Metal On Metal ◽  
Hip Replacements ◽  
Gamma Irradiated ◽  
Ceramic On Ceramic

There is now considerable clinical concern about the effect of polyethylene wear debris induced osteolysis in long term failure of hip replacements. This paper compares the wear of stabilised and crosslinked polyethylene to alternative hard on hard bearings. The volumetric wear rates of stabilised and moderately crosslinked polyethylene 50 to 35 mm3/million cycles were less than previously reported for historical gamma irradiated in air polyethylene, but still of a level that in the long term could cause osteolysis. The moderately crosslinked polyethylene produced less wear than non-crosslinked polyethylene, but particles were smaller and more reactive resulting in little change in the osteolytic potential. Alumina ceramic on ceramic produced substantially less wear and osteolytic potential. Metal on metal also produced less wear than polyethylene but the particles adversely influence cell viability.

Clinical Wear Performance of Metal-on-Metal Hip Arthroplasties

2009 ◽  
pp. 144-144-13 ◽  
Author(s):  
CB Rieker ◽  
P Köttig ◽  
R Schön ◽  
M Windler ◽  
UP Wyss
Keyword(s):  
Wear Performance ◽  
Metal On Metal ◽  
Hip Arthroplasties

Comparison of the Bearing Performance of Normal and Artificial Human Joints

1973 ◽  
Vol 95 (3) ◽  
pp. 333-339 ◽  
Author(s):  
P. S. Walker ◽  
B. L. Gold
Keyword(s):  
Hip Joints ◽  
Artificial Joints ◽  
Metal On Metal ◽  
Joint Lubrication ◽  
Artificial Hip ◽  
Normal Human ◽  
Artificial Hip Joints ◽  
Human Joints ◽  
Film Lubrication ◽  
Fluid Film Lubrication

A comparison is made between the lubrication mechanisms believed to occur in normal human hip joints, and artificial hip joints. A review of the literature and some new experimental data is used to highlight many of the characteristics of human joint lubrication. Specimens of artificial joints removed from patients after various periods of service were studied, and deductions made about the modes of lubrication and wear. Both metal-on-metal and metal-on-plastic joints were considered. It was concluded that human joints operated mainly by fluid film lubrication while artificial joints displayed principally boundary lubrication.

Effect of Acetabular Cup Design on the Tribology of Metal-on-Metal Hip Resurfacing Replacements: A Contact Mechanics and Elastohydrodynamic Lubrication Study

2005 ◽  
Author(s):  
I. Udofia ◽  
F. Liu ◽  
Z. Jin ◽  
P. Roberts ◽  
P. Grigoris
Keyword(s):  
Contact Mechanics ◽  
Wall Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Hip Resurfacing ◽  
Fluid Film ◽  
Acetabular Cup ◽  
Metal On Metal ◽  
Film Lubrication ◽  
Fluid Film Lubrication

The tribology of metal-on-metal (MOM) hip resurfacing prostheses has been investigated in this study, with particular consideration of the effect of prosthesis design (cup wall thickness and clearance) on the contact mechanics and elastohydrodynamic lubrication (EHL) of these man-made bearings. Two commercially available MOM hip resurfacings, which differ mainly in cup-wall thickness and diametral clearance, were investigated. Finite element contact mechanics and lubrication analyses were carried out on the two MOM hip resurfacing designs. It was found that the thinner acetabular cup with a the relatively smaller clearance resulted in lower contact and hydrodynamic pressure predictions, and a significant increase in the predicted lubricant film thickness at the bearing surfaces. This was attributed to the increase in contact area, conformity between the cup and ball and to the increased influence of the underlying non-metallic structures such as bone and cement, which enhanced the elasticity of the thin acetabular cup. It was shown that full fluid-film lubrication was possible in MOM hip resurfacings during the walking cycle with the small clearance and thin cup-wall thickness model. The importance of the design and manufacturing parameters on the tribological performance of MOM hip resurfacings is highlighted in this study, particularly in promoting fluid film lubrication as a means to further reduce wear at the bearing surfaces.

scholarly journals Nasal Morphology and Its Correlation to Craniofacial Morphology in Lateral Cephalometric Analysis

2021 ◽  
Vol 18 (6) ◽  
pp. 3064
Author(s):  
Agnieszka Jankowska ◽  
Joanna Janiszewska-Olszowska ◽  
Katarzyna Grocholewicz
Keyword(s):  
Soft Tissue ◽  
Nasal Bone ◽  
Correlation Coefficients ◽  
Craniofacial Morphology ◽  
Base Angle ◽  
Nasolabial Angle ◽  
Orthodontic Patients ◽  
Nose Shape ◽  
The Relationship ◽  
Spearman’S Correlation

Nose shape, size, and inclination influence facial appearance, but few studies concern the relationship between the nasal profile and craniofacial structures. The objective of this study was to analyze association of nasal cephalometric variables with skeletal structures, age, and sex. Cephalometric and nasal analysis was performed in 386 Polish orthodontic patients (aged 9–25 years). Student t-test and Mann–Whitney test were used to compare quantitative variables and Pearson’s or Spearman’s correlation coefficients—to find correlations. Soft tissue facial convexity angle correlates to Holdaway ratio, ANB (A-Nasion-B), and Wits appraisal. Nasal dorsum axis, nose length, nose depth (1) and nose depth (2), nose hump, lower dorsum convexity, and columella convexity increase with age. Nasal base angle, nasolabial angle, nasomental angle, soft tissue facial convexity and nasal bone angle decrease with age. Nasal base angle and nasomental angle are smaller in females. Thus, a relationship exists between nasal morphology and sagittal jaw configuration. Nasal parameters significantly change with age. Sexual dimorphism characterizes nasal bone angle and nasomental angle.

scholarly journals Sliding Wear of Conventional and Suspension Sprayed Nanocomposite WC-Co Coatings: An Invited Review

2021 ◽  
Author(s):  
R. Ahmed ◽  
O. Ali ◽  
C. C. Berndt ◽  
A. Fardan
Keyword(s):  
Wear Rate ◽  
Thermal Spray ◽  
Sliding Wear ◽  
Failure Modes ◽  
Thermal Spray Coatings ◽  
Annual Growth Rate ◽  
Total Energy Consumption ◽  
Wear Performance ◽  
Wear Rates ◽  
Spray Coatings

AbstractThe global thermal spray coatings market was valued at USD 10.1 billion in 2019 and is expected to grow at a compound annual growth rate of 3.9% from 2020 to 2027. Carbide coatings form an essential segment of this market and provide cost-effective and environmental friendly tribological solutions for applications in aerospace, industrial gas turbine, automotive, printing, oil and gas, steel, and pulp and paper industries. Almost 23% of the world’s total energy consumption originates from tribological contacts. Thermal spray WC-Co coatings provide excellent wear resistance for industrial applications in sliding and rolling contacts. Some of these applications in abrasive, sliding and erosive conditions include sink rolls in zinc pots, conveyor screws, pump housings, impeller shafts, aircraft flap tracks, cam followers and expansion joints. These coatings are considered as a replacement of the hazardous chrome plating for tribological applications. The microstructure of thermal spray coatings is however complex, and the wear mechanisms and wear rates vary significantly when compared to cemented WC-Co carbides or vapour deposition WC coatings. This paper provides an expert review of the tribological considerations that dictate the sliding wear performance of thermal spray WC-Co coatings. Structure–property relationships and failure modes are discussed to grasp the design aspects of WC-Co coatings for tribological applications. Recent developments of suspension sprayed nanocomposite coatings are compared with conventional coatings in terms of performance and failure mechanisms. The dependency of coating microstructure, binder material, carbide size, fracture toughness, post-treatment and hardness on sliding wear performance and test methodology is discussed. Semiempirical mathematical models of wear rate related to the influence of tribological test conditions and coating characteristics are analysed for sliding contacts. Finally, advances for numerical modelling of sliding wear rate are discussed.

scholarly journals Rolling Wear of Silicon Nitride Bearing Materials

1990 ◽  
Author(s):  
John W. Lucek
Keyword(s):  
Fatigue Life ◽  
Silicon Nitride ◽  
Failure Modes ◽  
Fatigue Testing ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Wear Performance ◽  
Wear Rates ◽  
Bearing Materials

Rolling-contact fatigue test methods were used to measure the wear performance of several silicon nitride materials. Sintered, hot pressed and hot isostatically pressed materials exhibited wear rates ranging over three orders of magnitude. Hot isostatically pressed materials had the lowest wear rates. Despite the disparity in wear performance, all materials tested had useful rolling-contact fatigue lives compared to steel. Fatigue life estimates, failure modes, and rolling wear performance for theses ceramics are compared to M-50 steel. This work highlights the rapid contact stress reductions that occur due to conformal wear in rolling-contact fatigue testing. Candidate bearing materials with unacceptably high wear rates may exhibit useful fatigue lives. Rolling contact bearing materials must possess useful wear and fatigue resistance. Proper performance screening of candidate bearing materials must describe the failure mode, wear rate, and the fatigue life. Guidelines for fatigue testing methods are proposed.

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