Material Loss at the Head Taper Junction of the Metal-on-Metal Pinnacle Total Hip Replacement

Introduction The ASR XL (DePuy) total hip replacement (THR) is a notable example of a modern metal-on-metal (MOM) implant design that has demonstrated unacceptable survival rates, leading to its recall by the manufacturer; national joint registries have reported revision rates at 7 years of 40% when paired with the Corail stem [1]. The ASR XL THR has a considerably greater risk of revision than the ASR resurfacing hip, which used the same bearing design. This suggests that material loss at the head-stem junction may be responsible for the greater percentage of THR failures observed in this design. The Pinnacle MOM-THR (DePuy) however used the same Corail stem as the ASR XL THR but demonstrated better clinical results, with revision rates of less than 10% at 7 years [1]. The ASR XL and MOM Pinnacle are two designs that have been widely used in hip replacement surgery. The reasons for the differences in the failure rates of the two designs are not fully understood. Comparing the mechanisms of failure of both hips will help surgeons understand whether patients with MOM Pinnacle hips will experience the same types of problems as with those seen with the ASR XL. The aims of this retrieval study were to investigate the significance of differences between the ASR XL and MOM Pinnacle in relation to: (1) pre-revision whole blood Co/Cr ratios, (2) visual evidence of taper corrosion, (3) volumetric material loss at the bearing surfaces and (4) volumetric material loss at the taper surfaces. Methods This study involved a series of failed MOM hips consisting of the ASR XL (n=30) and Pinnacle (n=30), all that had been used with a Corail stem. The bearing material in each design was cobalt-chromium and the Corail stem is of a cementless titanium 12/14 design. The ASR XL and Pinnacle had a median head diameter of 47mm (39-55) and 36mm (36-40) respectively, and a median time to revision of 38.5 months (12-74) and 55 months (14-86) respectively. Pre-revision whole blood metal ion levels were collected for each Table 1 summarises patient and implant data for the hips in this study. The female taper surfaces of all 60 heads were examined macroscopically and microscopically to assess the severity of corrosion. Each surface was graded with a score of between 1 (no corrosion) and 4 (severe corrosion) using a well-published scoring system, which has been shown to be statistically reliable. A Zeiss Prismo (Carl Zeiss Ltd, Rugby, UK) coordinate measuring machine (CMM) was used to determine the volume of material loss at the cup and head bearing surfaces. Up to 300,000 data points were collected using a 2mm ruby stylus that was translated along 400 polar scan lines on the surface. The raw data was used to map regions of material loss by comparing with the unworn geometry of the bearing. A Talyrond 365 (Hobson, Leicester, UK) roundness measuring machine was used to measure the volumetric material loss at each of the head taper surfaces. Published protocols were used to take a series of 180 vertical traces along the taper surface using a 5μm diamond stylus; worn and unworn regions were mapped and used to calculate material loss. Neither the volumetric measurement data nor corrosion scores were normally distributed. Therefore non-parametric tests were performed to assess the statistical significance of differences between the two designs in relation to the parameters under investigation in this study. Results Both the whole blood Co ion levels and the Co/Cr ratios, Figure 1, of the ASR XL hips were significantly greater than the Pinnacles (p<0.05). There was no significant difference between the whole blood Cr ion levels between the two designs (p=0.0542). 18 of the ASR XL hips presented evidence of edge wearing of the cup, compared with 14 Pinnacle hips; this difference was not significant (p=0.438). The length of the stem trunnion contact engagement length with the taper was approximated as being 10.5mm for both designs. The median time to revision of the ASR XL hips was significantly less than the Pinnacle hips (p<0.01). There was visual evidence of corrosion in 93% (n=28) and 90% (n=27) of head tapers for the ASR XLs and Pinnacles respectively. Moderate to severe corrosion was observed in 67% (n=20) of ASR XLs compared to 60% (n=18) of Pinnacles. There was however no statistically significant difference between the scores of the two groups (p=0.927). Figure 2 presents the distribution of material loss rates for the bearing and taper surfaces of the two designs in this study. The median total bearing surface (combined cup and head) rate of material loss for the ASR XL and Pinnacle hips was 4.45mm3/year (0.32-22.85) and 4.03mm3/year (0.87-62.12) respectively. There was no significant difference between the two groups (p=0.928). The median material loss rate at the taper surfaces of the ASR XL and Pinnacle hips was 0.62mm3/year (0-4.20) and 0.30mm3/year (0-3.12); this difference was not significant (p=0.198). Discussion The work of this study presents comparisons of retrieval findings between the ASR XL and Pinnacle MOM-THRs; these hip designs were two of the most commonly implanted in patients worldwide. The significantly greater whole blood Co/Cr ratios found in the ASR XL group compared to the Pinnacle group are of interest. It is speculated that a Co/Cr ratio of greater than 1 may be an indicator of corrosion of an implant whereby more Cr ions are retained on the surface, whilst comparatively more Co ions are released into the blood. In the current study we found wear rates at the bearing surfaces of both designs to be comparable, suggesting that the significantly greater Co/Cr ratios in the ASR XL hips must be due to greater corrosion at the taper junction than the Pinnacles. Although the ASR XL hips had been implanted for a significantly shorter period of time, our visual assessment of the corrosion of the taper junctions found that corrosion scores were comparable between the two designs; indeed, a marginally greater number of ASR XL tapers had evidence of moderate to severe corrosion. This finding, coupled with the elevated Co/Cr ratios suggests that the ASR XL design is more susceptible to corrosion at the taper junction than the Pinnacle hip. We found that the median rate of material loss at the ASR XL taper was over twice that of the Pinnacle taper. Whilst not statistically significant, this difference may be due to a greater risk of corrosion at this interface in the ASR XL design. The differences in material loss and corrosion that were observed at the taper junctions may be explained by considering the larger head sizes of the ASR XL hips in comparison to the Pinnacles. It has previously been shown that increasing head size is correlated with greater visual evidence of corrosion and that increased frictional torque along the taper junction due a larger head diameter can increase the risk of fretting-corrosion. It is suggested therefore that the combination of the larger head sizes of the ASR XLs coupled with the comparatively short, rough surface of the Corail trunnion results in a cumulative effect leading to greater corrosion at the taper junction. Significance The results of the study suggest that the combination of (1) increased frictional torque in the larger ASR XLs and (2) the rough Corail trunnion surface, results in greater corrosion at the taper junction in comparison to the Pinnacle hips; this helps to explain the higher risk of revision in this hip design

Implementation of a web-based resilience enhancement training for nurses : pilot randomized controlled trial

Background: Global workforce challenges faced by health care providers are linked to low levels of job satisfaction, recruitment, retention, and well-being, with detrimental impacts on patient care outcomes. Resilience-building programs can provide support for staff who endure highly stressful environments, enhance resilience, and support recruitment and retention, with web-based formats being key to increasing accessibility. Objective: We aimed to examine participants’ engagement with a newly developed Resilience Enhancement Online Training for Nurses (REsOluTioN), explore its acceptability, and compare levels of resilience and psychological well-being in nurses who completed REsOluTioN with those who did not. Methods: We carried out a pilot randomized trial (1:1), conducted at a single site (mental health and community trust in South England) between August 2021 and May 2022. Local research ethics approvals were obtained. Nurses were invited to participate and were randomly assigned to a waitlist group or REsOluTioN group. Training lasted for 4 weeks, consisting of prereading, web-based facilitated sessions, and mentorship support. We evaluated trial engagement, acceptability of training, and pre-post changes in resilience, measured by the Brief Resilience Scale, and psychological well-being, measured by the Warwick Edinburgh Mental Wellbeing Scale. Qualitative participant feedback was collected. Consolidated Standards of Reporting Trials 2010 extension guidelines for reporting pilot and feasibility trials were used. Results: Of 108 participants recruited, 93 completed the study. Participants’ mean age was 44 (SD 10.85) years. Most participants were female (n=95, 88.8%), White (n=95, 88.8%), and worked in community settings (n=91, 85.0%). Sixteen facilitated and 150 mentoring sessions took place. Most REsOluTioN program participants reported the sessions helped improve their resilience (n=24, 72.8%), self-confidence (n=24, 72.7%), ability to provide good patient care (n=25, 75.8%), relationships with colleagues (n=24, 72.7%), and communication skills (n=25, 75.8%). No statistically significant differences between training and control groups and time on well-being (F1,91=1.44, P=.23, partial η2=0.02) and resilience scores (F1,91=0.33, P=.57, partial η2=0.004) were revealed; however, there were positive trends toward improvement in both. Nurse participants engaged with the REsOluTioN program and found it acceptable. Most found web-based training and mentoring useful and enjoyed learning, reflection, networking, and participatory sessions. Conclusions: The REsOluTioN program was acceptable, engaging, perceived as useful, and nurses were keen for it to be implemented to optimize resilience, psychological health, communication, and workplace environments. The study has evidenced that it is acceptable to implement web-based resilience programs with similar design features within busy health care settings, indicating a need for similar programs to be carefully evaluated. Mentorship support may also be a key in optimizing resilience. Trial limitations include small sample size and reduced statistical power; a multicenter randomized controlled trial could test effectiveness of the training on a larger scale

Charactering taper junction wear helps understand the mechanism of failure of metal on metal hip replacements.

Introduction: Taper junction material loss is the result of corrosion and mechanical wear. The significance of the taper junction material loss is highlighted by studies that compared resurfacing and total hip replacements of the same type and size. High volumes of material loss are reported, especially from the head taper, but the pattern of wear is unknown. One report characterized the material loss pattern of five tapers (n=5) into axisymmetrical and asymmetrical, along the long axis of the taper. We noticed more than two patterns on our retrievals and we set out to characterize these types and relate them to clinical variables. Methods: We retrospectively analysed retrieved cobalt-chromium tapers (n=146) using a roundness measurement machine. We also performed a corrosion classification and collected clinical data (metal ion levels, time to revision, component sizes). A non-blinded author devised a four-group classification (table). Two blinded authors classified the material loss patterns derived from the roundness measurement machine. Results: The four groups of material loss patterns Low wear (n= 62), Open-end band (n=29), Stripped material loss (n=51) and Coup-Countercoup (n=4). Kappa was 0.78 (p<0.001) in the assessment of interobserver reliability. Kruskal-Wallis test revealed: - Significantly higher volumes of wear on the taper of Stripped material loss compared to Low wear (p<0.001) and Open-end band compared to Low wear (p<0.001) groups. - Significantly higher chromium ion blood levels in the open-end band compared to the Stripped material loss group. - Significantly higher Cobalt ion blood levels in the Stripped material loss compared to the Low wear group - Significantly higher Cobalt/Chromium ration in the Open-end band compared to the Low wear group One-way ANOVA analysis revealed: - Significant difference between in the head sizes between the groups (p=0.01). Post-hoc analysis located the difference between the Low wear (median=40, range=20) and Open-end band (median=49, range=20) groups (p<0.001). - Significantly higher time to revision in the Stripped material loss compared to the Low wear group (p=0.05), in the post-hoc analysis. - Significantly higher corrosion scores in the Stripped material loss compared to the Low wear group (p<0.001) and the Open-end band compared to the Low wear group (p<0.001). Discussion: The results suggests that corrosion becomes worse over time and that the material loss pattern evolves gradually from the Low wear to Open-end band and finally to Stripped. Further analysis is required to assess the factors that affect the Coup-countercoup group

Registry Data-Valuable Lessons But Beware the Confounders.

A mature national joint registry with widespread adoption and audit can successfully demonstrate trends and influence future orthopedic practice. Correlations can be identified; however, this should not be misinterpreted as causality. It is essential to consider confounding when analyzing observational datasets

Coherent phonons and the interplay between charge density wave and Mott phases in 1<i>T</i>-TaSe₂

1$T$-TaSe$_{2}$ is host to coexisting strongly-correlated phases including charge density waves (CDWs) and an unusual Mott transition at low temperature. Here, we investigate coherent phonon oscillations in 1$T$-TaSe$_{2}$ using a combination of time- and angle-resolved photoemission spectroscopy (TR-ARPES) and time-resolved reflectivity (TRR). Perturbation by a femtosecond laser pulse triggers a modulation of the valence band binding energy at the $\Gamma$-point, related to the Mott gap, that is consistent with the in-plane CDW amplitude mode frequency. By contrast, TRR measurements show a modulation of the differential reflectivity comprised of multiple frequencies belonging to the distorted CDW lattice modes. Comparison of the temperature dependence of coherent and spontaneous phonons across the CDW transition shows that the amplitude mode intensity is more easily suppressed during perturbation of the CDW state by the optical excitation compared to other modes. Our results clearly identify the relationship of the in-plane CDW amplitude mode with the Mott phase in 1$T$-TaSe$_{2}$ and highlight the importance of lattice degrees of freedom.Comment: 7 pages, 4 figures, supplemental materia

Characterisation of Wear Morphology at the Head Cup Bearing Interface in Retrieved Metal-on-Metal Hip Replacements

Abstract Background The changes in surface roughness occurring during the wear process at the bearing surface are of great importance in trying to understand the failure mechanism of large head metal-on-metal hip replacements. The aim of the study is to identify and characterise the areal surface parameter variation between the worn and unworn areas. Surface topography variations at the bearing surface have an effect on the lubrication regime [1]. In vitro tests of these components have suggested a “self-polishing” of the surface [2]. Traditionally Ra has been used as a descriptor of surface texture. Considering the high standard of manufacturing to which these components are produced, Ra is not sufficient to describe surface morphology which requires spatial information which can only be achieved through the use of areal parameters. Methods A total of 50 retrieved metal-on-metal hip replacements were assessed using white light scanning interferometry (Talysurf CCI, Ametek, UK) to determine the difference in the areal surface topography parameters between the worn and unworn regions of the bearing surface. The worn area was identified by use of a previously described method [3] to produce a wear map of the bearing surface, this allows the identification of the regions of interest. A series of six measurements were taken on each component (figure 1) comprising of: 2 measurements at the equator of the head representing the unworn region, one measurement at the pole and just off centre from the pole and the rest of the measurements were taken inside and at the boundary of the wear area. Each measurement covered an area of 1 mm2 therefore it is crucial that the location of the measurement be established as accurately as possible. Data was analysed to determine the most relevant parameters that could be used to describe and highlight the changes in surface roughness that occur during the wear process. Discussion The measurement methodology developed shows a clear correlation between the areal surface parameters and the wear regions. The parameters show that areas of wear can be identified when the correct suite of parameters are utilised. This information is invaluable in developing a more advanced model of change in the lubrication regimes due to morphological changes during wear

Correlation Between the Detailed Visual Inspection of Retrieved Metal-on-Metal Hips and Their Volumetric Wear

Abstract Introduction Metal-on-metal (MOM) total hip arthroplasty using large diameter femoral heads offer clinical advantages however the failure rates of these hips is unacceptably high. Retrieved hips have a wide range of wear rates of their bearing and taper surfaces and there is no agreement regarding the cause of failure. Detailed visual inspection is the first step in the forensic examination of failed hip components and may help explain the mechanisms of failure. The aim of this study was to determine if there was a correlation between the results of detailed inspections and the volumetric wear of the bearing and taper surfaces of retrieved hips. Method Detailed, non-destructive macroscopic and stereomicroscopic examinations of 89 retrieved MOM hip components were performed by a single experienced examiner using quantitative assessment to document the severity of 10 established damage features: Light scratches, Moderate scratches, Heavy scratches, Embedded particles, Discolouration, Haziness, Pitting, Visible wear zone, Corrosion, Fretting Each surface was considered in terms of zones comprising of quadrants (cup, head, and taper) and subquadrants (cup and head), Figure 1. Each zone was scored on a scale of 0 to 3 by determining the percentage of the surface area of the zone that exhibited the feature in question: a score of 0=0%, 175%. The sum of the scores of each zone was used for the assessment of each damage feature. The volume of wear at the surfaces of each hip was measured with a Zeiss Prismo coordinate measuring machine (cup and head) and a Talyrond 365 roundness measurement instrument (taper), using previously reported methods1, 2. Simple linear regression models were used to asses the univariable associations between the inspection scores and wear volumes. Multiple linear regression models were subsequently used to asses the simultaneous contribution of the inspection scores, found significant in univariable analyses, on the wear outcome variables. All statistical analysis was performed using Stata/IC version 12.1 (StataCorp, USA) and throughout a p value < 0.05 was considered statistically significant. Results Visible wear zone, moderate scratches, discolouration and haziness scores were all significantly positively correlated with cup (R2 = 70%, 23%, 72% and 33% respectively) and head (R2 = 73%, 34%, 67% and 47% respectively) wear volumes. Visible wear zone and discoloration scores were significant predictors in multivariable analysis (p < 0.01) for both surfaces, together explaining 77% and 79% of the variance in the cup and head wear volumes respectively. Corrosion and discoloration scores were significantly positively correlated with taper wear volume (R2 = 57% and 53% respectively) and there was a significant interaction between the two damage features (p = 0.01). Discussion This study demonstrates the importance of detailed visual inspections in retrieval analysis, suggesting that they may help in predicting the severity of bearing and taper surface wear. Future studies will involve assessments of the inter-observer errors of inspections and their relationship with many other variables such as implant design and patient factors

Taper wear contributes only a third of the total volumetric material loss in large head metal on metal hip replacement

Abstract It has been speculated that high wear at the head-stem taper may contribute to the high failure rates reported for stemmed large head metal-on-metal (LH-MOM) hips. In this study of 53 retrieved LH-MOM hip replacements, we sought to determine the relative contributions of the bearing and taper surfaces to the total wear volume. Prior to revision, we recorded the relevant clinical variables, including whole blood cobalt and chromium levels. Volumetric wear of the bearing surfaces was measured using a coordinate measuring machine and of the taper surfaces using a roundness measuring machine. The mean taper wear volume was lower than the combined bearing surface wear volume (p = 0.015). On average the taper contributed 32.9% of the total wear volume, and in only 28% cases was the taper wear volume greater than the bearing surface wear volume. Despite contributing less to the total material loss than the bearing surfaces, the head-stem taper junction remains an important source of implant-derived wear debris. Furthermore, material loss at the taper is likely to involve corrosion and it is possible that the material released may be more biologically active than that from the bearing surface

Personal non-commercial use only

ABSTRACT. Objective. To determine whether cytokine/chemokine profiles from synovial fluid and sera discriminate mild/moderate osteoarthritis (OA) from normal and severe OA cohorts. Methods. Multiplex technology was used to quantify expression levels for 42 cytokines in the synovial fluid of patients diagnosed with severe OA (n = 20) and mild/moderate OA (n = 12), as well as normal controls (n = 34). The same 42 cytokines were examined in serum samples of patients with severe OA (n = 26) and mild/moderate OA (n = 74) and normal individuals (n = 100)

OpenSAFELY: a platform for analysing electronic health records designed for reproducible research

Electronic health records (EHRs) and other administrative health data are increasingly used in research to generate evidence on the effectiveness, safety, and utilisation of medical products and services, and to inform public health guidance and policy. Reproducibility is a fundamental step for research credibility and promotes trust in evidence generated from EHRs. At present, ensuring research using EHRs is reproducible can be challenging for researchers. Research software platforms can provide technical solutions to enhance the reproducibility of research conducted using EHRs. In response to the COVID-19 pandemic, we developed the secure, transparent, analytic open-source software platform OpenSAFELY designed with reproducible research in mind. OpenSAFELY mitigates common barriers to reproducible research by: standardising key workflows around data preparation; removing barriers to code-sharing in secure analysis environments; enforcing public sharing of programming code and codelists; ensuring the same computational environment is used everywhere; integrating new and existing tools that encourage and enable the use of reproducible working practices; and providing an audit trail for all code that is run against the real data to increase transparency. This paper describes OpenSAFELY’s reproducibility-by-design approach in detail