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Mathew T. Mathew - One of the best experts on this subject based on the ideXlab platform.
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Hip Implant performance prediction by acoustic emission techniques: a review
Medical & Biological Engineering & Computing, 2020Co-Authors: Ampadi R. Remya, B. Vishwash, Alejandro A. Espinoza Oras, Didem Ozevin, Mathew T. MathewAbstract:Nowadays, acoustic emission (AE) has its applications in various areas, including mechanical, civil, underwater acoustics, and biomedical engineering. It is a non-destructive evaluation (NDE) and a non-intrusive method to detect active damage mechanisms such as crack growth, delamination, and processes such as friction, continuous wear, etc. The application of AE in orthopedics, especially in Hip Implant monitoring, is an emerging research field. This article presents a thorough literature review associated with the implementation of acoustic emission as a diagnostic tool for total Hip replacement (THR) Implants. Structural health monitoring of an Implant via acoustic emission and vibration analysis is an evolving research area in the field of biomedical engineering. A review of the literature reveals a lack of reliable, non-invasive, and non-traumatic early warning methods to evaluate Implant loosening that can help to identify patients at risk for osteolysis prior to Implant failure. Developing an intelligent acoustic emission technique with excellent condition monitoring capabilities will be an achievement of great importance that fills the gaps or drawbacks associated with osteolysis/Implant failure. Graphical abstract
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wear mapping based prediction methods for improved fretting corrosion performance of Hip Implant modular interfaces
Orthopaedic Proceedings, 2018Co-Authors: Dmitry Royhman, Nadim J Hallab, Joshua J Jacobs, Mathew T. MathewAbstract:Modern Hip Implants feature a modular design, whereby the individual components of the Implant are assembled during the surgery. Increased reported failure rates associated with the utilization of modular junctions have raised many clinical concerns about the increased release of metal ions/debris leading to adverse local tissue reactions. Implant materials are subject to a myriad of mechanical motion and forces, and varying electrochemical conditions and pH changes from the surrounding environment. To date, no studies have attempted to model the collected data in order to predict the performance of the materials so that precautions can be taken before the problem reaches the critical stage. This study reports the effects of pH variation, displacement variation, and load variation on the mechanical and corrosion behavior of the Hip Implant modular junction system, tested with a custom-built fretting-corrosion apparatus. The main objective of this study is to combine the complete data set of the in-vitro e...
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In vitro simulation of fretting-corrosion in Hip Implant modular junctions: The influence of pH
Medical Engineering and Physics, 2018Co-Authors: Dmitry Royhman, Megha Patel, Nadim J Hallab, Joshua J Jacobs, Markus A Wimmer, Mathew T. MathewAbstract:Background: The fretting-corrosion behavior of mixed metal contacts is affected by various mechanical and electrochemical parameters. Crevice conditions at the junction and patient-specific pathologies can affect the pH of the prosthetic environment. The main objective of this study is to understand the effect of pH variation at the stem/head junction of the Hip Implant under fretting corrosion exposure. We hypothesized that pH will have a significant influence on the fretting-corrosion behavior Hip Implant modular junctions. Materials and methods: A custom-made setup was used to evaluate the fretting corrosion behavior of Hip Implant modular junctions. A Newborn calf serum solution (30 g/L protein content) was used to simulate the synovial fluid environment. A sinusoidal fretting motion, with a displacement amplitude of +50 µm, was applied to the Ti alloy rod. The effects of pathology driven, periprosthetic pH variation were simulated at four different pH levels (3.0, 4.5, 6.0 and 7.6). Electrochemical and mechanical properties were evaluated before, during, and after the applied fretting motion. Results: The impedance of the system was increased in response to the fretting motion. The hysteresis tangential load/displacement behavior was not affected by pH level. The worn surfaces of CoCrMo pins exhibited the presence of tribolayer or organic deposits, in the pH 4.5 group, which may explain the lower drop in potential and mass loss observed in that group. Mechanically dominated wear mechanisms, namely, adhesive wear was shown in the pH 7.6 group, which may account for a higher potential drop and metal content loss. Conclusions: This study suggests that the fretting-corrosion mechanisms in Hip Implant are affected by the pH levels of the surrounding environment and patient-specific factors.
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wear mapping based prediction methods for improved fretting corrosion performance of Hip Implant modular interfaces
Journal of Bone and Joint Surgery-british Volume, 2017Co-Authors: Dmitry Royhman, Nadim J Hallab, Joshua J Jacobs, Mathew T. MathewAbstract:Modern Hip Implants feature a modular design, whereby the individual components of the Implant are assembled during the surgery. Increased reported failure rates associated with the utilization of modular junctions have raised many clinical concerns about the increased release of metal ions/debris leading to adverse local tissue reactions. Implant materials are subject to a myriad of mechanical motion and forces, and varying electrochemical conditions and pH changes from the surrounding environment. To date, no studies have attempted to model the collected data in order to predict the performance of the materials so that precautions can be taken before the problem reaches the critical stage. This study reports the effects of pH variation, displacement variation, and load variation on the mechanical and corrosion behavior of the Hip Implant modular junction system, tested with a custom-built fretting-corrosion apparatus. The main objective of this study is to combine the complete data set of the in-vitro experiments to create fretting-corrosion wear maps that can predict the dangerous domains of the Hip Implant modular system. For each test, the flat portions of two CoCrMo pins were loaded perpendicularly against a Ti6Al4V Rod (Ti alloy) in a Flat-on-flat configuration in a simulated synovial fluid in order to simulate the modular Hip Implant system. A schematic diagram of contact conditions is presented in Figure 1. A sinusoidal displacement was applied onto the rod, which articulated against the CoCrMo alloy pins, at a frequency of 1Hz. The experiential data from the fretting-corrosion tests has been used to create fretting-corrosion maps. The variables incorporated into the maps include: total mass loss, electrochemical destabilization, pH variation, load variation, displacement variation, and visual examination of the wear features of the contact zone. Total mass loss has been estimated via measurement of the simulator fluid by ICP-MS technique. Electrochemical destabilization was evaluated by a single parameter (V Drop ). The electrochemical destabilization of the tribosystem was evaluated by measuring the drop in potential, V Drop (V vs. SCE), resultant from the initiation of the fretting phase. The V Drop refers to the initial cathodic drop in potential in response to the initial onset of fretting motion. The data from the in vitro fretting-corrosion experiments has been combined to create four fretting-corrosion maps (Figures 2A–3D). Partial slip wear features and mechanical behavior was observed at 25µm displacement. 25–150µm displacement amplitudes showed gross slip behavior. Anything larger than 150µm displayed wear features that were indistinguishable from sliding wear. In general, total mass loss and V Drop increased with increasing displacement. Samples that were tested at pH 6.0 or higher showed signs of material transfer and higher V Drop . Finally, there was a general decrease in V Drop with increased applied load and pH. In general, the wears maps were able to offer some predictive validity, however, there were some discrepancies between visual observations and the observed damage parameters. It is possible that other parameters could offer better correlation. Future studies will be conducted to measure other parameters. For figures/tables, please contact authors directly.
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Fretting-corrosion behavior in Hip Implant modular junctions: The influence of friction energy and pH variation
Journal of the Mechanical Behavior of Biomedical Materials, 2016Co-Authors: Dmitry Royhman, Maria J. Runa, Megha Patel, Nadim J Hallab, Joshua J Jacobs, Markus A Wimmer, Mathew T. MathewAbstract:Background: Recently, there has been increasing concern in the orthopedic community over the use of Hip Implant modular devices due to an increasing number of reports of early failure, failure that has been attributed to fretting-corrosion at modular interfaces. Much is still unknown about the electrochemical and mechanical degradation mechanisms associated with the use of such devices. Purpose: Accordingly, the purpose of our study was to develop a methodology for testing the fretting-corrosion behavior of modular junctions. Methods: A fretting-corrosion apparatus was used to simulate the fretting-corrosion conditions of a CoCrMo Hip Implant head on a Ti6Al4V Hip Implant stem. The device features two perpendicularly-loaded CoCrMo pins that articulated against a Ti6Al4V rod. A sinusoidal fretting motion was applied to the rod at various displacement amplitudes (25, 50, 100, 150 and 200 μm) at a constant load of 200 N. Bovine calf serum at two different pH levels (3.0 and 7.6) was used to simulate the fluid environment around the joint. Experiments were conducted in two modes of electrochemical control - free-potential and potentiostatic. Electrochemical impedance spectroscopy tests were done before and after the fretting motion to assess changes in corrosion kinetics. Results: In free potential mode, differences were seen in change in potential as a function of displacement amplitude. In general, VDrop (the drop in potential at the onset of fretting), VFretting, (the average potential during fretting), δVFretting (the change in potential from the onset of fretting to its termination) and VRecovery (the change in potential from the termination of fretting until stabilization) appeared linear at both pH levels, but showed drastic deviation from linearity at 100 μm displacement amplitude. Subsequent EDS analysis revealed a large number of Ti deposits on the CoCrMo pin surfaces. Potentiostatic tests at both pH levels generally showed increasing current with increasing displacement amplitude. Electrochemical impedance spectroscopy measurements from free potential and potentiostatic tests indicated increased levels of resistance of the system after induction of the fretting motion. In free potential tests, the largest increase in impedance was found for the 100 μm group. Conclusions: We conclude that the 100 μm group exhibits deviations from linearity for several parameters, and this was most likely due to adhesive wear between Ti6Al4V and CoCrMo surfaces. Overall, the degradation of the system was dominated by wear at all pH levels, and displacement amplitudes.
Habiba Bougherara - One of the best experts on this subject based on the ideXlab platform.
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Biomechanical optimization of the angle and position for surgical Implantation of a straight short stem Hip Implant.
Medical Engineering & Physics, 2017Co-Authors: Gillian E. Cook, Habiba Bougherara, Saeid Samiezadeh, Zachary Morison, Mina S.r. Aziz, Rad Zdero, Emil H SchemitschAbstract:Conservative Hip Implants preserve healthy bone for revision surgeries and improve physiological loading; however, they have little supporting biomechanical data with respect to their 3D orientation during Implantation. This study endeavored to determine the optimal 3D orientation of a straight short stem Hip Implant within the proximal femur that would yield a stress distribution most similar to an intact femur. Synthetic femurs were Implanted with a stem in one of seven maximum angles or positions and axially loaded, with resultant strain values used to validate a finite element model. Design of experiments was used to analyze the range of potential Implant orientations under three gait cycle loading conditions. A global optimal orientation of 9.14° valgus, 2.49° anteversion, 0.48mm posterior position, and 0.23mm inferior position was found to yield stress distributions most similar to the intact femur across the gait cycle range. In general, it was determined that the valgus orientation was optimal throughout the gait cycle, consistently exhibiting a stress distribution more similar to that of the intact femur. Minimal levels of anterior/posterior and inferior positioning were seen to be beneficial in achieving more physiological stresses in specific regions of interest within the proximal femur, while the anteverted orientation was only beneficial in loading under flexion. Overall, orthopaedic surgeons should aim to Implant straight short stem Hip Implants in valgus up to 10°, with an otherwise neutral position and version, unless some degree of deviation would be beneficial for a patient-specific reason. This work has implications for the best surgical placement of straight short stem Hip Implants to yield maximal biomechanical stability.
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investigating stress shielding spanned by biomimetic polymer composite vs metallic Hip stem a computational study using mechano biochemical model
Journal of The Mechanical Behavior of Biomedical Materials, 2015Co-Authors: Pouria Tavakkoli Avval, Saeid Samiezadeh, Vaclav Klika, Habiba BougheraraAbstract:Abstract Periprosthetic bone loss in response to total Hip arthroplasty is a serious complication compromising patient’s life quality as it may cause the premature failure of the Implant. Stress shielding as a result of an uneven load sharing between the Hip Implant and the bone is a key factor leading to bone density decrease. A number of composite Hip Implants have been designed so far to improve load sharing characteristics. However, they have rarely been investigated from the bone remodeling point of view to predict a long-term response. This is the first study that employed a mechano-biochemical model, which considers the coupling effect between mechanical loading and bone biochemistry, to investigate bone remodeling after composite Hip Implantation. In this study, periprosthetic bone remodeling in the presence of Carbon fiber polyamide 12 (CF/PA12), CoCrMo and Ti alloy Implants was predicted and compared. Our findings revealed that the most significant periprosthetic bone loss in response to metallic Implants occurs in Gruen zone 7 (−43% with CoCrMo; −35% with Ti) and 6 (−40% with CoCrMo; −29% with Ti), while zone 4 has the lowest bone density decrease with all three Implants (−9%). Also, the results showed that in terms of bone remodeling, the composite Hip Implant is more advantageous over the metallic ones as it provides a more uniform density change across the bone and induces less stress shielding which consequently results in a lower post-operative bone loss (−9% with CF/PA12 Implant compared to −27% and −21% with CoCrMo and Ti alloy Implants, respectively).
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the biomechanics of plate repair of periprosthetic femur fractures near the tip of a total Hip Implant the effect of cable screw position
Proceedings of the Institution of Mechanical Engineers. Part H Journal of engineering in medicine, 2011Co-Authors: A Dubov, S Y R Kim, Suraj Shah, Emil H Schemitsch, Radovan Zdero, Habiba BougheraraAbstract:Optimal surgical positioning of cable-screw pairs in repairing periprosthetic femur fractures near the tip of a total Hip Implant still remains unclear. No studies in the literature to date have developed a fully three-dimensional finite element (FE) model that has been validated experimentally to assess these injury patterns. The aim of the present study was to evaluate the biomechanical performance of three different Implant-bone constructs for the fixation of periprosthetic femoral shaft fractures following total Hip arthroplasty. Experimentally, three bone-plate repair configurations were applied to the periprosthetic synthetic femur fractured with a 5 mm gap near the tip of a total Hip Implant. Constructs A, B, and C, respectively, had successively larger distances between the most proximal and the most distal cable-screw pairs used to affix the plate. Specimens were oriented in 15 degrees adduction, subjected to 1000 N of axial force to simulate the single-legged stance phase of walking, and instrumented with strain gauges. Computationally, a linearly elastic and isotropic three-dimensional FE model was developed to mimic the experimental setup. Results showed excellent agreement between experimental versus FE analysis strains, yielding a Pearson linearity coefficient, R2, of 0.90 and a slope for the line of best data fit of 0.96. FE axial stiffnesses were 601 N/mm (Construct A), 849 N/mm (Construct B), and 1359 N/mm (Construct C). FE surface stress maps for cortical bone showed maximum von Mises values of 74 MPa (Construct A), 102 MPa (Construct B), and 57 MPa (Construct C). FE stress maps for the metallic components showed minimum von Mises values for Construct C, namely screw (716MPa), cable (445MPa), plate (548MPa), and Hip Implant (154MPa). In the case of good bone stock, as modelled by the present synthetic femur model, optimal fixation can be achieved with Construct C.
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the biomechanics of plate fixation of periprosthetic femoral fractures near the tip of a total Hip Implant cables screws or both
Proceedings of the Institution of Mechanical Engineers. Part H Journal of engineering in medicine, 2011Co-Authors: Suraj Shah, Habiba Bougherara, A Dubov, S Y R Kim, Emil H Schemitsch, Radovan ZderoAbstract:Femoral shaft fractures after total Hip arthroplasty (THA) remain a serious problem, since there is no optimal surgical repair method. Virtually all studies that examined surgical repair methods have done so clinically or experimentally. The present study assessed injury patterns computationally by developing three-dimensional (3D) finite element (FE) models that were validated experimentally. The investigation evaluated three different constructs for the fixation of Vancouver B1 periprosthetic femoral shaft fractures following THA. Experimentally, three bone plate repair methods were applied to a synthetic femur with a 5 mm fracture gap near the tip of a total Hip Implant. Repair methods were identical distal to the fracture gap, but used cables only (construct A), screws only (construct B), or cables plus screws (construct C) proximal to the fracture gap. Specimens were oriented in 15 degrees adduction to simulate the single-legged stance phase of walking, subjected to 1000 N of axial force, and instrumented with strain gauges. Computationally, a linearly elastic and isotropic 3D FE model was developed to mimic experiments. Results showed excellent agreement between experimental and FE strains, yielding a Pearson linearity coefficient, R2, of 0.92 and a slope for the line of best data fit of 1.06. FE-computed axial stiffnesses were 768 N/mm (construct A), 1023 N/mm (construct B), and 1102 N/mm (construct C). FE surfaces stress maps for cortical bone showed Von Mises stresses, excluding peaks, of 0-8 MPa (construct A), 0-15 MPa (construct B), and 0-20 MPa (construct C). Cables absorbed the majority of load, followed by the plates and then the screws. Construct A yielded peak stress at one of the empty holes in the plate. Constructs B and C had similar bone stress patterns, and can achieve optimal fixation.
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A biomechanical assessment of modular and monoblock revision Hip Implants using FE analysis and strain gage measurements
Journal of Orthopaedic Surgery and Research, 2010Co-Authors: Habiba Bougherara, Suraj Shah, Rad Zdero, Milan Miric, Marcello Papini, Paul Zalzal, Emil H SchemitschAbstract:The bone loss associated with revision surgery or pathology has been the impetus for developing modular revision total Hip prostheses. Few studies have assessed these modular Implants quantitatively from a mechanical standpoint. Three-dimensional finite element (FE) models were developed to mimic a Hip Implant alone (Construct A) and a Hip Implant-femur configuration (Construct B). Bonded contact was assumed for all interfaces to simulate long-term bony ongrowth and stability. The Hip Implants modeled were a Modular stem having two interlocking parts (Zimmer Modular Revision Hip System, Zimmer, Warsaw, IN, USA) and a Monoblock stem made from a single piece of material (Stryker Restoration HA Hip System, Stryker, Mahwah, NJ, USA). Axial loads of 700 and 2000 N were applied to Construct A and 2000 N to Construct B models. Stiffness, strain, and stress were computed. Mechanical tests using axial loads were used for Construct A to validate the FE model. Strain gages were placed along the medial and lateral side of the Hip Implants at 8 locations to measure axial strain distribution. There was approximately a 3% average difference between FE and experimental strains for Construct A at all locations for the Modular Implant and in the proximal region for the Monoblock Implant. FE results for Construct B showed that both Implants carried the majority (Modular, 76%; Monoblock, 66%) of the 2000 N load relative to the femur. FE analysis and experiments demonstrated that the Modular Implant was 3 to 4.5 times mechanically stiffer than the Monoblock due primarily to geometric differences. This study provides mechanical characteristics of revision Hip Implants at sub-clinical axial loads as an initial predictor of potential failure.
Dmitry Royhman - One of the best experts on this subject based on the ideXlab platform.
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wear mapping based prediction methods for improved fretting corrosion performance of Hip Implant modular interfaces
Orthopaedic Proceedings, 2018Co-Authors: Dmitry Royhman, Nadim J Hallab, Joshua J Jacobs, Mathew T. MathewAbstract:Modern Hip Implants feature a modular design, whereby the individual components of the Implant are assembled during the surgery. Increased reported failure rates associated with the utilization of modular junctions have raised many clinical concerns about the increased release of metal ions/debris leading to adverse local tissue reactions. Implant materials are subject to a myriad of mechanical motion and forces, and varying electrochemical conditions and pH changes from the surrounding environment. To date, no studies have attempted to model the collected data in order to predict the performance of the materials so that precautions can be taken before the problem reaches the critical stage. This study reports the effects of pH variation, displacement variation, and load variation on the mechanical and corrosion behavior of the Hip Implant modular junction system, tested with a custom-built fretting-corrosion apparatus. The main objective of this study is to combine the complete data set of the in-vitro e...
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In vitro simulation of fretting-corrosion in Hip Implant modular junctions: The influence of pH
Medical Engineering and Physics, 2018Co-Authors: Dmitry Royhman, Megha Patel, Nadim J Hallab, Joshua J Jacobs, Markus A Wimmer, Mathew T. MathewAbstract:Background: The fretting-corrosion behavior of mixed metal contacts is affected by various mechanical and electrochemical parameters. Crevice conditions at the junction and patient-specific pathologies can affect the pH of the prosthetic environment. The main objective of this study is to understand the effect of pH variation at the stem/head junction of the Hip Implant under fretting corrosion exposure. We hypothesized that pH will have a significant influence on the fretting-corrosion behavior Hip Implant modular junctions. Materials and methods: A custom-made setup was used to evaluate the fretting corrosion behavior of Hip Implant modular junctions. A Newborn calf serum solution (30 g/L protein content) was used to simulate the synovial fluid environment. A sinusoidal fretting motion, with a displacement amplitude of +50 µm, was applied to the Ti alloy rod. The effects of pathology driven, periprosthetic pH variation were simulated at four different pH levels (3.0, 4.5, 6.0 and 7.6). Electrochemical and mechanical properties were evaluated before, during, and after the applied fretting motion. Results: The impedance of the system was increased in response to the fretting motion. The hysteresis tangential load/displacement behavior was not affected by pH level. The worn surfaces of CoCrMo pins exhibited the presence of tribolayer or organic deposits, in the pH 4.5 group, which may explain the lower drop in potential and mass loss observed in that group. Mechanically dominated wear mechanisms, namely, adhesive wear was shown in the pH 7.6 group, which may account for a higher potential drop and metal content loss. Conclusions: This study suggests that the fretting-corrosion mechanisms in Hip Implant are affected by the pH levels of the surrounding environment and patient-specific factors.
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wear mapping based prediction methods for improved fretting corrosion performance of Hip Implant modular interfaces
Journal of Bone and Joint Surgery-british Volume, 2017Co-Authors: Dmitry Royhman, Nadim J Hallab, Joshua J Jacobs, Mathew T. MathewAbstract:Modern Hip Implants feature a modular design, whereby the individual components of the Implant are assembled during the surgery. Increased reported failure rates associated with the utilization of modular junctions have raised many clinical concerns about the increased release of metal ions/debris leading to adverse local tissue reactions. Implant materials are subject to a myriad of mechanical motion and forces, and varying electrochemical conditions and pH changes from the surrounding environment. To date, no studies have attempted to model the collected data in order to predict the performance of the materials so that precautions can be taken before the problem reaches the critical stage. This study reports the effects of pH variation, displacement variation, and load variation on the mechanical and corrosion behavior of the Hip Implant modular junction system, tested with a custom-built fretting-corrosion apparatus. The main objective of this study is to combine the complete data set of the in-vitro experiments to create fretting-corrosion wear maps that can predict the dangerous domains of the Hip Implant modular system. For each test, the flat portions of two CoCrMo pins were loaded perpendicularly against a Ti6Al4V Rod (Ti alloy) in a Flat-on-flat configuration in a simulated synovial fluid in order to simulate the modular Hip Implant system. A schematic diagram of contact conditions is presented in Figure 1. A sinusoidal displacement was applied onto the rod, which articulated against the CoCrMo alloy pins, at a frequency of 1Hz. The experiential data from the fretting-corrosion tests has been used to create fretting-corrosion maps. The variables incorporated into the maps include: total mass loss, electrochemical destabilization, pH variation, load variation, displacement variation, and visual examination of the wear features of the contact zone. Total mass loss has been estimated via measurement of the simulator fluid by ICP-MS technique. Electrochemical destabilization was evaluated by a single parameter (V Drop ). The electrochemical destabilization of the tribosystem was evaluated by measuring the drop in potential, V Drop (V vs. SCE), resultant from the initiation of the fretting phase. The V Drop refers to the initial cathodic drop in potential in response to the initial onset of fretting motion. The data from the in vitro fretting-corrosion experiments has been combined to create four fretting-corrosion maps (Figures 2A–3D). Partial slip wear features and mechanical behavior was observed at 25µm displacement. 25–150µm displacement amplitudes showed gross slip behavior. Anything larger than 150µm displayed wear features that were indistinguishable from sliding wear. In general, total mass loss and V Drop increased with increasing displacement. Samples that were tested at pH 6.0 or higher showed signs of material transfer and higher V Drop . Finally, there was a general decrease in V Drop with increased applied load and pH. In general, the wears maps were able to offer some predictive validity, however, there were some discrepancies between visual observations and the observed damage parameters. It is possible that other parameters could offer better correlation. Future studies will be conducted to measure other parameters. For figures/tables, please contact authors directly.
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Fretting-corrosion behavior in Hip Implant modular junctions: The influence of friction energy and pH variation
Journal of the Mechanical Behavior of Biomedical Materials, 2016Co-Authors: Dmitry Royhman, Maria J. Runa, Megha Patel, Nadim J Hallab, Joshua J Jacobs, Markus A Wimmer, Mathew T. MathewAbstract:Background: Recently, there has been increasing concern in the orthopedic community over the use of Hip Implant modular devices due to an increasing number of reports of early failure, failure that has been attributed to fretting-corrosion at modular interfaces. Much is still unknown about the electrochemical and mechanical degradation mechanisms associated with the use of such devices. Purpose: Accordingly, the purpose of our study was to develop a methodology for testing the fretting-corrosion behavior of modular junctions. Methods: A fretting-corrosion apparatus was used to simulate the fretting-corrosion conditions of a CoCrMo Hip Implant head on a Ti6Al4V Hip Implant stem. The device features two perpendicularly-loaded CoCrMo pins that articulated against a Ti6Al4V rod. A sinusoidal fretting motion was applied to the rod at various displacement amplitudes (25, 50, 100, 150 and 200 μm) at a constant load of 200 N. Bovine calf serum at two different pH levels (3.0 and 7.6) was used to simulate the fluid environment around the joint. Experiments were conducted in two modes of electrochemical control - free-potential and potentiostatic. Electrochemical impedance spectroscopy tests were done before and after the fretting motion to assess changes in corrosion kinetics. Results: In free potential mode, differences were seen in change in potential as a function of displacement amplitude. In general, VDrop (the drop in potential at the onset of fretting), VFretting, (the average potential during fretting), δVFretting (the change in potential from the onset of fretting to its termination) and VRecovery (the change in potential from the termination of fretting until stabilization) appeared linear at both pH levels, but showed drastic deviation from linearity at 100 μm displacement amplitude. Subsequent EDS analysis revealed a large number of Ti deposits on the CoCrMo pin surfaces. Potentiostatic tests at both pH levels generally showed increasing current with increasing displacement amplitude. Electrochemical impedance spectroscopy measurements from free potential and potentiostatic tests indicated increased levels of resistance of the system after induction of the fretting motion. In free potential tests, the largest increase in impedance was found for the 100 μm group. Conclusions: We conclude that the 100 μm group exhibits deviations from linearity for several parameters, and this was most likely due to adhesive wear between Ti6Al4V and CoCrMo surfaces. Overall, the degradation of the system was dominated by wear at all pH levels, and displacement amplitudes.
Bart Raeymaekers - One of the best experts on this subject based on the ideXlab platform.
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Surface Texturing of Prosthetic Hip Implant Bearing Surfaces: A Review
Journal of Tribology, 2020Co-Authors: Quentin Allen, Bart RaeymaekersAbstract:Abstract More than 300,000 total Hip replacement surgeries are performed in the United States each year to treat degenerative joint diseases that cause pain and disability. The statistical survivorsHip of these Implants declines significantly after 15–25 years of use because wear debris causes inflammation, osteolysis, and mechanical instability of the Implant. This limited longevity has unacceptable consequences, such as revision surgery to replace a worn Implant, or surgery postponement, which leaves the patient in pain. Innovations such as highly cross-linked polyethylene and new materials and coatings for the femoral head have reduced wear significantly, but longevity remains an imminent problem. Another method to reduce wear is to add a patterned microtexture composed of micro-sized texture features to the smooth bearing surfaces. We critically review the literature on textured orthopedic biomaterial surfaces in the context of prosthetic Hip Implants. We discuss the different functions of texture features by highlighting experimental and simulated results documented by research groups active in this area. We also discuss and compare different manufacturing techniques to create texture features on orthopedic biomaterial surfaces and emphasize the key difficulties that must be overcome to produce textured prosthetic Hip Implants.
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predicting the polyethylene wear rate in pin on disc experiments in the context of prosthetic Hip Implants deriving a data driven model using machine learning methods
Tribology International, 2019Co-Authors: Alireza Borjali, Kenneth L Monson, Bart RaeymaekersAbstract:Abstract Pin-on-disc (PoD) experiments are widely used to quantify and rank wear of different material couples for prosthetic Hip Implant bearings. However, polyethylene wear results obtained from different PoD experiments are sometimes difficult to compare, which potentially leaves information inaccessible. We use machine learning methods to implement several data-driven models, and subsequently validate them by quantifying the prediction error with respect to published experimental data. A data-driven model can supplement results from PoD wear experiments, and enables predicting polyethylene wear of new PoD experiments based on its operating parameters. It also reveals the relative contribution of individual PoD operating parameters to the resulting polyethylene wear, thus informing design of experiments, and potentially reducing the need for time consuming PoD wear measurements.
Lazar Mathew - One of the best experts on this subject based on the ideXlab platform.
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Novel approach for designing a low weight Hip Implant used in total Hip arthroplasty adopting skeletal design techniques.
Artificial Organs, 2011Co-Authors: Sudesh Sivarasu, Pearline Beulah, Lazar MathewAbstract:Aseptic loosening is the major cause of failure of Hip Implants after total Hip arthroplasty. Stress shielding of the femur is known to be the principal factor involved in the aseptic loosening of Hip Implants. Solid stems are found to have a greater rigidity; therefore, they transfer less load proximally, which results in greater stress shielding of the proximal femur. A stem of low stiffness alone would not suffice in achieving a reduced or optimal stress shielding. The femoral stem of the light weight Hip Implant has a skeletal design with a hexagonal base and neck cross-section. This novel design would ameliorate the Implant fixation, aid in optimal rigidity, enhance the medullary revascularization, and offer better mobility to the patient.
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OPTIMIZATION OF SKELETAL Hip Implant CROSS-SECTIONS
2010Co-Authors: Sudesh Sivarasu, Pearline Beulah, Lazar MathewAbstract:Aseptic loosening is the most important cause of failure in total Hip replacement (THR), associated with pain and restriction in the range of the joint motion. Solid stems are found to have a greater rigidity, therefore, transfer fewer loads proximally, which results in high proximal stress shielding of the proximal femur. A stem of low stiffness alone would not suffice in achieving a reduced or optimal stress shielding. A skeletal Hip Implant with varying cross-sections was designed and analysed. The skeletal Hip Implant with a hexagonal cross section had a better load bearing capacity. This novel design would ameliorate the Implant fixation, minimize stress shielding, maintain appropriate strength, rigidity, enhance the longevity of the Implant and relieves patients from discomfort.
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Design Optimization of Skeletal Hip Implant Cross- Sections Using Finite-Element Analysis
Journal of Long-Term Effects of Medical Implants, 2009Co-Authors: Pearline Beulah, Sudesh Sivarasu, Lazar MathewAbstract:The major causes for revision surgery after total Hip arthroplasty are aseptic loosening, dislocation, wear, design factors, stress shielding on the bone, and mechanical and biological factors. A material with toughness and high wear properties is essential for a good Hip Implant because these Implants fail due to design. Stress shielding is found to be the major cause for the failure of Hip Implants, and can lead to the Implant needing to be replaced or revised, which is painful for the patient and costly for the health care industry. The Hip stem designs developed by various manufacturers are solid stems with indentations; stems with collars; collarless, tapered stems; and teardrop-shaped, polished stems without indentations. They are found to have a greater rigidity, and therefore they transfer less load proximally, which results in high proximal stress shielding of the proximal femur. A stem of low stiffness alone would not suffice in achieving a reduced or optimal stress shielding. The existing design proposals to minimize the effect of stress shielding are focused on the use of lightweight materials, composite materials, circular and longitudinal hole patterns, and different hollow-bore depths. A skeletal Hip Implant with varying cross-sections was designed and finite-element analysis was performed. The skeletal Hip Implant with a hexagonal cross-section was optimized based on the mass of the Implant and the load-bearing capacity. This lightweight, novel design ameliorates Implant fixation, minimizes stress shielding, enhances the longevity of the Implant, and offers better mobility to the patient.