ZrN-multilayer coating is clinically well established in total knee arthroplasty [1-3] and has demonstrated significant reduction in polyethylene wear and metal ion release [4,5]. The goal of our study was to analyze the biotribological behaviour of the ZrN-multilayer coating on a polished cobalt-chromium cemented hip stem. CoCr28Mo6 alloy hip stems with ZrN-multilayer coating (CoreHip®AS) were tested versus an un-coated version. In a worst-case-scenario the stems with ceramic heads have been tested in bovine serum in a severe cement interface debonding condition under a cyclic load of 3,875 N for 15 million cycles. After 1, 3, 5, 10 & 15 million cycles the surface texture was analysed by scanning-electron-microscopy (SEM) and energy-dispersive x-ray (EDX). Metal ion concentration of Co,Cr,Mo was measured by inductively coupled plasma mass spectroscopy (ICP-MS) after each test interval. Based on SEM/EDX analysis, it has been demonstrated that the ZrN-multilayer coating keeps his integrity over 15 million cycles of severe stem cemented interface debonding without any exposure of the CoCr28Mo6 substrate. The ZrN-multilayer coated polished cobalt-chromium cemented hip stem has shown a reduction of Co & Cr metal ion release by two orders of a magnitude, even under severe stem debonding and high interface micro-motion conditions. ZrN-multilayer coating on polished cobalt-chromium cemented hip stems might be a suitable option for further minimisation of Co & Cr metal ion release in total hip arthroplasty. Clinical evidence has to be proven during the next years

Systemic metal ion monitoring (Co;Cr) has proven to be a useful screening tool for implant performance to detect failure at an early stage in metal-on-metal hip arthroplasty. Several clinical studies have reported elevated metal ion levels after total knee arthroplasty (TKA), with fairly high levels associated with rotating hinge knees (RHK) and megaprostheses. 1. In a knee simulator study, Kretzer. 2. , demonstrated volumetric wear and corrosion of metallic surfaces. However, prospective in vivo data are scarce, resulting in a lack of knowledge of how levels evolve over time. The goal of this study was to measure serum Co and Cr levels in several types TKA patients prospectively, evaluate the evolution in time and investigate whether elevated levels could be used as an indicator for implant failure. The study was conducted at Ghent University hospital. 130 patients undergoing knee arthroplasty were included in the study, 35 patients were lost due to logistic problems. 95 patients with 124 knee prostheses had received either a TKA (primary or revision) (69 in 55 patients), a unicompartimental knee arthroplasty (7 UKA), a RHK (revision −7 in 6 patients) or a megaprosthesis (malignant bone tumours − 28 in 27 patients). The TKA, UKA and RHK groups were followed prospectively, with serum Co and Cr ions measured preoperatively, at 3,6 and 12 months postoperatively. In patients with a megaprosthesis, metal ions were measured at follow-up (cross-sectional study design). In primary knees, we did not observe an increase in serum metal ion levels at 3, 6 or 12 months. Two patients with a hip arthroplasty had elevated preTKA Co and Cr levels. There was no difference between unilateral and bilateral knee prostheses. In the revision group, elevated pre-revision levels were found in 2 failures for implant loosening. In both cases, ion levels decreased postoperatively. In revisions with a standard TKA, there was no significant increase in metal ions compared to primary knee arthroplasty. RHK were associated with a significant increase in Co levels even at short-term (3–12 months). The megaprosthesis group had the highest metal ion levels and showed a significant increase in Co and Cr with time in patients followed prospectively. With the current data, we could not demonstrate a correlation between metal ion levels, size of the implant or length of time in situ. In primary knee arthroplasty with a standard TKA or UKA, metal ion levels were not elevated till one year postoperatively. This suggests a different mechanism of metal ion release in comparison to metal-on-metal hip arthroplasties. In two cases of revision for implant loosening, pre-revision levels were elevated, possibly associated with component wear, and decreased after revision. With RHK, slightly elevated ion levels were found prospectively. Megaprostheses had significantly elevated Co and Cr levels, due to corrosion of large metallic surfaces and/or wear of components which were not perfectly aligned during difficult reconstruction after tumour resection. Further research is needed to assess the clinical relevance of metal ion levels in knee arthroplasty

A concern of metal on metal hip resurfacing arthroplasty is long term exposure to Cobalt (Co) and Chromium (CR) wear debris from the bearing. This study compares whole blood metal ion levels from patients drawn at one-year following Birmingham Hip Resurfacing (BHR) to levels taken at a minimum 10-year follow-up. A retrospective chart review was conducted to identify all patients who underwent a BHR for osteoarthritis with a minimum 10-year follow-up. Whole blood metal ion levels were drawn at final follow-up in June 2019. These results were compared to values from patients with one-year metal ion levels. Of the 211 patients who received a BHR, 71 patients (54 males and 17 females) had long term metal ion levels assessed (mean follow-up 12.7 +/− 1.4 years). The mean Co and Cr levels for patients with unilateral BHRs (43 males and 13 females) were 3.12 ± 6.31 ug/L and 2.62 ± 2.69 ug/L, respectively, and 2.78 ± 1.02 ug/L and 1.83 ± 0.65 ug/L for patients with bilateral BHRs (11 males and 4 females). Thirty-five patients (27 male and 8 female) had metal-ion levels tested at one-year postoperatively. The mean changes in Co and Cr levels were 2.29 ug/l (p = 0.0919) and 0.57 (p = 0.1612), respectively, at one year compared to long-term. These changes were not statistically significant. This study reveals that whole blood metal ion levels do not change significantly when comparing one-year and ten-year Co and Cr levels. These ion levels appear to reach a steady state at one year. Our results also suggest that regular metal-ion testing as per current Medicines and Healthcare products Regulatory Agency (MHRA) guidelines may be impractical for asymptomatic patients. Metal-ion levels, in and of themselves, may in fact possess little utility in determining the risk of failure and should be paired with radiographic and clinical findings to determine the need for revision

Introduction. Systemic metal ion monitoring (Co;Cr) has proven to be a useful screening tool for implant performance to detect failure at an early stage in metal-on-metal hip arthroplasty. Several clinical studies have reported elevated metal ion levels after total knee arthroplasty (TKA), with fairly high levels associated with rotating hinge knees (RHK) and megaprostheses. 1. In a knee simulator study, Kretzer. 2. , demonstrated volumetric wear and corrosion of metallic surfaces. However, prospective in vivo data are scarce, resulting in a lack of knowledge of how levels evolve over time. The goal of this study was to measure serum Co and Cr levels in several types TKA patients prospectively, evaluate the evolution in time and investigate whether elevated levels could be used as an indicator for implant failure. Patients and Methods. The study was conducted at Ghent University hospital. 130 patients undergoing knee arthroplasty were included in the study, 35 patients were lost due to logistic problems. 95 patients with 124 knee prostheses had received either a TKA (primary or revision) (69 in 55 patients), a unicompartimental knee arthroplasty (7 UKA), a RHK (revision −7 in 6 patients) or a megaprosthesis (malignant bone tumours − 28 in 27 patients) (Fig 1). The TKA, UKA and RHK groups were followed prospectively, with serum Co and Cr ions measured preoperatively, at 3,6 and 12 months postoperatively. In patients with a megaprosthesis, metal ions were measured at follow-up (cross-sectional study design). Results (Fig 2 and 3). In primary knees, we did not observe an increase in serum metal ion levels at 3, 6 or 12 months. Two patients with a hip arthroplasty had elevated preTKA Co and Cr levels. There was no difference between unilateral and bilateral knee prostheses. In the revision group, elevated pre-revision levels were found in 2 failures for implant loosening. In both cases, ion levels decreased postoperatively. In revisions with a standard TKA, there was no significant increase in metal ions compared to primary knee arthroplasty. RHK were associated with a significant increase in Co levels even at short-term (3–12 months). The megaprosthesis group had the highest metal ion levels and showed a significant increase in Co and Cr with time in patients followed prospectively. With the current data, we could not demonstrate a correlation between metal ion levels, size of the implant or length of time in situ. Discussion. In primary knee arthroplasty with a standard TKA or UKA, metal ion levels were not elevated till one year postoperatively. This suggests a different mechanism of metal ion release in comparison to metal-on-metal hip arthroplasties. In two cases of revision for implant loosening, pre-revision levels were elevated, possibly associated with component wear, and decreased after revision. With RHK, slightly elevated ion levels were found prospectively. Megaprostheses had significantly elevated Co and Cr levels, due to corrosion of large metallic surfaces and/or wear of components which were not perfectly aligned during difficult reconstruction after tumour resection. Further research is needed to assess the clinical relevance of metal ion levels in knee arthroplasty. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Objectives. Alarm over the reported high failure rates for metal-on-metal (MoM) hip implants as well as their potential for locally aggressive Adverse Reactions to Metal Debris (ARMDs) has prompted government agencies, internationally, to recommend the monitoring of patients with MoM hip implants. Some have advised that a blood ion level >7 µg/L indicates potential for ARMDs. We report a systematic review and meta-analysis of the performance of metal ion testing for ARMDs. Methods. We searched MEDLINE and EMBASE to identify articles from which it was possible to reconstruct a 2 × 2 table. Two readers independently reviewed all articles and extracted data using explicit criteria. We computed a summary receiver operating curve using a Bayesian random-effects hierarchical model. Results. Our literature search returned 575 unique articles; only six met inclusion criteria defined a priori. The discriminative capacity of ion tests was homogeneous across studies but that there was substantial cut-point heterogeneity. Our best estimate of the “true” area under curve (AUC) for metal ion testing is 0.615, with a 95% credible interval of 0.480 to 0.735, thus we can state that the probability that metal ion testing is actually clinically useful with an AUC ≥ 0.75 is 1.7%. Conclusion. Metal ion levels are not useful as a screening test for identifying high risk patients because ion testing will either lead to a large burden of false positive patients, or otherwise marginally modify the pre-test probability. With the availability of more accurate non-invasive tests, we did not find any evidence for using blood ion levels to diagnose symptomatic patients. Cite this article: M. Pahuta, J. M. Smolders, J. L. van Susante, J. Peck, P. R. Kim, P. E. Beaule. Blood metal ion levels are not a useful test for adverse reactions to metal debris: a systematic review and meta-analysis. Bone Joint Res 2016;5:379–386. DOI: 10.1302/2046-3758.59.BJR-2016-0027.R1

Purpose. Total shoulder arthroplasty (TSA) has become a successful treatment option for degenerative shoulder disease. With the increasing incidence in primary TSA procedures during the last decades, strategies to improve implant longevity become more relevant. Implant failure is mainly associated with mechanical or biological causes. Chronic inflammation as a response to wear particle exposure is regarded as a main biological mechanism leading to implant failure. Metal ions released by fretting and corrosion at modular taper connections of orthopedic implants can cause cell-mediated hypersensitivity reactions and might lead to aseptic loosening. Modularity is also commonly used in total shoulder replacement. However, little is known about metal ion exposure in patients following TSA. The objective of this study was to determine in-vivo blood metal ion levels in patients after TSA and to compare blood metal ion levels to control subjects without metal implants. Methods. A total of 19 patients with anatomical total shoulder prosthesis (TSA group) and 20 patients with reverse total shoulder prosthesis (RSA group) who underwent unilateral total shoulder replacement at our hospital between March 2011 and December 2014 with no other metal implant or history of environmental metal ion exposure were recruited for analysis of blood metal ion concentrations of cobalt (Co), chromium (Cr) and titanium (Ti) at a mean follow-up period of 2.3 years (0.7–4.3). For comparison of metal ion concentrations blood samples were obtained in a healthy control group of 23 subjects without metal implants. Ethical approval and informed consent of each patient were obtained for this study. Results. Median cobalt ion levels were 0.14µg/l (range 0.03–0.48) in the TSA group, 0.18 µg/l (0.10–0.66) in the RSA group and 0.11µg/l (0.03–0.19) in the control goup. Median chromium ion levels were 0.34µg/l (0.09–1.26) in the TSA group, 0.48µg/l (0.17–2.41) in the RSA group and 0.14µg/l (0.04–0.99) in the control goup. Median titanium ion levels were 0.86µg/l (0.10–1.64) in the TSA group, 1.31µg/l (0.75–4.52) in the RSA group and 0.62µg/l (0.32–2.14) in the control goup. There was a statistically significant difference in chromium and titanium ion concentrations between both study groups and the control group (see figure 1–3). Conclusion. Patients with unilateral total shoulder replacement demonstrated elevated blood metal ion concentrations. Median blood metal ion levels were higher in the RSA group compared to the TSA group, which could be attributable to the modularity of the reverse total shoulder system. However, overall metal ion levels were relatively low compared to those seen in patients with metal-on-metal total hip replacements. The role of local metal ion exposure in the development of aseptic loosening or hypersensitivity reactions associated with total shoulder arthroplasty should be further investigated. For figures/tables, please contact authors directly.

Objectives. The aims of this piece of work were to: 1) record the background concentrations of blood chromium (Cr) and cobalt (Co) concentrations in a large group of subjects; 2) to compare blood/serum Cr and Co concentrations with retrieved metal-on-metal (MoM) hip resurfacings; 3) to examine the distribution of Co and Cr in the serum and whole blood of patients with MoM hip arthroplasties; and 4) to further understand the partitioning of metal ions between the serum and whole blood fractions. Methods. A total of 3042 blood samples donated to the local transfusion centre were analysed to record Co and Cr concentrations. Also, 91 hip resurfacing devices from patients who had given pre-revision blood/serum samples for metal ion analysis underwent volumetric wear assessment using a coordinate measuring machine. Linear regression analysis was carried out and receiver operating characteristic curves were constructed to assess the reliability of metal ions to identify abnormally wearing implants. The relationship between serum and whole blood concentrations of Cr and Co in 1048 patients was analysed using Bland-Altman charts. This relationship was further investigated in an in vitro study during which human blood was spiked with trivalent and hexavalent Cr, the serum then separated and the fractions analysed. Results. Only one patient in the transfusion group was found to have a blood Co > 2 µg/l. Blood/Serum Cr and Co concentrations were reliable indicators of abnormal wear. Blood Co appeared to be the most useful clinical test, with a concentration of 4.5 µg/l showing sensitivity and specificity for the detection of abnormal wear of 94% and 95%, respectively. Generated metal ions tended to fill the serum compartment preferentially in vivo and this was replicated in the in vitro study when blood was spiked with trivalent Cr and bivalent Co. Conclusions. Blood/serum metal ion concentrations are reliable indicators of abnormal wear processes. Important differences exist however between elements and the blood fraction under study. Future guidelines must take these differences into account

Hip resurfacing arthroplasty (HRA) became a popular procedure in the early 90s because of the improved wear characteristic, preserving nature of the procedure and the optimal stability and range of motion. Concerns raised since 2004 when metal ions were seen in blood and urine of patients with a MoM implant. Design of the prosthesis, acetabular component malpositioning, contact-patch-to-rim distance (CPR) and a reduced joint size all seem to play a role in elevated metal ion concentrations. Little is known about the influence of physical activity (PA) on metal ion concentrations. Implant wear is thought to be a function of use and thus of patient activity levels. Wear of polyethylene acetabular bearings was positively correlated with patient's activity in previous studies. It is hypothesized that daily habitual physical activity of patients with a unilateral resurfacing prosthesis, measured by an activity monitor, is associated with habitual physical activity. A prospective, explorative study was conducted. Only patients with a unilateral hip resurfacing prosthesis and a follow-up of 10 ± 1 years were included. Metal ion concentrations were determined using ICP-MS. Habitual physical activity of subjects was measured in daily living using an acceleration-based activity monitor. Outcome consisted of quantitative and qualitative activity parameters. In total, 16 patients were included. 12 males (75%) and 4 females (25%) with a median age at surgery of 55.5 ± 9.7 years [43.0 – 67.9] and median follow-up of 9.9 ± 1.0 years [9.1 – 10.9]. The median cobalt and chromium ion concentrations were 25 ± 13 and 38 ± 28 nmol/L. A significant relationship, when adjusting for age at surgery, BMI, cup size and cup inclination, between sit-stand transfers (p = .034) and high intensity peaks (p = .001) with cobalt ion concentrations were found (linear regression analysis). This study showed that a high number of sit-stand transfers and a high number of high intensity peaks is significantly correlated with high metal ion concentrations, but results should be interpreted with care. For patients it seems save to engage in activities with low intensity peaks like walking or cycling without triggering critical wear or metal ions being able to achieve important general health benefits and quality of life, although the quality (high intensity peaks) of physical activity and behaviour of patients (sit-stand-transfers) seem to influence metal ion concentrations

Introduction. Dual modular hip prostheses were introduced to optimize the individual and intra-surgical adaptation of the implant design to the native anatomics und biomechanics of the hip. The downside of a modular implant design with an additional modular interface is the potential susceptibility to fretting, crevice corrosion and wear [1–2]. The purpose of this study was to characterize the metal ion release of a modular hip implant system with different modular junctions and material combinations in consideration of the corrosive physiological environment. Methods. One design of a dual modular hip prosthesis (Ti6Al4V, Metha®, Aesculap AG, Germany) with a high offset neck adapter (CoCrMo, CCD-angle of 130°, neutral antetorsion) and a monobloc prosthesis (stem size 4) of the same implant type were used to characterize the metal ion release of modular and non-modular hip implants. Stems were embedded in PMMA with 10° adduction and 9° flexion according to ISO 7206-6 and assembled with ceramic (Biolox® delta) or CoCrMo femoral heads (XL-offset) by three light impacts with a hammer. All implant options were tested in four different test fluids: Ringer's solution, bovine calf serum and iron chloride solution (FeCl3-concentration: 10 g/L and 114 g/L). Cyclic axial sinusoidal compressive load (Fmax = 3800 N, peak load level of walking based on in vivo force measurements [3]) was applied for 10 million cycles using a servohydraulic testing machine (MTS MiniBionix 370). The test frequency was continuously varied between 15 Hz (9900 cycles) followed by 1 Hz (100 cycles). The metal ion concentration (cobalt, chromium and titanium) of the test fluids were analysed using ICP-OES and ICP-MS at intervals of 0, 5·105, 2·106 and 10·106 cycles (measuring sensitivity < 1 µg/L). Results. Due to the additional modular interface between stem and neck adapter the total metal ion release of the modular hip endoprosthesis system increased significantly and is comparable to the coupling of a monobloc stem and a CoCrMo femoral head (Fig. 1). The application of ceramic femoral heads reduced the total cobalt and chromium release in the stem-head taper interface of non-modular and modular stems. In comparison between the four test fluids could be observed that lower pH-values and higher FeCl3-concentrations increased the metal ion release (Fig 2). In contrast, the use of bovine calf serum decreased the metal ion release of modular junctions due to the presence of proteins and other organic components. Discussion. For testing hip implants with proximal femoral modularity according to ISO and ASTM standards, sodium chloride solutions are frequently used to determine the fatigue strength and durability of the stem-neck connection. The present study illustrate that the expansion of standard requirements of biomechanical testing and the use of alternative test fluids is necessary to simulate metal ion release by electro-chemical processes. A promising approach is the use of adapted iron-chloride solutions (10 g/L FeCl3, pH 2) to evaluate the susceptibility of modular hip junctions to fretting, crevice and contact corrosion

In metal-on-polyethylene (MoP) THA large femoral metal heads are designed to increase stability and to reduce dislocation risk. The increased head size could lead to increased taper corrosion with the release of metal ions and adverse reactions. Using blood ion measurements, we aimed to investigate the association between femoral head size and metal-ion release after MoP THA. 96 patients were enrolled at two centers and randomized to receive either a 32-mm metal head or a 36–44 mm metal head (the largest possible fitting the thinnest available polyethylene insert). Blood metal ions and PROMs (OHS, UCLA) were measured at two- and five-year follow-ups. Both 2- and 5-year median chrome, cobalt, and titanium levels were below taper corrosion indicative ion levels. At 5 years, median chrome, cobalt, and titanium levels were 0.5 μg/L (0.50–0.62), 0.24 μg/L (0.18–0.30), and 1.16 μg/L (1.0–1.68) for the 32-mm group, and 0.5 μg/L (0.5–0.54), 0.23 μg/L (0.17–0.39), and 1.30 μg/L (1–2.05) for the 36–44 mm group, with no difference between groups (p=0.825, p=1.000, p=0.558). At 2 years, 7 (32-mm) versus 4 (36–44-mm) patients had elevated ions. At 5 years, 6 (32-mm) versus 7 (36–44-mm) patients had elevated ions. There was no difference in either OHS (p=0.665) or UCLA (p=0.831) between patients with or without elevated blood metal ions. 5 years after the insertion of MoP THAs, we found no differences in the blood metal ion levels between 32 mm heads and 36–44 mm heads and no corrosion-related revisions. As taper corrosion can debut after 5 years, there is still a need for long-term follow-up studies on the association between head size and corrosion in MoP THA

Background. Metal-on-metal hip implants can produce adverse tissue reactions to wear debris. Increased metal ion concentrations in the blood are measured as a proxy to wear and the complications it can trigger. Many studies have examined various factors influencing the metal ion concentrations. This is the first study to investigate the effect of physical activity level, as objectively measured in daily life, on blood ion levels, expecting higher concentrations for higher patient activity. Methods. Thirty-three patients (13F/20M, 55.8 ± 6.2 years at surgery) with a unilateral resurfacing hip prosthesis were included. At last follow-up (6.8 ± 1.5 years) cobalt and chromium concentrations in the blood were determined by inductively coupled plasma mass spectrometry. Physical activity was measured during 4 successive days using a 3D-acceleration-based activity monitor. Data was analysed using validated algorithms, producing quantitative and qualitative parameters. Acetabular cup position was measured radiographically. Correlations were tested with Pearson's r'. Results. Wide ranges in cobalt (10-833nmol/l) and chromium (16-592nmol/l) concentrations were measured. No correlations were found between metal ion concentrations and patient characteristics. The mean time of walking per day of was 5475 ± 2730 seconds (≈ 91 minutes) per day, with 6953 ± 3104 steps made during the day. The cadence, the number of steps per minute, was 99.5 ± 7.4. The subjects performed 41 ± 13 sit-stand transfers per day. The number of peak intensity declines when peaks where more intense. No correlations were found between quantitative or qualitative parameters and metal ion concentrations. Conclusions. Higher metal ion concentrations were not correlated with higher activity levels contrary to original expectations. Based on the results the orthopaedic surgeons is able to reassure his or her patients that physical activity in daily living is presumably safe en does not influence metal ion concentrations. Level of Evidence. 2b. Approval. the ethics committee of the Atrium MC, Heerlen approved this study

Introduction. The MHRA guidelines for metal on metal (MOM) suggest cobalt and chromium levels of more than 7ppb as potential for soft tissue reaction. However, in some patients soft tissue reaction is seen even in the presence of normal serum metal ions levels. Methods. A prospective review of all patients who had metal-on-metal hip arthroplasty was done. Patients who had both serum metal ion levels and MARS MRI scan were included in this study. Results. There were 574 patients with 319 females and 255 males. 240 patients had both MARS MRI scan and serum metal ions. Fifty nine (24.5%) patients with normal metal ions had metallosis/pseudo tumour on MRI scans, and 17 (7%) patients with increased metal ions had normal MRI scans. Conclusion. This study confirms that there is poor correlation between serum metal ions and soft tissue reaction. Nearly a quarter of patients with normal serum metal ions had evidence of metallosis on MRI scan. Clinicians should be aware of the potential for soft tissue reaction even in the presence of normal metal ions. Hence, consideration should be given to further imaging where appropriate, to ensure early metallosis is picked up and further complications of pseudo tumour prevented

The purpose of this randomized controlled trial was to evaluate serum metal ion levels in patients undergoing THA with either a standard or modular dual-mobility bearing. Patients undergoing primary THA for osteoarthritis were randomized to receive either a modular dual-mobility or a standard polyethylene bearing. All patients received the same titanium acetabular and femoral component and a ceramic femoral head. Only patients without a prior history of metal implants in their body were eligible for inclusion, thus isolating serum metal ions to the prosthesis itself. Serum metal ion levels were drawn pre-operatively and at 1 year postoperatively. Power analysis determined that 40 patients (20 in each group) were needed to identify a clinically relevant difference in serum cobalt of 0.35 ng/ml (ppb) at 90% power assuming a pooled standard deviation of 0.31 ppb and alpha=0.05; an additional 30% were enrolled to account for potential dropouts. 53 patients were enrolled, with 22 patients in the modular dual-mobility group and 20 in the standard cohort with data available at one-year. No differences in the serum cobalt (0.17 ppb [range 0.07 to 0.50] vs. 0.19 ppb [range 0.07 to 0.62], p = 0.51) or chromium levels (0.19 ppb [range 0.05 to 0.56] vs. 0.16 ppb [range 0.05 to 0.61], p = 0.23) were identified. At 1 year postoperatively, no differences in serum cobalt or chromium levels were identified with this design of a modular dual mobility bearing when compared to a standard polyethylene bearing

Introduction. Metal-metal surface replacement (MoMSRA) continues to be used in young women. Systemic metal ion release and its effects cause concern. Do metal ions crossing the placenta in pregnant women have potential mutagenic effects? The hypothesis is that metal ions pass freely through the placenta and there is no difference in maternal and cord metal levels. Methods. This is a controlled cross-sectional study of women with MoMSRA. (n = 25, 3 bilateral, mean age 32 years, time from implantation to delivery 60 months). The control group consisted of 24 subjects, mean age 31 years, with no metallic implant and not receiving cobalt/chromium supplements. No patient was known to have renal failure. Whole blood specimens were obtained before delivery and before any infusion or transfusion, and cord blood specimens immediately after delivery. Results. Cobalt and chromium were detectable in all specimens in both cohorts. In the control group, the difference between maternal and cord levels was only 5 to 7% indicating free passage. Study group cord cobalt (0.88 mg/L) and chromium levels (0.34 mg/L) were significantly lower than maternal cobalt (1.57 mg/L, p < 0.05) and chromium Levels (1.43 mg/L, p 0.05). However there is a significant difference between the cord cobalt levels in the study (0.88 mg/L) and control (0.41 mg/L, p < 0.05) groups. Discussion and Conclusion. The limitation of this study is that none of the patients in the study had the excessive metal ion levels recorded in recent times in some of the withdrawn resurfacing arthroplasties. The differences between maternal and cord metal ions in the controls indicate that normally the placenta allows an almost free passage of metal ions. Within the range of levels studied, the relative levels of metal ions in the maternal and cord blood in the study group reveal that the placenta exerts a regulatory influence on metal ion transfer

High short-term failure rates have been observed with a number of metal-on-metal (MoM) hip designs. Most patients require follow-up with blood metal ions, whichprovide a surrogate marker of in-vivo bearing wear. Given these results are used in clinical decision making it is important values obtained within and between laboratories are reproducible. To assess the intra-laboratory and inter-laboratory variability of blood metal ion concentrations analysed by four accredited laboratories. Whole blood was taken from two participants in this prospective study. The study specimen was obtained from a 42 year-old female with ceramic-on-ceramic hip arthroplasty failure resulting in unintended metal-on-ceramic wear and excessively high systemic metal ion levels. The control specimen was from a 52 year-old healthy male with no metal exposure. The two specimens were serially diluted to produce a total of 25 samples with different metal ion concentrations in two different anticoagulants each. Thus 50 samples were sent blinded in duplicate (total 100) to four accredited laboratories (A, B, C, D) to independently analyse blood metal ion concentrations. Ten commercially available reference specimens spiked with different amounts of metal ions were also obtained with known blood metal ion concentrations (range for cobalt 0.15µg/l-11.30µg/l and chromium 0.80µg/l to 37.00µg/l) and analysed by the four laboratories. The intra-laboratory coefficients of variation for repeat analysis of identical patient specimens were 7.32% (laboratory A), 4.64% (B), 7.50% (C), and 20.0% (D). The inter-laboratory variability for the analysis of all 25 samples was substantial. For the unmixed study specimen the laboratory results ranged from a cobalt of 263.7µg/l (D) to 525.1µg/l (D) and a chromium of 13.3µg/l (D) to 36.9µg/l (A). For the unmixed control specimen the laboratory results ranged from a cobalt of 0.13µg/l (B) to 0.77µg/l (D) and a chromium of 0.13µg/l (D) to 7.1µg/l (A). For one of the mixed specimens the laboratory results ranged from a cobalt of 12.50µg/l (A) to 20.47µg/l (D) and a chromium of 0.73µg/l (D) to 5.60µg/l (A). Similar inter-laboratory variation was observed for the other mixed samples. The true mean (standard deviation) of the 10 commercial samples was 4.48µg/l (4.20) for cobalt and 8.97µg/l (10.98) for chromium. This was similar to the values obtained by all four laboratories: mean (standard deviation) cobalt ranged from 3.54µg/l (3.17) in laboratory A to 4.35µg/l (4.13) in laboratory D, and chromium ranged from 7.76µg/l (9.50) in laboratory B to 9.55µg/l (9.16) in laboratory A. When testing patient samples, large variations existed both between and within four laboratories accredited to perform analysis of blood metal ion concentrations. However, this was not the case when assessing commercially spiked samples which are regularly used to validate laboratory testing. This is of great clinical concern and could lead clinicians to either recommend unnecessary revision or delay surgery, with both having the potential to adversely affect patient outcomes. It is recommended that laboratories use patient samples to assess the accuracy and reproducibility of the analyses performed. This may also assist in explaining the variations observed in this study

Introduction. Mechanical or corrosive failure of total knee arthroplasties (TKAs) is difficult to diagnose with current laboratory and radiographic analyses. As such, the goal of this study was to determine the mean blood concentration of cobalt, chromium, and titanium in a series of revision TKAs with mechanical implant failure and evaluate whether they facilitated identification of the underlying TKA failure mechanism. Methods. Serum cobalt, chromium, and titanium levels and synovial fluid characteristics were evaluated in 12 patients (13 aseptic revision TKAs) who underwent revision TKA between 2000 and 2020 at a single academic institution for mechanical implant failure or corrosion. Seventy-five percent were re-revisions of previously revised TKAs. Mean time to revision was 6 years. Modular metallic junctions were present in 100%. Twenty-five percent did not have another in situ total joint arthroplasty, and the remaining patients did not have a metal-on-metal articulation that could lead to elevation in serum metal ion levels. Mean follow-up after the revision TKA was 8 months. Results. Mean serum cobalt, chromium, and titanium concentrations were 11 ng/mL, 6 ng/mL, and 3 ng/mL, respectively. Serum metal ion levels facilitated failure mechanism identification in 75%, which included modular junction failure (6 cases), constraint locking mechanism failure (3 cases), corrosion of modular metallic interfaces (2 cases), and implant fracture (1 case). Arthrocentesis was performed in 75%. Mean synovial fluid cell count was 950 cells/mcL. Monocytes were the predominant mean cell type (41%), followed by neutrophils (35%), and lymphocytes (22%). Conclusion. Serum metal ion assessment should be considered when the etiology of painful primary or revision TKAs, particularly those with modular metallic junctions, remains elusive after routine evaluation

Introduction. Metal on metal (MoM) bearings have been dealt a severe blow in the past few years. The release of metal ions may have arisen from corrosion, wear, or a combination of the two. Edge loading due to implant malposition is thought to cause a failure of lubrication and to contribute to excessive wear and increased metal ion release [1]. Literature reports aseptic lymphocytic vasculitis-associated lesions (ALVAL) are associated with a variety of failures which occur to some degree in all implanted metal femoral components [2, 3]. Moreover, Willert et al [4] has described ALVAL in non-MoM bearing designs too. This paper has investigated the metal ion release due to total hip replacement (THR), Hip Resurfacing (HR) and total knee replacement (TKR). Methods. Following human ethics approval 200 patients were enrolled in this single surgeon randomised controlled study. The treatment groups were total knee replacement (TKR) (n=100), HR (n=50) and THR (n=50). Serum cobalt (Co) and chromium (Cr) ion levels were taken preoperatively for baseline measurement then at 6 month, 1 year and 2 years postoperatively. Results. A preliminary observation of the data was performed to investigate the release trend of the Metal Ions (Figs 1 & 2). Initially there is a significant difference (p<0.05) between TKR and THR for the 6 month ion levels. At the 1 year time-point there is no difference between the TKR and THR for Cr levels. However, there is a significant difference (p<0.05) between TKR and HR for Cr levels at the 1 year time-point and a highly significant difference (p<0.001) between TKR, THR and HR for Co levels at 1 year. At the 2 year time-point there is no difference (p>0.05) between the TKR and THR for Cr levels. However, there is still a highly significant difference (p<0.001) between TKR, THR and HR for Co levels at 2 years. There was no significant difference detected between THR and HR (p>0.05) for both Co and Cr levels at all time-points. Discussion and Conclusion. All patient metal ion levels were in the safe range. Whilst there are other reported studies comparing the effect of head diameter of MoM bearings on systemic release of metal ions, this is the first paper to compare MoM hip bearings with TKR bearings. There was no difference between the release of Cr levels for the TKR and THR at the 2 year time-point. The trend of metal ion release is similar for all implants. However, THA deviates from HR at the 12 month time-point for Co levels. This paper demonstrates that surgical technique plays an important role in metal ion release and the long term integrity of a MoM bearing

Purpose. There is a postulated association between increased serum metal ions and pseudotumour formation in patients with metal-on-metal hip replacements. The primary aim of this study was to assess the prevalence of pseudotumour in 31 asymptomatic patients with a large femoral head (LFH) metal-on-metal hip implant. This was compared to the prevalence of pseudotumour in 20 matched asymptomatic patients with a hip resurfacing (HRA) and 24 matched asymptomatic patients with a standard metal-on-polyethylene (MOP) total hip. A secondary objective was to assess possible correlation between increased serum metal ions and pseudotumour formation. Method. Ultrasound examination of the three groups was performed at a minimum follow up of two years. Serum metal ions were measured in the metal-on-metal LFH and HRA groups at a minimum of two years. Results. There were 10 (32%) solid or cystic masses in the LFH group with a mean size of 89.3 (8 to 437) cm3. In the HRA group there were five (25%) masses with a mean size of 41.6 (6 to 119) cm3. In the MOP group there was one cystic mass measuring 9.8 cm3. Median serum cobalt and chromium ion levels in the LFH group were 4.50 gL (interquartile range, 2.38 to 7.47) and 2.82 gL (interquartile range, 1.48 to 3.18) compared to 0.83 gL (interquartile range, 0.65 to 1.12) and 1.08 gL (interquartile range, 0.78 to 1.31) in the HRA group. Conclusion. This study demonstrates a significantly higher prevalence of pseudotumours in patients with large head metal-on-metal total hips. The higher levels of metal ions in this group suggest that elevated metal ions may lead to pseudotumour formation

This study evaluates metal ion levels in patients enrolled in a prospective evaluation of hip resurfacing arthroplasty utilizing the Conserve Plus implant (Wright Medical Technology). Serum, urine and erythrocyte metal ion levels were assessed preoperatively and postoperatively. Average levels at three months were 24 nmol/l for cobalt and 40 nmol/l for chromium. These increased to 40 nmol/l for cobalt and 80 nmol/l for chromium at the six-month mark. The clinical significance of increased metal ion levels is yet to be determined. To evaluate the clinical, functional and radiographic outcome of hip resurfacing arthroplasty utilizing the Conserve Plus implant (Wright Medical Technology). Serum, urine and erythrocyte metal ion levels were evaluated both pre and postoperatively. Ion levels for both cobalt and chromium increased from the three-month to the six-month mark postoperatively and were significantly elevated relative to preoperative values. This study helps to establish a baseline for metal ion levels following hip resurfacing arthroplasty. Serum, urine and erythrocyte metal ion levels were assessed preoperatively and postoperatively. All levels were within normal range preoperatively. Average serum levels at three months were 24 nmol/l for cobalt and 40 nmol/l for chromium. These increased to 40 nmol/l for cobalt and 80 nmol/l for chromium at the six-month mark. Average erythrocyte metal ion levels at three months were 0.92 ug/l for cobalt and 1.8 ug/l for chromium. The average erythrocyte levels at six months were 1.3 ug/l for cobalt and 2.0 ug/l for chromium. A prospective multi-center study to evaluate the outcome of hip resurfacing arthroplasty was initiated in July 2003. Each patient was evaluated preoperatively and postoperatively with outcome scores, radiographs as well as serum, urine and erythrocyte metal ion levels. The results of this prospective evaluation show a rise in ion levels from three to six months postoperatively. Further follow-up is necessary to assess future trends with respect to the ion levels as well as the clinical significance. Funding: This study has been sponsored in part by Wright Medical Technology

Introduction: The accepted method of assessing wear following a hip simulator test has been to use a precision balance. As the MoM devices produce significantly less weight loss than hard-on-soft bearings, the measurements of MoM devices are now almost at the detection limit of many balances. There is a need for a method that can be used in conjunction with gravimetric analysis that will provide an accurate assessment of ion concentration levels that will support the gravimetric measurements. Aim: To develop a method to assess wear using metal ion analysis in order to support gravimetric measurements of metal on metal devices. Materials and methods: Hip simulator test: Three pairs of 50 mm diameter as cast CoCr MoM devices were tested in a ProSim hip wear simulator (SimSol Stockport/UK) under physiologically relevant conditions. The lubricant was new born calf serum with 0.2 % sodium azide concentration diluted with de-ionised water for protein concentration of 20 g/l. Stop-start motion was implemented every 100 cycles. Lubricant changed every 125 k cycles. The frequency was 0.5 Hz. Wear was assessed gravimetrically at every 0.5 million cycles (Mc) interval. Ion analysis: Serum was collected from test station and allowed to settle for 12 hours. An aliquot of 20 ml from lubricant was collected. Each sample was centrifuged at 2500 g-force for 10 minutes. A 10 ml aliquot was collected from each sample and was further centrifuged at 2500 g-force for 10 minutes. 1.5 ml aliquot was collected and stored at −20 °C. A high resolution inductively-coupled plasma mass spectrometry instrument (ELEMENT, ThermoFinnigan MAT, Bremen/Germany) was then used for the analysis of metal ions. Results and Discussion: The average cumulative metal ion levels at 0.5, 1 and 1.5 Mc showed similar trends in wear to that of the average cumulative weight loss assessed gravimetrically. There were similar biphasic wear trends in both metal ion levels and gravimetric weight losses. Other studies have also shown similar correlation between volume loss and ion concentration levels. The percentage distribution of Co, Cr and Mo in the metal ion samples are in close agreement with nominal chemical composition of the material tested. Conclusion: This study showed that metal ion measurements can help to confirm gravimetrically measured material loss