A novel approach to address the clinical issue of cell response to wear and corrosion debris from metal orthopedic implants consists of combining cell culturing with wear and corrosion debris ...generation. A biotribometer equipped with a three-electrode electrochemical chamber operates inside a CO
incubator. Cells are cultured at the bottom of the chamber. A ceramic ball (hip implant head) is pressed against a metal disc under a constant load, and set in reciprocating rotation. An anodic electrochemical potential can be applied to a metal disc for accelerated corrosion conditions, or the free potential may be monitored.Measurements of gravimetric and volumetric material loss of the metal disc postwear provide quantitative information that can be put in relation to biological assays (e.g., cell viability and secretion of proinflammatory cytokines). This approach allows for the comparison of candidate metals potentially undergoing tribocorrosion in clinical use. The approach allows to identify the effect of any metastable debris, likely active in vivo.
Highlights • Various adjustments of cadence and stride length were studied. • Increasing cadence to walk faster did not increase joint moments. • Increasing stride length yield significant increases ...in joint moments. • Manipulating stride length-cadence relationship could be a step toward gait retraining.
This article was updated on May 13, 2011, because of previous editorial errors.On page 76, the affiliation that had previously read “Departments of Mechanical Engineering Surgery, and Biochemistry, ...Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada” now reads “Departments of Mechanical Engineering, Surgery & Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada.”On page 79, the line that had previously read “The percentage of these needle-shaped particles was the highest with hip replacements implanted for more than twenty years,” now reads “The percentage of these needle-shaped particles was the highest with hip replacements implanted for more than twenty years (average and standard deviation of 28% ± 9%).”On page 80, the previous incorrect version of Figure 3 has been replaced with the correct version.On page 82, the last line in reference 15, which had previously read “Paper no. 214,” now reads “Paper no. 365.”An erratum has been publishedJ Bone Joint Surg Am 2011;93(12):1158.
BACKGROUND:Despite the renewed interest in metal-on-metal implants in the past two decades, the underlying wear mechanisms and biological effects are still not fully understood.
METHODS:This paper first reviews the tribology of metal-on-metal bearings, bringing new insights into the interaction of wear and corrosion, and putting the characteristics and the potential origin of wear particles in perspective with the proposed wear mechanisms. It then summarizes the current knowledge on the biological effects of particles and metal ions in relation to these wear mechanisms.
RESULTS:Tribochemical reactions play an important role in the wear of metal-on-metal joints. The generated tribomaterial, which progressively forms by mechanical mixing of the uppermost nanocrystalline zone of the metal surface with proteins from the synovial fluid, governs the wear rate and influences the corrosive behavior of the bearing. Nanometer-sized wear particles may initially originate from the passivation layer covering the implant surface and then detach from this tribolayer. The inflammatory response observed surrounding metal-on-metal implants appears to be lower than that around metal-on-polyethylene implants. However, metallic byproducts, which can complex with proteins, may lead to a T lymphocyte-mediated hypersensitivity response.
CONCLUSIONS:The tribolayer appears to have beneficial effects on the wear rate. Much information has been gained on wear particle characteristics, but the exact mechanisms of particle detachment remain to be further elucidated. Excessive wear along with a hypersensitivity response may be at the origin of the early adverse tissue reactions that have been recently reported in some patients with metal-on-metal implants.
CLINICAL RELEVANCE:Future development of new methods to improve the tribolayer retention and optimize the tribocorrosive properties of the implant may minimize the clinical impact of implant wear and immune responses.
It remains unknown if hip joint forces during squat tasks are altered in people with femoroacetabular impingement syndrome (FAIS). The aim of this study is to compare hip joint forces between people ...with FAIS and healthy controls during double leg squat and single leg squat tasks and within limbs during a single leg squat task in people with FAIS. Kinematic and kinetic data were collected in eight people with FAIS and eight healthy matched controls using 3D motion capture and force plates. AnyBody Modeling System was used to perform musculoskeletal simulations to estimate hip joint angles, forces, and moments for all participants. Estimates were postprocessed with AnyPyTools and converted into normalized time series to be compared using a 1D statistical nonparametric mapping (SnPM) approach. SnPM with an independent samples t‐test model was used to compare people with FAIS to controls, while a paired samples model was used to compare involved to uninvolved limb in people with FAIS. Patients demonstrated lower proximodistal force compared to controls (p < 0.01) and compared to the uninvolved side (p = 0.01) for single leg squat. The smaller joint contact forces in people with FAIS compared to controls could represent a strategy of reduced muscle forces to avoid pain and symptoms during this high demand task. These findings when combined with imaging data could help assess the severity of FAIS on hip related function during higher demand tasks.
CoCrMo alloys are well‐established biomaterials used for orthopedic joint replacement implants. However, such alloys have been associated with clinical problems related to wear and corrosion. A new ...generation of austenitic high‐nitrogen steels (AHNSs) has been developed for biomedical applications. Here, we have addressed influences of hyaluronic acid, combined with inflammatory (oxidizing) conditions, on tribocorrosion of the high‐nitrogen FeCrMnMoN0.9 steel (DIN/EN X13CrMnMoN18‐14‐3, 1.4452), and of the low carbon CoCrMo0.03 alloy (ISO 5832‐12). We aimed to elucidate critical and clinically relevant conditions affecting the implant's performance in certain orthopedic applications. Tribocorrosion tests were conducted in triplicate, with discs under reciprocating sliding wear against a ceramic ball. Different lubricants were prepared from standardized bovine serum solution (ISO 14242‐1), with variable additions of hyaluronic acid (HA) and hydrogen peroxide (H2O2). Test conditions were: 37°C, 86,400 cycles, 37 N load (20–40 MPa after run‐in phase). Volumetric wear was quantified; surfaces were evaluated by electrochemical parameters and microscopy/spectroscopy analyses (SEM/EDS). Factorial analysis of variance tests was conducted to examine the effects of HA, H2O2, and test material on wear‐ and corrosion‐related dependent variables. Tribocorrosion performances of CoCrMo0.03 and FeCrMnMoN0.9 were comparable in fluids without H2O2. With higher H2O2 concentrations, tribocorrosion increased for CoCrMo0.03, while this was not the case for FeCrMnMoN0.9. HA significantly enhanced wear of CoCrMo0.03 in the absence of H2O2, while it mitigated the tribocorrosive action of 3 mM H2O2; HA had no impact on FeCrMnMoN0.9. These results indicate a favorable performance of FeCrMnMoN0.9 compared to CoCrMo0.03, and encourage further research on AHNS for certain orthopedic applications.
Austenitic high nitrogen steels (AHNS) are candidate materials to replace CoCrMo‐alloys for orthopedic implant components, with matching the mechanical properties. This is the first study comparing tribocorrosion between AHNS and CoCrMo with clinically relevant test parameters and fluids.
Background
Although numerous in vitro studies report on the tribological performance of and, separately, on the corrosion properties of cobalt-based alloys in metal-on-metal (MoM) bearings, the few ...studies that take into account the synergistic interaction of wear and corrosion (tribocorrosion) have used canonical tribo-test methods. We therefore developed synergistic study using a test method that more closely simulates hip bearing conditions.
Questions/purposes
(1) Is the total material loss during tribocorrosion larger than the sum of its components generated during isolated mechanical wear and isolated corrosion? (2) How is the tribocorrosive process affected by the presence of protein?
Methods
High carbon CoCrMo alloy discs (18) were subjected to corrosion and tribocorrosion tests under potentiostatic conditions in an apparatus simulating hip contact conditions. The input variables were the applied potential and the protein content of the electrolyte (NaCl solution versus bovine serum, 30 g/L protein). The output variables were mass loss resulting from wear in the absence of corrosion, mass loss resulting from corrosion in the absence of wear, and the total mass loss under tribocorrosion, from which the additional mass loss resulting from the combined action of wear and corrosion, or synergism, was determined in the presence and absence of protein.
Results
The degradation mechanisms were sensitive to the interaction of wear and corrosion. The synergistic component (64 μg) in the presence of protein amounted to 34% of total material loss (187 μg). The presence of protein led to a 23% decrease in the total mass loss and to a considerable reduction in the mean current (4 μA to 0.05 μA) under tribocorrosion.
Conclusions
Synergistic effects during tribocorrosion may account for a considerable portion of MoM degradation and are affected by proteins.
Clinical Relevance
The in vivo performance of some large-diameter MoM joints is unsatisfactory. The synergistic component resulting from tribocorrosion may have been missed in conventional preclinical wear tests.
•Subjects reduced knee adduction moment after gait retraining following feedback.•Gait modification cued by pressure-based auditory feedback reduced both KAM peaks.•Equipment allowed unsupervised ...gait retraining.•The wireless shoe insole is ready to be implemented in studies with OA subjects.
The knee adduction moment (KAM) is a surrogate measure of mediolateral distribution of loads across the knee joint and is correlated with progression and severity of knee osteoarthritis (OA). Existing biomechanical approaches for unloading the arthritic medial knee compartment vary in their effectiveness in reducing KAM. This study employed a completely wireless, pressure-detecting shoe insole capable of generating auditory feedback via a smartphone. Research question: To investigate whether auditory cues from a smartphone can prompt subjects to adjust their gait pattern and reduce KAM. Methods: Nineteen healthy subjects underwent gait training inside the lab (Phase 1) and received auditory cues during mid- and terminal stance to medialize their foot COP (center-of-pressure). This initial training period was continued unsupervised while walking around campus (Phase 2).
After Phase 1, subjects reduced their KAM by 20.6% (p = 0. 001), a finding similar to a previous study that used a wired, lab-based insole system. After further unsupervised training outside the lab during Phase 2, subjects were able to execute the newly learned gait pattern without auditory feedback still showing a KAM reduction of 17.2% (p < 0.001). Although, speed at Phase 2 was lower than at baseline (p = 0.013), this reduction had little effect on KAM (r = 0.297, p = 0.216). In addition, the adduction angular impulse was reduced (p = 0.001), despite the slower speed.
Together, these results suggest that the wireless insole is a promising tool for gait retraining to lower the KAM and will be implemented in a home-based clinical trial of gait retraining for subjects with knee OA.
Nickel‐free, high‐nitrogen austenitic steels (AHNS) have been introduced for biomedical applications, with encouraging results in terms of mechanical and corrosion properties. Here, we tested the ...corrosion resistance of a nickel‐free high nitrogen steel (FeCrMnMoN0.9) in bovine serum solutions containing 0 or 3 g/L hyaluronic acid (HA), and 0, 3, or 30 mM hydrogen peroxide (H2O2) simulating no, moderate, or strong inflammatory conditions, respectively. Nondestructive electrochemical measurements (open circuit potential OCP, linear polarization resistance “RP”, and electrochemical impedance spectroscopy) were run in triplicate over 10 hr. The presence of HA had no significant effect either on the stabilized OCP values, or on the corrosion resistance of FeCrMnMoN0.9. Increasing H2O2 concentrations shifted the OCP to more electropositive values; the corrosion resistance decreased only at a 30 mM H2O2. Final RP values at 0, 3, and 30 mM H2O2 resulted in 1598 ± 276, 1746 ± 308, and 439 ± 47 kΩ cm2, respectively. These values were 4–14 times higher, than the RP values measured on LC‐CoCrMo in our previous study, conducted under identical conditions. While these findings are encouraging, future studies need to focus on tribocorrosive properties of the AHNS to evaluate its applicability in joint replacement.
Abstract Hip osteoarthritis (OA) has been shown to affect gait patterns of lower extremities. However, until now, no specific identifying gait characteristics for the various disease stages of hip OA ...have emerged. The present study addresses the following questions: (1) Does a vector-based principal component analysis (PCA) discriminate between various disease stages? And, is this analysis more robust than using discrete gait variables? (2) Does the elimination of differences in walking speed affect the discriminatory robustness of a vector-based PCA? De-identified data sets of forty-five unilateral hip OA patients with varying disease stages and twenty-three age-matched, healthy control subjects were obtained from an available repository. PCA was performed on trial matrices consisting of all external joint moments and sagittal joint angles of one full gait cycle. Group differences in sagittal angles, external moments and the linear combination of PC vectors were investigated using spatial parameter mapping (SPM), a statistical vector field test. Several individual gait variables (i.e. joint moments or angles) demonstrated differences between healthy and moderately and/or severely affected subjects. Only the hip adduction moment could discriminate between the healthy and the early-stage OA group. There was no variable that could distinguish between all OA disease stages. In contrast, the linear combination of PC vectors demonstrated significant group differences between all stages of osteoarthritis; furthermore, these group differences stayed significant when matched speeds were input to the model.
This contribution is aimed at the detailed understanding of lubrication mechanisms within total knee replacement. While Part I is focused on the experimental investigation, Part II deals with the ...development of a predictive numerical model. Here, a knee simulator was used for direct optical observation of the contacts between a metal femoral and a transparent polymer components. Transient dynamic conditions were applied. Mimicked synovial fluids with fluorescently labelled constituents were used as the test lubricants. The results showed that γ-globulin forms thin boundary lubricating film, being reinforced by the interaction of phospholipids and hyaluronic acid. Further development of lubricating film is attributed to albumin layering. Based on the results, a novel lubrication model of the knee implant is proposed.
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•Employment of a knee simulator for exploration of lubrication mechanisms within TKA.•Comparison of experimental results with predictive numerical model.•Consideration of transient loading and kinematic conditions corresponding to ISO.•Fluorescent labeling enabling to determine the role of specific fluid constituents.•Novel lubrication model of TKA is proposed.
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