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J Fisher - One of the best experts on this subject based on the ideXlab platform.

  • wear of ceramic on ceramic hip joint replacements under standard and Microseparation conditions with two axes and three axes of rotation
    Orthopaedic Proceedings, 2018
    Co-Authors: M Ali, M Alhajjar, J Fisher, Louise M Jennings
    Abstract:

    IntroductionTranslational surgical mismatch in the centres of rotation of the femoral head and acetabular cup in hip joint replacements can lead to dynamic Microseparation resulting in edge loading contact [1]. Increased wear in retrieved ceramic-on-ceramic bearings has been associated with edge loading [2]. Hip joint simulators were used to replicate increased wear rate, stripe wear and bimodal wear debris size distribution, as seen clinically [3,4]. Recently developed electromechanical simulators are able to comply with the latest international standards, which include three axes of rotation conditions [5]. Previous simulators had applied two axes of rotation under Microseparation conditions [6]. Therefore, the aim of this study was to compare the wear of ceramic-on-ceramic bearings obtained under edge loading due to Microseparation conditions during gait using the same electromechanical hip joint simulator with two axes of rotation and three axes of rotation conditions.Materials and MethodsA six-statio...

  • effect of hip implant positioning on edge loading occurrence and severity
    Journal of Bone and Joint Surgery-british Volume, 2017
    Co-Authors: O O Lancasterjones, M Alhajjar, J Thompson, Graham Isaac, J Fisher
    Abstract:

    Background Many factors contribute to the occurrence of edge-loading conditions in hip replacement; soft tissue tension, surgical position, patient biomechanical variations and type of activities, hip design, etc. The aim of this study was to determine the effect of different levels of rotational and translational surgical positioning of hip replacement bearings on the occurrence and severity of edge-loading and the resultant wear rates. Method The Leeds II Hip-Joint Simulator and 36mm diameter alumina matrix composite ceramic bearings (BIOLOX delta, DePuy Synthes, UK) were used in this study. Different levels of mismatch between the reconstructed rotational centres of the head and the cup were considered (2, 3 and 4mm) in the medial-lateral axis. Two cup inclination angles were investigated; an equivalent to 45 and 65 degrees in-vivo, thus six conditions (n=6 for each condition) were studied in total with three million cycles completed for each condition. The wear of the ceramic-on-ceramic bearings were determined using a microbalance (Mettler Toledo, XP205, UK) and the dynamic Microseparation displacement was measured using a Liner Variable Differential Transformer. Results When a translational joint centre mismatch was coupled with a higher cup inclination angle, the severity of edge-loading increased when compared with the effect of those variables applied individually. Increasing the medial-lateral joint centre mismatch from 2 to 3 to 4mm resulted in increased wear rates under both cup inclination angles, with the 65 degree cup inclination angle having significantly higher wear rate than the cup inclination angle of 45 degree (p=0.02, p=0.02, and p Conclusion The cups with a 45 degree inclination angle showed greater resistance to dynamic Microseparation as a result of joint centre mismatch. This study demonstrated that optimal position should not only consider the rotational position of the acetabular cup but also the relative centres of rotation of the head and the cup. Disclosure John Fisher is a paid consultant to DePuy Synthes. Jonathan Thompson and Graham H. Issac are employees at DePuy Synthes.

  • wear of ceramic on ceramic hip joint replacements under standard and Microseparation conditions with two axes and three axes of rotation
    Journal of Bone and Joint Surgery-british Volume, 2016
    Co-Authors: M Ali, M Alhajjar, J Fisher, Louise M Jennings
    Abstract:

    Introduction Translational surgical mismatch in the centres of rotation of the femoral head and acetabular cup in hip joint replacements can lead to dynamic Microseparation resulting in edge loading contact [1]. Increased wear in retrieved ceramic-on-ceramic bearings has been associated with edge loading [2]. Hip joint simulators were used to replicate increased wear rate, stripe wear and bimodal wear debris size distribution, as seen clinically [3,4]. Recently developed electromechanical simulators are able to comply with the latest international standards, which include three axes of rotation conditions [5]. Previous simulators had applied two axes of rotation under Microseparation conditions [6]. Therefore, the aim of this study was to compare the wear of ceramic-on-ceramic bearings obtained under edge loading due to Microseparation conditions during gait using the same electromechanical hip joint simulator with two axes of rotation and three axes of rotation conditions. Materials and Methods A six-station electromechanical hip joint simulator (ProSim EM13, Simulation Solutions, UK) was set up with 36mm diameter ceramic-on-ceramic (BIOLOX® delta, PINNACLE®, DePuy Synthes, UK) hip replacements. The wear was determined for two million cycles under standard conditions with two axes of rotation conditions (n=6), two million cycles under Microseparation conditions with two axes of rotation conditions (n=6) (Figure 1a), and two million cycles under Microseparation conditions with three axes of rotation conditions (n=6) (Figure 1b). The loading profiles [5,7] comprised of 3kN twin peak loads and 300N swing phase load under standard conditions. The swing phase load was reduced to approximately 70N under Microseparation conditions. Approximately 0.5mm of dynamic Microseparation between the head and the cup was applied in the medial/lateral direction. The components were lubricated with 25% new-born calf serum supplemented with 0.03% sodium azide to minimise bacterial growth. The gravimetric wear rates were compared over two million cycles for each test (XP205, Mettler Toledo, UK). The mean wear rates of the head and cup were calculated with 95% confidence limits and statistical analysis was carried out (t-test) with significance levels taken at p Results Under standard conditions, the mean wear rate of BIOLOX® delta ceramic-on-ceramic bearings was 0.03±0.01 mm3/million cycles. The mean wear rates under Microseparation conditions for two axes and three axes of rotation conditions were 0.14±0.01 mm3/million cycles and 0.14±0.03 mm3/million cycles respectively. There was no statistically significant difference between the wear rates using two axes and three axes of rotation conditions under Microseparation conditions (p=0.86). Stripe wear was observed and wear depth measured on the femoral heads under Microseparation conditions using two axes (Figure 2a) and three axes (Figure 2b) of rotation. Conclusion Higher wear rates were observed under Microseparation compared with standard conditions, as reported in a previous study [6]. Similar wear rates were obtained under Microseparation conditions with two axes and three axes of rotation conditions using the same simulator.

  • effect of Microseparation on contact mechanics in metal on metal hip replacements a finite element analysis
    Journal of Biomedical Materials Research Part B, 2015
    Co-Authors: Feng Liu, S. Williams, J Fisher
    Abstract:

    Some early failures of metal‐on‐metal (MoM) hip replacements associated with elevated wear have caused concerns for the use of this bearing combination. Simulator studies have shown that Microseparation and its associated rim contact and edge loading may produce the most severe wear in MoM bearings. It is generally recognized that this high wear can be attributed to the high contact stress of the head on the rim of the cup. In this study, an improved finite element contact model that incorporates an elastic‐perfectly plastic material property for cobalt‐chrome alloy of the metal bearing was developed in an attempt to provide an accurate prediction of the stress and strain for the rim contact. The effects of the Microseparation displacement (0.1−2 mm), cup inclination angle (25−65°) and cup rim radius (0.5−4 mm) on the contact stress/strain were investigated. The results show that a translational displacement >0.1 mm under a load >0.5 kN can produce a highly concentrated contact stress at the surface of the cup rim which can lead to plastic deformation. This study also suggests that the magnitude of translational displacement was the major factor that determined the severity of the contact conditions and level of stress and strain under Microseparation conditions. Future studies will address the effect of surgical translational and rotational malposition and component design on the magnitude of Microseparation, contact stress and strain and severity of wear. © 2014 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 1312–1319, 2015.

  • wear of novel ceramic on ceramic bearings under adverse and clinically relevant hip simulator conditions
    Journal of Biomedical Materials Research Part B, 2013
    Co-Authors: M Alhajjar, Daniel Delfosse, L M Jennings, Thomas Oberbach, Sabine Begand, J Fisher
    Abstract:

    Further development of ceramic materials for total hip replacement aim to increase fracture toughness and further reduce the incidence of bearing fracture. Edge loading due to translational mal positioning (Microseparation) has replicated stripe wear, wear rates, and bimodal wear debris observed on retrievals. This method has replicated the fracture of early zirconia ceramic-on-ceramic bearings. This has shown the necessity of introducing Microseparation conditions to the gait cycle when assessing the tribological performance of new hip replacement bearings. Two novel ceramic matrix composite materials, zirconia-toughened alumina (ZTA) and alumina-toughened zirconia (ATZ), were developed by Mathys Orthopadie GmbH. In this study, ATZ-on-ATZ and ZTA-on-ZTA bearing combinations were tested and compared with alumina-on-alumina (Al2O3-on-Al2O3) bearings under adverse Microseparation and edge loading conditions using the Leeds II physiological anatomical hip joint simulator. The wear rate (±95% confidence limit) of ZTA-on-ZTA was 0.14 ± 0.10 mm3/million cycles and that of ATZ-on-ATZ was 0.06 ± 0.004 mm3/million cycles compared with a wear rate of 0.74 ± 1.73 mm3/million cycles for Al2O3-on-Al2O3 bearings. Stripe wear was evident on all bearing combinations; however, the stripe formed on the ATZ and ZTA femoral heads was thinner and shallower that that formed on the Al2O3 heads. Posttest phase composition measurements for both ATZ and ZTA materials showed no significant change in the monoclinic zirconia content. ATZ-on-ATZ and ZTA-on-ZTA showed superior wear resistance properties when compared with Al2O3-on-Al2O3 under adverse edge loading conditions. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 101B: 1456–1462, 2013.

Eileen Ingham - One of the best experts on this subject based on the ideXlab platform.

  • High Cup Angle and Microseparation Increase the Wear of Hip Surface Replacements
    Clinical Orthopaedics and Related Research®, 2009
    Co-Authors: Ian J. Leslie, Eileen Ingham, S. Williams, Graham Isaac, John Fisher
    Abstract:

    High wear rates and high patient ion levels have been associated with high (> 55°) cup inclination angles for metal-on-metal surface replacements. Wear rates and patterns have been simulated for ceramic-on-ceramic bearings by applying Microseparation to replicate head offset deficiency. We tested 39-mm metal-on-metal surface replacements (n = 5) in a hip simulator with (A) an increased cup inclination angle of 60° and (B) an increased cup inclination angle and Microseparation over 2 million cycles. (A) resulted in a ninefold increase in wear rate and (B) resulted in a 17-fold increase in wear rate compared to a standard gait condition study. Wear particles produced under Microseparation conditions were larger than those produced under standard conditions but of similar shape (round to oval). The data suggest both head and cup position influence the wear of surface replacements; we believe it likely bearings with high wear either have a high cup inclination angle, an offset deficient head, or a combination of both.

  • Characterisation of wear particles produced by metal on metal and ceramic on metal hip prostheses under standard and Microseparation simulation
    Journal of Materials Science: Materials in Medicine, 2007
    Co-Authors: Christopher Brown, John Fisher, S. Williams, Joanne L Tipper, Eileen Ingham
    Abstract:

    The failure of metal on polyethylene total hip replacements due to wear particle induced osteolysis and late aseptic loosening has focused interest upon alternative bearings, such as metal on metal implants. A recent advance in this field has been the development of a novel ceramic on metal implant. The characteristics of the wear particles generated in this low-wearing bearing have not been previously determined. The aims of this study were to characterise metal wear particles from metal on metal and ceramic on metal hips under standard and adverse (Microseparation) wear conditions. Accurate characterisation of cobalt-chrome wear particles is difficult since the reactive nature of the particles prevents them from being isolated using acids and bases. A method was developed to isolate the metal wear particles using enzymes to digest serum containing lubricants from metal on metal and ceramic on metal hip simulations. High resolution scanning electron microscopy was then used to characterise the wear particles generated by both metal on metal and ceramic on metal implants under standard and Microseparation wear conditions. The wear particles isolated from all simulations had a mean size of less than 50 nm with a rounded and irregular morphology. No significant difference was found between the size of wear particles generated under any conditions.

  • effects of clinically relevant alumina ceramic wear particles on tnf α production by human peripheral blood mononuclear phagocytes
    Biomaterials, 2003
    Co-Authors: A Hatton, J Fisher, Jim Nevelos, J B Matthews, Eileen Ingham
    Abstract:

    The recent introduction of Microseparation of the components of ceramic-on-ceramic hip prostheses during hip simulations has produced clinically relevant wear rates, wear patterns and wear particles. This provided an opportunity to determine the response of primary human peripheral blood mononuclear cells to clinically relevant alumina ceramic wear particles in vitro. Alumina ceramic wear particles were generated in a hip joint simulator under Microseparation conditions. The particles showed a bi-modal size distribution with nanometer sized (5–20nm) and larger particles (0.2–>10μm). The particles were cultured with human peripheral blood mononuclear cells obtained from six different donors at particle volume to cell number ratios of 1, 10, 100 and 500μm3. After 24h incubation the viability of the cells and the levels of TNF-α were determined. The response to the Microseparation wear particles was compared to that of commercially available alumina powder with a uniform morphology and mean size of 0.5μm. All six Donors PBMNC produced significantly elevated levels of TNF-α when stimulated with 100μm3 of the alumina powder per cell. Volumetric concentrations of 10 and 1.0μm3 per cell failed to stimulate a significant response by the cells from any of the six donors. Three of the six Donors PBMNC secreted significantly elevated levels of TNF-α when stimulated with 100μm3 of the Microseparation wear particles, whereas the other three failed to respond to the wear debris at this concentration. All of the Donors PBMNC produced significantly elevated levels of TNF-α when stimulated with 500μm3 of the Microseparation wear particles per cell. Thus, a greater volume of the Microseparation wear particles was required to activate the PBMNC than the alumina powder. This was probably due to the Microseparation wear particles having fewer particles in the critical size range (0.1–1μm) for macrophage activation compared to the alumina powder. It can be concluded that alumina ceramic wear particles generated under Microseparation conditions are capable of inducing osteolytic cytokine production by human mononuclear phagocytes. However, the volumetric concentration of the particles needed to generate this response is extremely high and given the low wear rates (<4mm3 per million cycles) of ceramic-on-ceramic bearings, even under severe Microseparation conditions, it is unlikely that this concentration threshold will be achieved in vivo.

  • wear and deformation of ceramic on polyethylene total hip replacements with joint laxity and swing phase Microseparation
    Proceedings of the Institution of Mechanical Engineers Part H: Journal of Engineering in Medicine, 2003
    Co-Authors: S. Williams, M Butterfield, T D Stewart, Eileen Ingham, M. H. Stone, J Fisher
    Abstract:

    AbstractWear of polyethylene and the resulting wear debris-induced osteolysis remains a major cause of long-term failure in artificial hip joints. There is interest in understanding engineering and clinical conditions that influence wear rates. Fluoroscopic studies have shown separation of the head and the cup during the swing phase of walking due to joint laxity. In ceramic-on-ceramic hips, joint laxity and Microseparation, which leads to contact of the head on the superior rim of the cup, has led to localized damage and increased wear in vivo and in vitro. The aim of this study was to investigate the influence of joint laxity and Microseparation on the wear of ceramic on polyethylene artificial hip joints in an in vitro simulator. Microseparation during the swing phase of the walking cycle produced contact of the ceramic head on the rim of the polyethylene acetabular cup that deformed the softer polyethylene cup. No damage to the alumina ceramic femoral head was found. Under standard simulator condition...

  • wear and deformation of ceramic on polyethylene total hip replacements with joint laxity and swing phase Microseparation
    Proceedings of the Institution of Mechanical Engineers Part H: Journal of Engineering in Medicine, 2003
    Co-Authors: S. Williams, M Butterfield, Eileen Ingham, M. H. Stone, T Stewart, J Fisher
    Abstract:

    Wear of polyethylene and the resulting wear debris-induced osteolysis remains a major cause of long-term failure in artificial hip joints. There is interest in understanding engineering and clinical conditions that influence wear rates. Fluoroscopic studies have shown separation of the head and the cup during the swing phase of walking due to joint laxity. In ceramic-on-ceramic hips, joint laxity and Microseparation, which leads to contact of the head on the superior rim of the cup, has led to localized damage and increased wear in vivo and in vitro. The aim of this study was to investigate the influence of joint laxity and Microseparation on the wear of ceramic on polyethylene artificial hip joints in an in vitro simulator. Microseparation during the swing phase of the walking cycle produced contact of the ceramic head on the rim of the polyethylene acetabular cup that deformed the softer polyethylene cup. No damage to the alumina ceramic femoral head was found. Under standard simulator conditions the volume change of the moderately crosslinked polyethylene cups was 25.6 +/- 5.3 mm3/million cycles and this reduced to 5.6 +/- 4.2 mm3/million cycles under Microseparation conditions. Testing under Microseparation conditions caused the rim of the polyethylene cup to deform locally, possibly due to creep, and the volume change of the polyethylene cup when the head relocated was substantially reduced, possibly due to improved lubrication. Joint laxity may be caused by poor soft tissue tension or migration and subsidence of components. In ceramic-on-polyethylene acetabular cups wear was decreased with a small degree of joint laxity, while in contrast in hard-on-hard alumina bearings, Microseparation accelerated wear. These findings may have significant implications for the choice of fixation systems to be used for different types of bearing couples.

Jim Nevelos - One of the best experts on this subject based on the ideXlab platform.

  • effect of Microseparation and third body particles on dual mobility crosslinked hip liner wear
    Journal of Arthroplasty, 2014
    Co-Authors: Jonathan Netter, Jim Nevelos, Juan C Hermida, Peter C Chen, Darryl D Dlima
    Abstract:

    Large heads have been recommended to reduce the risk of dislocation after total hip arthroplasty. One of the issues with larger heads is the risk of increased wear and damage in thin polyethylene liners. Dual-mobility liners have been proposed as an alternative to large heads. We tested the wear performance of highly crosslinked dual-mobility liners under adverse conditions simulating Microseparation and third-body wear. No measurable increase in polyethylene wear rate was found in the presence of third-body particles. Microseparation induced a small increase in wear rate (2.9mm(3)/million cycles). A finite element model simulating Microseparation in dual-mobility liners was validated using these experimental results. The results of our study indicate that highly crosslinked dual-mobility liners have high tolerance for third-body particles and Microseparation.

  • increased wear in low and high crosslinked polyethylene due to Microseparation of total hip arthroplasty components
    Journal of Bone and Joint Surgery-british Volume, 2013
    Co-Authors: Darryl D Dlima, Jonathan Netter, Juan C Hermida, Peter C Chen, Nikolai Steklov, Jim Nevelos
    Abstract:

    Introduction: Microseparation has resulted in more than ten-fold increase in ceramic-on-ceramic and metal-on-metal bearing wear, and even fracture in a zirconia head [1–4]. However, despite the greater Microseparation reported clinically for metal-on-polyethylene wear, less is known about its potential detrimental effects for this bearing couple. This study was therefore designed to simulate the effects of micromotion using finite element analysis and to validate computational predictions with experimental wear testing. Methods: Experimental wear rates for low and highly crosslinked polyethylene hip liners were obtained from a previously reported conventional hip wear simulator study [5]. A finite element model of the wear simulation for this design was constructed to replicate experimental conditions and to compute the wear coefficients that matched the experimental wear rates. We have previous described out this method of validation for knee wear simulation studies [6,7]. This wear coefficient was used to predict wear in a Dual-Mobility hip component (Fig 1). Dual mobility total hip arthroplasty components, Restoration ADM (Fig 1), with highly crosslinked acetabular liners were experimentally tested: the control group was subjected to wear testing using the ISO 14242-1 waveform on a hip wear simulator. The Microseparation group was subjected to a nominal 0.8 mm lateral Microseparation during the swing phase by engaging lateral force springs and reducing the swing phase vertical force. Results: The wear coefficients that matched experimental wear rates for the low and highly crosslinked polyethylene liners were 4.57×10 −10 and 5.89×10 −11 mm 3 N −1 mm −1 , respectively. Introducing Microseparation in the conventional hip increased the wear rate by 15.59 mm 3 /million cycles in the low crosslinked liner and by 1.12 mm 3 /million cycles in the highly crosslinked liner (Fig 2). Discussion: Microseparation did increase predicted wear rates for the low crosslinked polyethylene liner and supports the hypothesis that Microseparation can adversely affect the wear of hip arthroplasty. However, the predicted and experimental increase for the dual mobility highly crosslinked liners due to Microseparation was low (3.3 mm 3 and 2.9 mm 3 /million cycles, respectively) and below the threshold for clinical relevance. The small increase in wear rate in our study supports the high wear tolerance to wear of a dual-mobility sequentially crosslinked polyethylene liner.

  • effects of clinically relevant alumina ceramic wear particles on tnf α production by human peripheral blood mononuclear phagocytes
    Biomaterials, 2003
    Co-Authors: A Hatton, J Fisher, Jim Nevelos, J B Matthews, Eileen Ingham
    Abstract:

    The recent introduction of Microseparation of the components of ceramic-on-ceramic hip prostheses during hip simulations has produced clinically relevant wear rates, wear patterns and wear particles. This provided an opportunity to determine the response of primary human peripheral blood mononuclear cells to clinically relevant alumina ceramic wear particles in vitro. Alumina ceramic wear particles were generated in a hip joint simulator under Microseparation conditions. The particles showed a bi-modal size distribution with nanometer sized (5–20nm) and larger particles (0.2–>10μm). The particles were cultured with human peripheral blood mononuclear cells obtained from six different donors at particle volume to cell number ratios of 1, 10, 100 and 500μm3. After 24h incubation the viability of the cells and the levels of TNF-α were determined. The response to the Microseparation wear particles was compared to that of commercially available alumina powder with a uniform morphology and mean size of 0.5μm. All six Donors PBMNC produced significantly elevated levels of TNF-α when stimulated with 100μm3 of the alumina powder per cell. Volumetric concentrations of 10 and 1.0μm3 per cell failed to stimulate a significant response by the cells from any of the six donors. Three of the six Donors PBMNC secreted significantly elevated levels of TNF-α when stimulated with 100μm3 of the Microseparation wear particles, whereas the other three failed to respond to the wear debris at this concentration. All of the Donors PBMNC produced significantly elevated levels of TNF-α when stimulated with 500μm3 of the Microseparation wear particles per cell. Thus, a greater volume of the Microseparation wear particles was required to activate the PBMNC than the alumina powder. This was probably due to the Microseparation wear particles having fewer particles in the critical size range (0.1–1μm) for macrophage activation compared to the alumina powder. It can be concluded that alumina ceramic wear particles generated under Microseparation conditions are capable of inducing osteolytic cytokine production by human mononuclear phagocytes. However, the volumetric concentration of the particles needed to generate this response is extremely high and given the low wear rates (<4mm3 per million cycles) of ceramic-on-ceramic bearings, even under severe Microseparation conditions, it is unlikely that this concentration threshold will be achieved in vivo.

  • alumina alumina artificial hip joints part ii characterisation of the wear debris from in vitro hip joint simulations
    Biomaterials, 2002
    Co-Authors: J L Tipper, Eileen Ingham, Robert Streicher, A Hatton, Jim Nevelos, C Doyle, A B Nevelos, J Fisher
    Abstract:

    Until recently it was not possible to reproduce clinically relevant wear rates and wear patterns in in vitro hip joint simulators for alumina ceramic-on-ceramic hip prostheses. The introduction of Microseparation of the prosthesis components into in vitro wear simulations produced clinically relevant wear rates and wear patterns for the first time. The aim of this study was to characterise the wear particles generated from standard simulator testing and Microseparation simulator testing of hot isostatically pressed (HIPed) and non-HIPed alumina ceramic-on-ceramic hip prostheses, and compare these particles to those generated in vivo. Standard simulation conditions produced wear rates of approximately 0.1 mm3 per million cycles for both material types. No change in surface roughness was detected and very few wear features were observed. In contrast, when Microseparation was introduced into the wear simulation, wear rates of between 1.24 (HIPed) and 1.74 mm3 per million cycles (non-HIPed) were produced. Surface roughness increased and a wear stripe often observed clinically on retrieved femoral heads was also reproduced. Under standard simulation conditions only nanometre-sized wear particles (2-27.5 nm) were observed by TEM, and it was thought likely that these particles resulted from relief polishing of the alumina ceramic. However, when Microseparation of the prosthesis components was introduced into the simulation, a bi-modal distribution of particle sizes was observed. The nanometre-sized particles produced by relief polishing were present (1-35nm). however, larger micrometre-sized particles were also observed by both transmission electron microscopy (TEM) (0.021 microm) and scanning electron microscopy (SEM) (0.05-->10 microm). These larger particles were thought to originate from the wear stripe and were produced by trans-granular fracture of the alumina ceramic. In Part I of this study, alumina ceramic wear particles were isolated from the periprosthetic tissues from around Mittelmeier ceramic-on-ceramic hip prostheses. Characterisation of the particles by TEM and SEM revealed a bi-modal size distribution. SEM analysis revealed particles in the 0.05-3.2 microm size range. and TEM revealed particles in the 5-90 nm size range, indicating that Microseparation of the prosthesis components may be a common event in vivo. This study (Part II) has revealed that the introduction of Microseparation of the prosthesis components during the swing phase of the wear simulation reproduced clinically relevant wear rates, wear patterns and wear particles in in vitro hip joint simulators.

  • alumina alumina artificial hip joints part ii characterisation of the wear debris from in vitro hip joint simulations
    Biomaterials, 2002
    Co-Authors: J L Tipper, Eileen Ingham, Robert Streicher, A Hatton, Jim Nevelos, C Doyle, A B Nevelos, J Fisher
    Abstract:

    Abstract Until recently it was not possible to reproduce clinically relevant wear rates and wear patterns in in vitro hip joint simulators for alumina ceramic-on-ceramic hip prostheses . The introduction of Microseparation of the prosthesis components into in vitro wear simulations produced clinically relevant wear rates and wear patterns for the first time. The aim of this study was to characterise the wear particles generated from standard simulator testing and Microseparation simulator testing of hot isostatically pressed (HIPed) and non-HIPed alumina ceramic-on-ceramic hip prostheses, and compare these particles to those generated in vivo. Standard simulation conditions produced wear rates of ≈0.1 mm3 per million cycles for both material types. No change in surface roughness was detected and very few wear features were observed. In contrast, when Microseparation was introduced into the wear simulation, wear rates of between 1.24 (HIPed) and 1.74 mm3 per million cycles (non-HIPed) were produced. Surface roughness increased and a wear stripe often observed clinically on retrieved femoral heads was also reproduced. Under standard simulation conditions only nanometre-sized wear particles (2–27.5  nm) were observed by TEM, and it was thought likely that these particles resulted from relief polishing of the alumina ceramic. However, when Microseparation of the prosthesis components was introduced into the simulation, a bi-modal distribution of particle sizes was observed. The nanometre-sized particles produced by relief polishing were present (1–35  nm), however, larger micrometre-sized particles were also observed by both transmission electron microscopy (TEM) (0.02–1  μm) and scanning electron microscopy (SEM) (0.05–>10  μm). These larger particles were thought to originate from the wear stripe and were produced by trans-granular fracture of the alumina ceramic. In Part I of this study, alumina ceramic wear particles were isolated from the periprosthetic tissues from around Mittelmeier ceramic-on-ceramic hip prostheses. Characterisation of the particles by TEM and SEM revealed a bi-modal size distribution. SEM analysis revealed particles in the 0.05–3.2 μm size range, and TEM revealed particles in the 5–90 nm size range, indicating that Microseparation of the prosthesis components may be a common event in vivo. This study (Part II) has revealed that the introduction of Microseparation of the prosthesis components during the swing phase of the wear simulation reproduced clinically relevant wear rates, wear patterns and wear particles in in vitro hip joint simulators.

J L Tipper - One of the best experts on this subject based on the ideXlab platform.

  • wear of ceramic on ceramic bearings in thrs effect of head size under steep cup inclination angle and Microseparation and edge loading conditions
    Orthopaedic Proceedings, 2012
    Co-Authors: M Alhajjar, S. Williams, J Fisher, J L Tipper, Louise M Jennings
    Abstract:

    INTRODUCTION Ceramic-on-ceramic hip replacements have generated great interest in recent years due to substantial improvements in manufacturing techniques and material properties 1 . Microseparation conditions that could occur due to several clinical factors such as head offset deficiency, medialised cup combined with laxity of soft tissue resulting in a translation malalignment, have been shown to cause edge loading, replicate clinically relevant wear mechanisms 2,3 and increase the wear of ceramic-on-ceramic bearings 3,4 . The aim of this study was to investigate the influence of increasing the femoral head size on the wear of ceramic-on-ceramic bearings under several clinically relevant simulator conditions. MATERIALS AND METHODS The wear of size 28mm and 36mm ceramic-on-ceramic bearings (BIOLOX® Delta , CeramTec, Germany) was determined under different in vitro conditions using the Leeds II hip simulator. For each size bearing, two clinical cup inclination angles were considered, 55° (n=3) and 65° (n=3) for the 28mm bearing and 45° (n=3) and 65° (n=3) for the 36mm bearing. The first two (28mm study) or three (36mm study) million cycles ran under standard gait conditions and a subsequent three million cycles ran under Microseparation conditions. A standard gait cycle included a twin peak load (300N–3000N), extension/flexion (−15°/+30°) and internal/external rotation (±10°). Microseparation 3 was achieved by applying a 0.4–0.5mm medial displacement to the cup relative to the head during the swing phase of the standard gait cycle resulting in edge loading at heel strike. The lubricant was 25% (v/v) new-born calf serum which was changed approximately every 333,000 cycles. The wear volume was ascertained through gravimetric analysis every million cycles. One way ANOVA was performed (significance: p RESULTS AND DISCUSSION The mean wear rate under standard gait conditions was 0.05mm 3 / million cycles for the 28mm bearings and significantly lower (p=0.003) for the 36mm bearings (Figure 1) which could be due to improved lubrication regime. The wear of ceramic-on-ceramic bearings was not influenced by the increase in cup inclination angle for either bearing size (Figure 1). The introduction of Microseparation into the gait cycle resulted in stripe wear on the femoral head with a corresponding wear area at the rim of the acetabular cup and significantly higher wear rates of the ceramic-on-ceramic bearings (Figure 2). The wear rate of BIOLOX® Delta bearings under Microseparation conditions was still low ( 3 /million cycles) compared to the third generation alumina ceramic-on-ceramic bearings (1.84mm 3 /million cycles) 4 under the same adverse conditions. Under Microseparation conditions, the wear rate of size 36mm bearings was significantly higher (p=0.004) than that for size 28mm bearings. This was thought to be due to the larger contact area for the larger bearings and deprived lubrication under edge loading conditions. For both bearing sizes, the combination of both steep cup inclination angles and Microseparation conditions did not increase the wear rates any further compared to Microseparation conditions alone (Figure 3). This study shows the importance of surgical positioning of the femoral head and acetabular cup and the importance of testing new bearing materials and designs using these adverse simulator methods. ACKNOWLEDGEMENT This study was supported by the Furlong Research Charitable Foundation (FRCF) and the National Institute of Health Research (NIHR) as part of a collaboration with the Leeds Musculoskeletal Biomedical Research Unit (LMBRU).

  • effect of cup inclination angle during Microseparation and rim loading on the wear of biolox delta ceramic on ceramic total hip replacement
    Journal of Biomedical Materials Research Part B, 2010
    Co-Authors: M Alhajjar, S. Williams, J Fisher, J L Tipper, Ian Leslie, Louise M Jennings
    Abstract:

    Ceramic-on-ceramic (CoC) bearings in total hip replacements (THRs) have shown low wear volumes under standard gait in hip simulator studies. However, clinical reports have indicated variations in wear rates and formation of stripe-like wear area on the ceramic femoral heads. The aim of this study was to investigate the influence of cup inclination angle and Microseparation on the wear of CoC bearings in THRs. The six station Leeds II Physiological Anatomical Joint Simulator was used to investigate the wear of 28 mm diameter alumina matrix composite ceramic bearings (BIOLOX®delta). It was shown that increasing the cup inclination angle from 55o to 65o had no significant effect on the wear rate of BIOLOX®delta CoC under both standard gait and Microseparation conditions in this in vitro study. Under standard gait conditions, the mean wear rate for both cup inclination angle conditions was very low at 0.05 mm3/million cycles. The introduction of Microseparation to the standard gait cycle increased the mean wear rates to 0.13 mm3/million cycles for the cup inclination angle of 55o and 0.11 mm3/million cycles for that of 65°. The level of increased wear with Microseparation was not dependent on cup angle. A stripe of wear on the head also formed, with corresponding superior rim wear on the cup. The wear rates obtained were low compared to the HIPed third generation alumina ceramic (BIOLOX®forte) tested under the same adverse conditions (1.84 mm3/million cycles). BIOLOX®delta has shown lower wear than previous ceramic materials used in THR under adverse conditions. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010.

  • severe wear and fracture of zirconia heads against alumina inserts in hip simulator studies with Microseparation
    Journal of Arthroplasty, 2003
    Co-Authors: T D Stewart, J L Tipper, Gerard M Insley, Robert Streicher, E Ingham, J Fisher
    Abstract:

    Abstract The wear of zirconia femoral heads against alumina acetabular inserts with swing-phase Microseparation was investigated in a hip joint simulator. Under mild Microseparation conditions, the wear was very low, with an average wear rate of 0.05 mm 3 /million cycles reported over 5 million cycles of testing. However, under severe Microseparation conditions representative of greater joint laxity, the wear rate of zirconia against alumina increased by 2 orders of magnitude, producing severe wear and, in one case, femoral head fracture. The adverse results of this study indicate that the combination of a zirconia femoral head articulating against an alumina acetabular insert is not recommended for clinical use. The results further raise concerns over the suitability of conventional simulators in evaluating the wear of ceramic hip prostheses.

  • long term wear of ceramic matrix composite materials for hip prostheses under severe swing phase Microseparation
    Journal of Biomedical Materials Research Part B, 2003
    Co-Authors: T D Stewart, J L Tipper, Gerard M Insley, Robert Streicher, E Ingham, J Fisher
    Abstract:

    The purpose of this study was to evaluate the long-term wear performance of alumina matrix composite (AMC) heads against alumina matrix composite inserts and alumina matrix composite heads against alumina (Al) inserts with the use of a hip-joint simulator incorporating severe swing phase joint Microseparation. The wear of AMC on Al produced an average wear rate of 0.61 mm3/million cycles over the 5-million-cycle test duration. The wear of AMC on AMC produced an average wear rate of 0.16 mm3/million cycles over the 5-million-cycle test duration. Both the AMC on alumina and AMC on AMC produced significantly lower wear than previously tested HIPed alumina, where an average wear rate of 1.84 mm3/million cycles was reported over 5 million cycles. The wear mechanisms and wear debris of AMC on AMC and AMC on Al were similar to those observed in previous alumina retrieval studies with stripe wear caused by intragranular fracture and wear debris consisting of predominantly uniform 10–20-nm-sized particles and a few irregular particles up to 3 μm in size. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 66B: 567–573, 2003

  • alumina alumina artificial hip joints part ii characterisation of the wear debris from in vitro hip joint simulations
    Biomaterials, 2002
    Co-Authors: J L Tipper, Eileen Ingham, Robert Streicher, A Hatton, Jim Nevelos, C Doyle, A B Nevelos, J Fisher
    Abstract:

    Until recently it was not possible to reproduce clinically relevant wear rates and wear patterns in in vitro hip joint simulators for alumina ceramic-on-ceramic hip prostheses. The introduction of Microseparation of the prosthesis components into in vitro wear simulations produced clinically relevant wear rates and wear patterns for the first time. The aim of this study was to characterise the wear particles generated from standard simulator testing and Microseparation simulator testing of hot isostatically pressed (HIPed) and non-HIPed alumina ceramic-on-ceramic hip prostheses, and compare these particles to those generated in vivo. Standard simulation conditions produced wear rates of approximately 0.1 mm3 per million cycles for both material types. No change in surface roughness was detected and very few wear features were observed. In contrast, when Microseparation was introduced into the wear simulation, wear rates of between 1.24 (HIPed) and 1.74 mm3 per million cycles (non-HIPed) were produced. Surface roughness increased and a wear stripe often observed clinically on retrieved femoral heads was also reproduced. Under standard simulation conditions only nanometre-sized wear particles (2-27.5 nm) were observed by TEM, and it was thought likely that these particles resulted from relief polishing of the alumina ceramic. However, when Microseparation of the prosthesis components was introduced into the simulation, a bi-modal distribution of particle sizes was observed. The nanometre-sized particles produced by relief polishing were present (1-35nm). however, larger micrometre-sized particles were also observed by both transmission electron microscopy (TEM) (0.021 microm) and scanning electron microscopy (SEM) (0.05-->10 microm). These larger particles were thought to originate from the wear stripe and were produced by trans-granular fracture of the alumina ceramic. In Part I of this study, alumina ceramic wear particles were isolated from the periprosthetic tissues from around Mittelmeier ceramic-on-ceramic hip prostheses. Characterisation of the particles by TEM and SEM revealed a bi-modal size distribution. SEM analysis revealed particles in the 0.05-3.2 microm size range. and TEM revealed particles in the 5-90 nm size range, indicating that Microseparation of the prosthesis components may be a common event in vivo. This study (Part II) has revealed that the introduction of Microseparation of the prosthesis components during the swing phase of the wear simulation reproduced clinically relevant wear rates, wear patterns and wear particles in in vitro hip joint simulators.

Robert Streicher - One of the best experts on this subject based on the ideXlab platform.

  • severe wear and fracture of zirconia heads against alumina inserts in hip simulator studies with Microseparation
    Journal of Arthroplasty, 2003
    Co-Authors: T D Stewart, J L Tipper, Gerard M Insley, Robert Streicher, E Ingham, J Fisher
    Abstract:

    Abstract The wear of zirconia femoral heads against alumina acetabular inserts with swing-phase Microseparation was investigated in a hip joint simulator. Under mild Microseparation conditions, the wear was very low, with an average wear rate of 0.05 mm 3 /million cycles reported over 5 million cycles of testing. However, under severe Microseparation conditions representative of greater joint laxity, the wear rate of zirconia against alumina increased by 2 orders of magnitude, producing severe wear and, in one case, femoral head fracture. The adverse results of this study indicate that the combination of a zirconia femoral head articulating against an alumina acetabular insert is not recommended for clinical use. The results further raise concerns over the suitability of conventional simulators in evaluating the wear of ceramic hip prostheses.

  • long term wear of ceramic matrix composite materials for hip prostheses under severe swing phase Microseparation
    Journal of Biomedical Materials Research Part B, 2003
    Co-Authors: T D Stewart, J L Tipper, Gerard M Insley, Robert Streicher, E Ingham, J Fisher
    Abstract:

    The purpose of this study was to evaluate the long-term wear performance of alumina matrix composite (AMC) heads against alumina matrix composite inserts and alumina matrix composite heads against alumina (Al) inserts with the use of a hip-joint simulator incorporating severe swing phase joint Microseparation. The wear of AMC on Al produced an average wear rate of 0.61 mm3/million cycles over the 5-million-cycle test duration. The wear of AMC on AMC produced an average wear rate of 0.16 mm3/million cycles over the 5-million-cycle test duration. Both the AMC on alumina and AMC on AMC produced significantly lower wear than previously tested HIPed alumina, where an average wear rate of 1.84 mm3/million cycles was reported over 5 million cycles. The wear mechanisms and wear debris of AMC on AMC and AMC on Al were similar to those observed in previous alumina retrieval studies with stripe wear caused by intragranular fracture and wear debris consisting of predominantly uniform 10–20-nm-sized particles and a few irregular particles up to 3 μm in size. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 66B: 567–573, 2003

  • alumina alumina artificial hip joints part ii characterisation of the wear debris from in vitro hip joint simulations
    Biomaterials, 2002
    Co-Authors: J L Tipper, Eileen Ingham, Robert Streicher, A Hatton, Jim Nevelos, C Doyle, A B Nevelos, J Fisher
    Abstract:

    Until recently it was not possible to reproduce clinically relevant wear rates and wear patterns in in vitro hip joint simulators for alumina ceramic-on-ceramic hip prostheses. The introduction of Microseparation of the prosthesis components into in vitro wear simulations produced clinically relevant wear rates and wear patterns for the first time. The aim of this study was to characterise the wear particles generated from standard simulator testing and Microseparation simulator testing of hot isostatically pressed (HIPed) and non-HIPed alumina ceramic-on-ceramic hip prostheses, and compare these particles to those generated in vivo. Standard simulation conditions produced wear rates of approximately 0.1 mm3 per million cycles for both material types. No change in surface roughness was detected and very few wear features were observed. In contrast, when Microseparation was introduced into the wear simulation, wear rates of between 1.24 (HIPed) and 1.74 mm3 per million cycles (non-HIPed) were produced. Surface roughness increased and a wear stripe often observed clinically on retrieved femoral heads was also reproduced. Under standard simulation conditions only nanometre-sized wear particles (2-27.5 nm) were observed by TEM, and it was thought likely that these particles resulted from relief polishing of the alumina ceramic. However, when Microseparation of the prosthesis components was introduced into the simulation, a bi-modal distribution of particle sizes was observed. The nanometre-sized particles produced by relief polishing were present (1-35nm). however, larger micrometre-sized particles were also observed by both transmission electron microscopy (TEM) (0.021 microm) and scanning electron microscopy (SEM) (0.05-->10 microm). These larger particles were thought to originate from the wear stripe and were produced by trans-granular fracture of the alumina ceramic. In Part I of this study, alumina ceramic wear particles were isolated from the periprosthetic tissues from around Mittelmeier ceramic-on-ceramic hip prostheses. Characterisation of the particles by TEM and SEM revealed a bi-modal size distribution. SEM analysis revealed particles in the 0.05-3.2 microm size range. and TEM revealed particles in the 5-90 nm size range, indicating that Microseparation of the prosthesis components may be a common event in vivo. This study (Part II) has revealed that the introduction of Microseparation of the prosthesis components during the swing phase of the wear simulation reproduced clinically relevant wear rates, wear patterns and wear particles in in vitro hip joint simulators.

  • alumina alumina artificial hip joints part ii characterisation of the wear debris from in vitro hip joint simulations
    Biomaterials, 2002
    Co-Authors: J L Tipper, Eileen Ingham, Robert Streicher, A Hatton, Jim Nevelos, C Doyle, A B Nevelos, J Fisher
    Abstract:

    Abstract Until recently it was not possible to reproduce clinically relevant wear rates and wear patterns in in vitro hip joint simulators for alumina ceramic-on-ceramic hip prostheses . The introduction of Microseparation of the prosthesis components into in vitro wear simulations produced clinically relevant wear rates and wear patterns for the first time. The aim of this study was to characterise the wear particles generated from standard simulator testing and Microseparation simulator testing of hot isostatically pressed (HIPed) and non-HIPed alumina ceramic-on-ceramic hip prostheses, and compare these particles to those generated in vivo. Standard simulation conditions produced wear rates of ≈0.1 mm3 per million cycles for both material types. No change in surface roughness was detected and very few wear features were observed. In contrast, when Microseparation was introduced into the wear simulation, wear rates of between 1.24 (HIPed) and 1.74 mm3 per million cycles (non-HIPed) were produced. Surface roughness increased and a wear stripe often observed clinically on retrieved femoral heads was also reproduced. Under standard simulation conditions only nanometre-sized wear particles (2–27.5  nm) were observed by TEM, and it was thought likely that these particles resulted from relief polishing of the alumina ceramic. However, when Microseparation of the prosthesis components was introduced into the simulation, a bi-modal distribution of particle sizes was observed. The nanometre-sized particles produced by relief polishing were present (1–35  nm), however, larger micrometre-sized particles were also observed by both transmission electron microscopy (TEM) (0.02–1  μm) and scanning electron microscopy (SEM) (0.05–>10  μm). These larger particles were thought to originate from the wear stripe and were produced by trans-granular fracture of the alumina ceramic. In Part I of this study, alumina ceramic wear particles were isolated from the periprosthetic tissues from around Mittelmeier ceramic-on-ceramic hip prostheses. Characterisation of the particles by TEM and SEM revealed a bi-modal size distribution. SEM analysis revealed particles in the 0.05–3.2 μm size range, and TEM revealed particles in the 5–90 nm size range, indicating that Microseparation of the prosthesis components may be a common event in vivo. This study (Part II) has revealed that the introduction of Microseparation of the prosthesis components during the swing phase of the wear simulation reproduced clinically relevant wear rates, wear patterns and wear particles in in vitro hip joint simulators.

  • long term wear of hiped alumina on alumina bearings for thr under Microseparation conditions
    Journal of Materials Science: Materials in Medicine, 2001
    Co-Authors: T Stewart, Eileen Ingham, J L Tipper, Robert Streicher, J Fisher
    Abstract:

    The long term wear and wear debris generated in HIPed alumina on alumina bearings for hip prostheses with Microseparation in vitro is compared to standard simulator conditions and ex vivo specimens. Microseparation studies were completed to five million cycles at two severity levels in attempts to rigorously evaluate the long-term tribological performance of the bearings. During the first million cycles (bedding-in) of the Microseparation tests characteristic stripe wear was observed on all of the femoral heads with a matching area on the rim of the acetabular inserts. Under mild Microseparation conditions an average wear rate of 0.55 mm3/million cycles was observed during the initial million cycles which reduced to a steady state level of 0.1 mm3/million cycles. Under more severe conditions an average wear rate of 4.0 mm3/million cycles was observed during bedding-in which reduced to a steady state level of 1.3 mm3/million cycles. These compare to a bedding-in wear rate of 0.11 mm3/million cycles and steady-state wear rate of 0.05 mm3/million cycles for the same material under normal simulation with no Microseparation. Furthermore, under Microseparation the wear mechanisms and wear debris were similar to those observed in previous alumina retrieval studies with debris ranging from 10 nm to 1 μm in size.