Objectives. Several studies have reported elevated blood cobalt (Co) and chromium (Cr) concentrations in patients with total knee replacements (TKRs). Up to 44% of tissue samples taken from patients with failed TKRs exhibit histological evidence of metal sensitivity/ALVAL. In simulated conditions, metal particles contribute approximately 12% of total wear debris in TKR. We carried out this investigation to determine the source and quantity of metal release in TKRs. Design and Methods. We analysed 225 explanted fixed-bearing TKRs (Attune, Genesis II, NexGen, PFC, and Vanguard) revised for any indication. These were analysed using peer-reviewed [coordinate measuring machine (CMM)] methodology to measure the volumetric wear of the polyethylene (PE) bearing surfaces and trays. The trays were analysed using 2D profilometry (surface roughness-Ra) and light microscopy. Histological and blood metal ion concentration analyses were performed in a sub-sample of patients. Results. The median (IQR) PE wear rate was 14 (6 to 20) mm. 3. /year. Microscopic examination of the superior surface of trays exhibited pitting on 132 (59%) of trays. There was a statistically significant (p<0.05) increase in Rvk on the pitted area of trays for each design, indicating material removal from the pits compared to the unpitted area. The inferior surface of 116(51%) of trays displayed polishing, indicative of abrasive wear. The median(range) Co and Cr concentrations were 2.5µg/l (0.2–69.4) and 1.7µg/l (0.5-12.5) respectively in 40 patients. Of the tissue samples examined in 30 patients, 6 had at least “mild”-ALVAL infiltrate. All corresponding “ALVAL” explants were found to be pitted and/or show evidence of loosening of the tray. Conclusion. This study provides further evidence that CoCr release in TKR appears to be an under-appreciated cause of adverse clinical outcomes. The generation of metal particles was predominantly from the metal tray, which may explain elevated metal ions after TKRs, despite no direct metal-on-metal contact

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

Local and systemic concentrations of cobalt (Co) and chromium (Cr) ions may be elevated in patients with accelerated tribo-corrosion at prosthesis bearing surfaces and modular taper junctions. Previous studies by us and others have shown that exposure to these metals negatively affect the viability and function of osteoblasts and osteoclasts in vitro, with implications for bone health. More recently, we have observed an increase in total bone mineral density and reduced bone turnover (TRAP5b and osteocalcin) in patients with well-functioning metal-on-metal hip resurfacing (MOMHR). Here, we provide data to support the hypothesis that osteoclast differentiation and function is altered in this patient population, and that this effect is transferrable through their serum. Patients with well-functioning MOMHR (n=18) at median follow-up of 8 years were individually matched for gender, age and time-since-surgery to a low-exposure group consisting of patients with metal-on-polyethylene total hip arthroplasty (THA). The median circulating concentrations of Co and Cr for the MOMHR group were 2.53µg/L and 2.5µg/L respectively, compared to 0.02µg/L and 0.03µg/L for the THA group. Monocyte fraction of peripheral blood was isolated from these patients, seeded onto dentine wafers and differentiated into osteoclasts using media supplemented with RANKL and M-CSF (osteoclastogenic media, OM). Cultures were monitored for the onset of resorption, following which they were treated with OM, autologous serum or serum from the other individual within the matched MOMHR - THA pair, all supplemented with RANKL and M-CSF. At the end of the culture, cells were TRAP stained and quantified for total osteoclast number, number of resorbing osteoclasts and percentage resorption using the CellD Software Package (Olympus, Southend-on-Sea, U.K.). For cells differentiated in osteoclastogenic media, the resorbing ability of osteoclasts derived from MOMHR patients was reduced by 30% (P=0.046) compared to THA. Correlation analyses showed that chronic exposure to Co and Cr trends towards negative association with resorption ability of these osteoclasts (r = −0.3, P=0.06). Furthermore, the resorbing ability of osteoclasts generated from MOMHR patients and differentiated in autologous serum was reduced 33% (p < 0 .0001), whilst matched THA serum caused a smaller reduction of 14% (p < 0 .01). When cells derived from THA patients were differentiated in autologous serum, the resorbing ability of osteoclasts was similarly reduced by 35% (p < 0 .0001), whilst the matched MOMHR serum also caused a reduction of 21% (p < 0 .0001). Reduced osteoclastogenic response of precursor cells from patients with higher circulating Co and Cr suggests an inherent change in their potential to differentiate into functional osteoclasts. The data also suggests that functional response of mature osteoclasts generated from patient precursor cells are dependent on the prior systemic metal concentrations and the presence of higher circulating CoCr in patients with MOMHR. These effects are modest, but may explain the subtle increase in systemic bone mineral density and decreased bone turnover observed in patients after 8 years exposure compared to age, sex, and exposure-time matched patients who received a conventional THA

Introduction. Mechanically assisted crevice corrosion (MACC) in metal-on-polyethylene (MOP) total hip arthroplasty (THA) is of concern, but its prevalence, etiology and natural history are incompletely understood. Methods. From January 2003 to December 2012, 1356 consecutive THA surgeries using a titanium stem, cobalt chromium alloy femoral head, highly crosslinked polyethylene and a tantalum or titanium acetabular shell were performed. Patients were followed at 1 year, and 5 year intervals for surveillance, but also seen earlier if they had symptoms. Any patient with osteolysis or unexplained pain underwent exam, radiographs, CBC, ESR and CRP, as well as serum cobalt (Co) and chromium (Cr) level. MARS MRI was performed if the Co level was > 1 ppb. Results. Symptomatic MACC was present in 39/1356 patients (2.9%). Yearly MACC prevalence ranged from 0 % (0/139, 2005) to 9.9 % (16/162, 2009). 22/39 (56%) patients have undergone revision surgery, and 17/39 (44%) have opted for ongoing surveillance. Of the surveillance patients, serial serum metal ion levels appear to increase over time. Time of symptoms is correlated with tissue necrosis at time of revision. Conclusions. The prevalence of MACC in MOP hips is higher in this cross-sectional study than previously reported. The highest prevalence was found in 2009 with this vendor. Based on how common this finding is in symptomatic patients from 2009, we may consider asking asymptomatic patients to obtain baseline serum ion levels. The goal of our ongoing research is to understand how to avoid permanent soft tissue loss from adverse local tissue reactions caused by MACC

Hip resurfacing offers an attractive alternative to conventional total hip arthroplasty in young active patients. It is particularly advantageous for bone preservation for future revisions. Articular Surface Replacement (ASR) is a hip resurfacing prosthesis manufactured by DePuy Orthopaedics Inc. (Warsaw, IN). The manufacturer voluntarily recalled the ASR system in 2010 after an increasing number of product failures. The present study aimed to determine the long-term results in a large cohort of patients who received the ASR prosthesis. Between February 2004 and August 2010, 592 consecutive hip resurfacings using the ASR (DePuy Orthopaedics Inc., Warsaw, IN) resurfacing implant were performed in 496 patients (391 males and 105 females). The mean age of the patients at the time of the surgery was 54 (range: 25 to 74) years. Osteoarthritis was the most common diagnosis in 575 hips (97.1%). The remaining patients (2.9%) developed secondary degenerative disease from ankylosing spondylitis, avascular necrosis, developmental hip dysplasia, and rheumatoid arthritis. Clinical and radiographic information was available for all patients at the last follow up. Cobalt (Co) and chromium (Cr) levels were measured in 265 patients (298 hips) by inductively coupled plasma-mass spectrometry (ICP-MS). The average follow up of the study was 8.6 years (range: 5.2 to 11.6 years). The mean Harris hip and UCLA scores significantly improved from 44 and 2 pre-operatively to 85.3 and 7.1 respectively. The median Co and Cr ion level was 3.81 microgram per liter and 2.15 microgram per liter respectively. Twenty-seven patients (5.4%) were found to have blood levels of both Co and Cr ions that were greater than 7 microgram per liter. Fifty-four patients (9.1%) were revised to a total hip arthroplasty. Kaplan-Meier survival analysis showed a survival rate of 87.1% at 8.6 years with revision for any cause and 87.9% if infection is removed. A significantly higher survival rate was observed for the male patients (90.2%, p <0.0001) and for the patients with ASRs with femoral heads diameters larger than 52 mm (90.1%, p=0.0003). This study confirms that patient selection criteria are of great importance to the overall survivorship of hip resurfacing arthroplasty. Improved clinical results have been reconfirmed with the use of larger diameter femoral heads

Introduction:. Whole blood metal ion level and clinical outcomes of ceramic-on-metal bearing were comparable to ceramic-on-ceramic THA in this prospective randomized controlled trial. Methods:. We randomized 150 consecutive THA cases at one institution into two groups: Group I and Group II. Group I, 75 cases, received a THA using ceramic-on-metal couplings and Group II, 75 cases, received ceramic-on-ceramic bearing THA. The implant differed only in the bearing surfaces used. We compared the serum levels of cobalt (Co) and chromium (Cr) and functional outcome scores preoperatively, and at 2, 6, and 12 months postoperatively. Results:. The demographics and preoperative Co and Cr levels were similar between the groups. Femoral head size measured 32 and 36 mm and the proportion of each size was similar in both groups. The mean serum cobalt and chromium levels increased significantly at 2 months in Group I (Co p = 0.02, Cr p = 0.04), but no differences noted between groups at 6 and 12 months (Co p > 0.05, Cr p > 0.05). The mean WOMAC hip scores showed comparable improvements at 12 months with no difference between groups. No ceramic fracture has occurred during follow-up period. Discussion & Conclusion:. CoM bearing THA has showed the metal ion levels and the clinical results comparable to CoC couples except for the relatively high metal ion in running-in period

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.

Background:. Potential systemic toxicity of metal ions from metal-on-metal hip arthroplasties (MoMHA) is concerning. High blood cobalt (Co) levels have been associated with neurological, cardiac and thyroid dysfunctions. Questions/purposes:. The aim of this research was to investigate the prevalence of systemic Co toxicity in a MoMHA population, to identify confounding factors, and to indicate a Co level above which there is a high risk for systemic toxicity. Patients and Methods:. We conducted a cross-sectional study of patients with a MoMHA, using questionnaires validated to detect cobaltism in cobalt industry workers. We retrospectively identified 161 patients with Co levels >4 μg/L and 337 patients with Co levels <4 μg/L and collected 385 completed questionnaires. There were 207 men and 178 women with a mean age of 60 years (24–86). Mean follow-up was 5.7 years (1 to 13). Co levels were subdivided into <4 μg/L, 4–10 μg/L, 10–20 μg/L and >20 μg/L groups. Results:. There were significant correlations (p ≤ 0.003) between increasing Co levels and prevalence of sleeping disorders, cognitive problems, equilibrium disturbances, neuropathic symptoms, fatigue, somatic disorders and mood changes. More frequent and severe symptoms were found with Co > 20 μg/L (p = 0.017). Several years post-revision, some patients still complained of chronic symptoms possibly associated with longer exposure. Female gender and age ≤50 years were confounding factors. Conclusions:. We demonstrated a correlation between increasing Co levels and toxicity symptoms (p ≤ 0.003). As in the published case reports of MoMHA related cobaltism, the highest incidence of symptoms was found with Co > 20 μg/L. Patients with repeated Co measurements >20 μg/L are at risk for systemic toxicity

Background:. The Rejuvenate modular neck stem (Stryker, Mahwah, NJ) was recently recalled due to corrosion at the neck-stem junction. The purpose of this study was to investigate the rate of corrosion related failures and survivorship of this implant, and analyze the correlation between the implant and patient factors with serum metal ion levels. Material and Methods:. Between June 2009 and July 2012, 123 Rejuvenate stems (97 modular and 26 non-modular) THAs were implanted in 104 patients by a single surgeon via a modified anterolateral approach. Serum Cobalt (Co) and Chromium (Cr) levels (microgram per liter [μg/L]) were obtained in all patients. In cases of elevated serum metal ion levels or symptomatic hip, patients underwent magnetic resonance imaging (MRI) for assessment of osteolysis or adverse local tissue reactions (ALTR). Correlation between implant factors (implant size, head size, head length, offset), patient factors (age, gender, BMI) with serum metal ion levels and revisions were analyzed using logistic regression models. Results:. The mean follow-up was 2.7 ± 0.6 years. The mean Co and Cr levels were 5.4 ± 5.7 μg/L (0.2–31) and 2.1 ± 1.5 μg/L (0.1–4.3), respectively. The differences between the Co and Cr levels in the two groups were statistically significant. 49% of THAs in the modular group had elevated metal ion levels (> 4.0 μg/L). There was a significant correlation between higher metal ion levels, younger age, and higher offset (p < 0.05). Presence of pain and high cobalt levels were significant predictors for revision surgery. The rate of revision at the time of this study was 26%, the majority were in the 2. nd. year after surgery. The Kaplan-Meier survivorship was 75% at the time of this study. Discussion and Conclusions:. The short-term high rate of corrosion related revision with Rejuvenate modular neck stems is extremely alarming. We anticipate more revisions in the near future. Level of Evidence: Level III, Therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence

Introduction. Revision of total hip replacements (THRS) is predominantly due to aseptic loosening, pain and infection [1]. The current method used to address the risk of infection is to administer antibiotics and to include antibacterial agents into bone cement (if used) and on implant coatings [2–4]. Currently, silver (Ag) coatings have only been applied to titanium hip stems [3]. Cobalt chromium alloy (CoCr) is a widely used orthopaedic alloy which is commonly used as a bearing surface; revisions of joints using this material often describe adverse reactions to the particulate wear debris [1]. This study considers an Ag containing CrN based coating on a CoCr substrate with the aim to reduce cobalt (Co) release and promote antibacterial silver release. Methods. Silver Chromium Nitride (CrNAg) coatings were developed and applied onto the bearing surfaces of 48 mm diameter metal-on-metal THRs. Three coatings were evaluated: high Ag at the surface (CrNAg+), low Ag at surface (CrNAg-) and uniform Ag (CrNAg=). All bearings were tested under ISO 14242-3 conditions for 0.17 million cycles (mc) representing approximately 2 months use in vivo. Wear was determined gravimetrically; Ag and Co levels in the lubricant were measured using graphite furnace atomic absorption spectroscopy. Testing of the CrNAg= bearings were continued to 2mc under standard conditions; CrNAg- bearings to 5mc incorporating lateralisation, which created separation at swing phase and rim contact at heel strike. Wear volume and Ag/Co release were monitored at 0.33, 0.67, 1mc and every mc thereafter. Results. All bearings produced low levels of wear and released silver into the lubricating fluid. An increase in silver concentration at the surface of the bearings was found to increase both the silver released and wear, Figure 1. Negligible cobalt was released. Testing of the CrNAg= coating to 2mc showed the wear rate to decrease after 0.17mc, Figure 2. Ag release continued up to 2mc but at a decreased rate. The CrNAg- coating tested under lateralisation conditions to 5mc showed no coating failure and negligible cobalt release. Wear and silver release showed similar patterns and reached a steady state after 1mc, Figure 3. Discussion. The AgCrN coatings on bearing surfaces of a hip joint are capable of releasing Ag at concentrations within the ‘No Observable Adverse Effect Limit’ [5]. These coatings also prevented Co release while maintaining a low wear rate. All coatings remained intact and did not delaminate, even under adverse conditions. These coatings have been tested in a metal-on-metal hip bearing surface, the most controversial and challenging condition for a coating, wearing against itself. CoCr is used as a bearing surface against polyethylene in hips and knees, in stems and tapers, as tibial trays in knee replacement and as shells for acetabular cups. This coating may be applied to a wide range of applications, removing some of the challenges over the use of CoCr while reducing infections

INTRODUCTION. Systemic levels of metal ions are surrogate markers of in-vivo wear of metal-on-metal hip resurfacings (MoMHRA). The wear-related generation of metal ions is associated with component size and positioning but also with design specific features such as coverage angle, clearance, metallurgy and surface technology. OBJECTIVES. The objective of the study was to investigate whether a hip resurfacing design (ACCIS) with TiNb engineered bearing surfaces would generate less chromium (Cr) and cobalt (Co) ions during and after the run-in phase of wear and whether Ti ions could be detected indicating wear of the coating. METHODS. Whole blood and serum Cr, Co and Ti levels were measured at 3, 6, 12, 24 and 60 months (ICP-MS). RESULTS. The Cr and Co levels were virtually untraceable during the running-in phase till 1 year. After that, there was a significant increase at the 2 years interval and further at the 5 years interval for both Cr and Co. Overall mean 5 years concentrations of Cr 4.8 μg/l (range 0.5–10.5 µg/L) and Co 4.3 μg/l (range 0.7–12.1µg/l)) had evolved above the established acceptable upper limits (Cr < 4.6 μg/l - Co < 4.0μg/l). 1. Elevated whole blood Ti levels were demonstrated in all patients (mean levels of 9.16 μg/l, 12.54 μg/l and 9.17 μg/l at 3,6 and 12 months respectively) with a peak level at 6 months although there was no statistical difference between the measurements at 3, 6, 12 and 24 months. DISCUSSION. These findings correspond with a release of Ti ions from the TiNb surface during the running-in phase. The whole blood Ti levels were higher compared to whole blood Ti levels in the literature for uncemented grit-blasted acetabular and femoral MoMTHA components and Ti plasma spray coated MoMHRA acetabular components. In those reports, the Ti release is due to passive corrosion from non-articulating surfaces (acetabular and/or femoral fixation surfaces) and is thus likely to be less elevated compared to release due to articulating surface wear as with the ACCIS HRA. A remarkable finding was the continuous elevation of Cr and Co ion levels after the TiNb coating seems to have been worn off. This may be due to a change in clearance as the head is slightly migrating into the cup because of the worn-off coating at the cup-head contact area. CONCLUSION. The ACCIS design has no traceable Cr and Co ions in the running in phase because of its TiNb ceramic surface coating that prevents Cr and Co release. Once the coating is worn off, which only happens at the patch area of friction, a release of Co and Cr ions starts. Although TiNb coating allegedly protects the CoCrMo surface from corrosion by acting as a seal, Cr and Co ions continued to increase at 5 years indicating further wear possibly as a result of change in clearance

Introduction. Failure of total knee arthroplasty (TKA) is mainly caused by biological reactions against wear particles generated at the implant. So far, wear has been mainly attributed to polyethylene (PE) and much effort has been put into understanding and optimizing the wear mechanism of PE in recent years. However, evaluation of metal wear particles and ion release in TKR has been neglected so far although the implants present large metal surface areas. In the present study we aimed to analyse the wear performance of TKA and to study the kinetics of metal ion and particle release. We hypnotized that due to abrasion and corrosion TKA will release relevant levels of Cobalt (Co), Chromium (Cr), Molybdenum (Mo) and Titanium (Ti). Methods. Implants were subjected to an in-vitro simulation applying physiological loadings and motions for 5 million walking cycles. Wear processes were determined gravimetrically and by measuring the release of Co, Cr, Mo and Ti ions using HR-ICP-MS. Surface alterations were determined through surface roughness measurements. Results. An average PE wear rate of 7.28 mg/10. 6. cycles (R=0.995;p≤0.001) was determined. After 5 million cycles the cumulative release of metals measured 1.63 ± 0.28mg for Co, 0.47 ± 0.06mg for Cr, 0.42 ± 0.06 mg for Mo and 1.28 ± 0.14mg for Ti. The metal release progressed linearly and the rate of sole surface corrosion was 0.06mg/10. 6. cycles (R=0.993;p≤0.001), whereas the rate of articulation induced metal release was found to be 0.80mg/10. 6. cycles (R=0.996;p≤0.001), (Fig. 1). Discussion. For other metallic implant devices it is well known that metal wear products are able to interact with the immune system potentially leading to immunotoxic effects like hypersersensitivity or the formation of pseudotumors. To our knowledge, this is the first study that analysed the release of metallic wear products in TKA in vitro. We found that approx. 10% of the whole wear products are metallic and we believe that these particles and ions are relevant. Their effect regarding the clinical outcome of TKR will be analysed in further studies

Bearing diameter and acetabular component orientation have been shown to be important variables effecting blood metal ion levels following hip resurfacing arthroplasty. So far no studies on bilateral hip resurfacings have taken into account these variables. We examined the serum ion results of patients under the care of two experienced hip resurfacing surgeons who carry out ion analysis as part of routine post operative care. Surgeon 1: Patients were implanted exclusively with a “third generation” resurfacing device. Surgeon 2: Patients were implanted with the same “third generation” device and also a low clearance “fourth generation” resurfacing device. Only ion results from patients who were 12 months post surgery were included. Bilateral patients were matched to unilateral patients according to the surgeon performing the operation; the resurfacing system implanted and cup inclination and anteversion angles. The ion data from each bilateral group was tested against the corresponding unilateral groups using the Mann Whitney U test for non parametric data. Significance was drawn at p<0.05. Surgeon 1: There were 310 patients with unilateral joints and 50 with bilateral joints. There were no significant differences with regard to time to follow up, activity levels, joint sizes or cup orientations. Serum chromium (Cr) and cobalt (Co) concentrations were significantly greater in the bilateral group (p<0.001). Median ion levels were greater in the bilateral group by a factor of >2 in the smallest joint sizes and <2 in the largest joints. Surgeon 2: There were 11 patients with bilateral third generation resurfacing joints and 50 with unilateral joints of the same design. The same relationship as described above was identified. There was a notable difference in the fourth generation implant group (n=13 bilateral, n=100 unilateral). Median ion levels for patients receiving bilateral joints of sizes <47mm were ten times greater than in the corresponding unilateral group. Bearing diameter and component design are critical factors in determining metal ion levels following bilateral hip resurfacings. Surgeons must consider the potential implications of gross increases in metal ion levels prior to performing bilateral hip resurfacings in smaller patients

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

Introduction. There has been much discussion in the literature concerning the possible detrimental effects of metal ion circulating in the body after MOM THR. This study seeks to evaluate the differences in observed Co and Cr levels in blood after TKR and several popular THR options. Method. We compared chromium (Cr) and cobalt (Co) levels between three different hip replacement bearings and total knee replacements (TKR) over time. Blood samples were taken from patients who received metasul 28 mm (n=25), metasul 32 mm (n=25) and Durom (n=50) hip bearings and TKR (n=100), pre- operatively and post operatively at six, twelve and twenty-four month intervals. Blood samples were analysed for Co and Cr levels using ICPMS (Inductively coupled mass spectrometry) and reported as parts per billion. Results were compared using Kruskal-Wallis Test (nonparametric ANOVA). Results. No increase was seen in serum Co and Cr levels in TKR patients over time. There were statistically significant differences in Co levels between the TKR group and all bearing surfaces of THR (28, 32 mm and Durom), p<0.001 at two years. Cr levels were significantly higher (p<0.001) in Durom bearings vs TKR only at one year decreasing to p<0.01 at two years. Comparing ion levels over time in the hip group, only in the Durom cohort did serum Cr levels preop vs 12 and 24 months reach a statistical significance of p<0.001. For Co, all three bearings showed a statistically significant increment over time (p<0.01). Highest levels of ions were seen with the 28 mm bearings but comparison between the three THR bearings at two years showed no statistical difference in Cr or Co levels. Median blood Cr concentration did not exceed 1.6 ppb in any subgroup. All median Co concentrations were below 0.8ppb. Conclusions. Over a two-year period Co and Cr levels for TKR did not differ appreciably from preoperative levels. Both Cr and Co levels were only mildly elevated post THR for all bearings. Metasul 28 mm bearings require further follow-up as the Co levels were not seen to plateau at two years

Purpose. To determine whether there is a difference in the metal ion levels among three different metal-on-metal total hip systems: two monoblock large heads and one modular metal-on-metal total hip replacement system in patients who received these implants in our region. Method. A group of 56 patients were recruited that had either undergone total hip replacement (THR) with a Birmingham resurfacing socket, the Durom resurfacing socket, or a Pinnacle metal-on-metal bearing surface. All patients recruited were at least one year following their surgery in order that their ion levels had reached a steady state. We reviewed every patient clinically, radiographically as well as biochemically. Blood was obtained for cobalt (Co) and chromium (Cr) levels. Current radiographs were arranged to assess the stability and mechanics of the total hip systems. All patients signed an informed consent and completed three questionnaires, The Western Ontario and McMaster Universities (WOMAC) index, the Short Form 36 (SF36) and UCLA activity score. A Harris Hip score was completed in order to assess individual hip function. Statistical analysis was performed on the collected data to assess whether there were any other potential influence on the mean levels of Co and Cr. Results. The blood metal ion levels in the larger non modular acetabular sockets were significantly raised compared to the Pinnacle group. For Co, 1.95 parts per billion (ppb) and 2.70 ppb in the Durom and Birmingham groups respectively compared to only 0.52 ppb in the Pinnacle group (P< 0.001). Cr levels were the same in the two monoblock systems, 1.9 ppb compared to the Pinnacle sockets 1.2 ppb (P<0.001). In all groups however these levels were within an acceptable safe range. The mean head size used in the Birmingham group was 53.2mm (Range 44mm to 56mm), and in the Durom group, 47.1 (Range 42 to 54mm). The mean head size used in the modular group was 37.3mm (Range 36–44mm). There was no difference between the three groups in terms of functional outcome and patient demographics were similar in all three groups. There was no statistical difference between the groups in terms of anteversion and abduction angles. There was also a smaller spread in this group in terms of range of angles. There was also no relationship between these values and the metal ion levels. Conclusion. All three total hip systems demonstrated average metal ion whole blood levels in a safe range. Larger diameter metal on metal bearings had higher ion levels

ARMD (Adverse Reaction to Metal Debris) is an increasingly recognised complication of metal on metal hip replacements. The MHRA (Medical and Healthcare Related Devices Agency) have advised a blood cobalt or chromium level above 7 mg/L is a threshold for further investigation, stating that “low levels are reassuring and strongly predict not having an adverse outcome”. Cross-sectional imaging should be performed when levels are above 7 mg/L. We have performed a study investigating the specificity and sensitivity of chromium and cobalt metal ion levels as a screening measure for ARMD. 79 ASR hip replacements were performed at our hospital and 75 (95%) of these underwent a Metal Artefact Reduction Sequence (MARS) MRI scan. All patients (64 hips) who had not undergone revision were invited to take part in this study. 57 patients with 62 hip replacements completed hip and activity scores, had blood cobalt and chromium ion level measurements and 3D-CT to measure acetabular component position. Acetabular component inclination (>50 degrees), small head size (< 51mm) and female gender were significantly correlated with raised chromium (Cr) and cobalt (Co) ion levels. An ARMD was detected using MRI in 18 (29%) of the hips in this study. The incidence of ARMD was significantly higher when chromium concentration was above 7 mg/l (p = 0.02). Chromium ion levels >7 mg/L had a sensitivity of 56% and specificity of 83% for ARMD, and cobalt ion levels >7 mg/L 56% and 76% respectively. 40 patients had cobalt levels <7 mg/L and 33 had chromium levels <7 mg/L, but 8 of these had an ARMD on MRI. All 8 patients had minimal symptoms (Oxford Hip Score ≥ 44 out of 48). The Medicines and Healthcare Products Regulatory Agency (MHRA) has recommended that cobalt and chromium levels be measured in patients with a metal-on-metal hip replacement and cross-sectional imaging performed when these levels are above 7 μg/L. This study has shown that by using this threshold, in patients with this implant combination, the sensitivity and specificity for the detection of ARMD is low and patients with soft tissue disease may be missed. Furthermore the presence of MRI detected ARMD, in the absence of significant clinical symptoms and with metal ion levels <7 μg/L is of concern. MoM implants at risk of failure are associated with raised cobalt and chromium levels. However metal ion analysis alone is not reliable as a screening tool for ARMD, which is often clinically “silent”. We recommend the routine use of MARS MRI as the safest method of ARMD diagnosis in patients with MoM implants

Introduction. Higher concentrations of metal ion levels after Metal-on-metal (MoM) THA are a cause for concern. Elevated cobalt (Co) and chromium (Cr) ion levels in the blood indicate metal wear, and may predict secondary soft-tissue damage (adverse reaction to metal debris; ARMD). Although, it is well known that concentrations of metal ion levels are elevated in the short term after MoM, the long-term consequences in ion concentration and risk factors for increased ion levels are not clarified. We sequentially investigated the postoperative Co and Cr ion levels after MoM THA and the relationship between the metal ion levels and several risk factors. Materials and Methods. We reviewed the data on one hundred and eighty six patients of two hundred ninety one MoM THA cases. The one hundred eighty six patients were measured at least three times after a MoM THA surgery over a five year (2005–2010) period in our institution. Serum cobalt and chromium levels were measured by inductor coupled plasma – mass spectrometry at several times in follow-up period, (measured at the preoperative period, the third month, the sixth month, the first year, the second year, and the fourth year after MoM THA). Furthermore, we investigated the correlation between the metal ion levels and various factors which might influence the release of metal ions, such as Body mass index (BMI), renal function, femoral head size, unilateral or bilateral THA, the cup position, and postoperative activity. The renal function was evaluated by measuring estimated glomerular filtration ratio (GFR) at preoperative examination. A postoperative activity was assessed with a pedometer measurement counting number of steps a day. A cup position was evaluated by lateral inclination measured by X-ray or computed tomography. Results. Average serum Co and Cr concentrations in preoperative period were 0.69 and 0.05 mg/ ml, respectively. Postoperative serum Co and Cr ion levels were significantly increased compared with preoperative value throughout the postoperative period. There was no significant correlation with regards to BMI, renal function, femoral head size tothe metal ion level measurement. In bilateral THA cases, Co and Cr ion concentrations were significantly increased compared with unilateral THA cases. In addition, in cases that its cup inclination was more than 50 degrees, Co and Cr ion concentration were significantly increased compared with cases less than 50 degrees in the first year after surgery. There was a trend for higher metal ion levels in the group of patients who walked more than 7000 steps a day, but this did not reach statistical significance. Conclusion. Metal ion concentrations of almost patients were increased after MoM THA surgery. Side effects related to elevation of serum Co or Cr concentration were currently not identified and overall clinical results were good. However, Longer follow-up would be necessary if the patients have overlapping risk factors, because those patients may experience elevation of the level in postoperative late stage

Introduction. Tribological studies have described a characteristic wear pattern of metal-on-metal hip resurfacings (MoMHRAs) with a run-in period followed by a ‘bedding-in’ phase minimising wear or by an increasing wear patch with edge loading. The use of metal ions as surrogate markers of in-vivo wear is now recommended as a screening tool for the performance of MoMHRAs. The aims of this retrospective, single-surgeon study were to measure ion levels in unilateral MoMHRAs at different stages during the steady-state in order to study the evolution of wear and factors affecting it. Methods. 218 consecutive patients with minimum two serum ion measurements were included. The mean age at surgery was 52.3 years, the first assessment was made at a mean of 2.5 years (11 months–8 years) and the last assessment at a mean of 4.6 years post resurfacing (2– 12 years). Ion level change was defined as Ion level at last assessment minus Ion level at first assessment. Ten different resurfacing designs were implanted, the majority being BHR (n=104), Conserve plus(n=55) and ASR (n=25). The median femoral component size was 50 mm (38–59mm). Radiological assessment of acetabular component orientation was made with EBRA. Results. For the whole cohort a significant reduction in Chromium (Cr) levels between initial [2.6 μg/ml (SD: 6.8)] and last assessment [1.9 μg/ml (SD: 8.3)] was found (p= 0.004). Cobalt (Co) levels were similar at initial [1.7 (SD: 7.7)] and last [1.8 (SD: 10.6)] follow-up (p=0.78). Cr levels increased in 31% and Co increased in 46% of patients. There was a significant ion level increase in 5% of patients. There was no significant difference between genders (p= 0.4) or implant designs (p = 0.07), but a trend of higher ions at last follow up with the ASR implants in comparison to BHR and C+. Neither component size (p=0.4) nor acetabular orientation (p=0.46) correlated with change in ion levels. However, a CPR distance (contact patch-rim) of <10mm was associated with an increase in Cr levels over time (p= 0.042). Patients with increasing ion levels had significantly lower Harris Hip Scores (p=0.038). Discussion. The analysis of the evolution of ion levels in unilateral hip resurfacing after the run-in phase demonstrates an overall decrease of Cr levels but no significant change in Co levels. This in vivo finding is consistent with tribocorrosion studies showing the formation of a passive protective film on the articulating surfaces after the initial wear-in, preventing further corrosion. From that point on, provided there is no edge loading causing increased surface wear, ions are mainly formed by corrosion of the particulate debris generated during the run-in phase. In vitro studies have shown a higher dissolution of the more soluble Co from the debris while Cr remains in solid form with less ion formation. In a number of cases in our study, ion levels continued to increase, indicating ongoing surface wear. These increasing ion levels were correlated with a lower coverage angle more prone to edge loading and with the development of clinical symptoms

INTRODUCTION. Metal-on-metal hip resurfacing arthroplasty (MoMHRA) is a surgical option in the treatment of end-stage hip disease. The measurement of systemic levels of metal ions gives an insight into the wear occurring and is advocated by regulatory bodies as routine practice in the assessment of resurfaced hips. However, the acceptable upper levels of Chromium (Cr) and Cobalt (Co) ions concentration with clinical significance still have to be established. The aim of this study is to address this issue in unilateral and bilateral resurfaced hips. METHODS. 453 patients with unilateral MoMHRA and 139 patients with bilateral MoMHRA at >12 months postoperative were retrospectively identified from an independent hip specialist's database. Routine metal ion levels were measured at last follow-up (ICPMS protocol). Radiological assessment included measurement of acetabular component orientation using EBRA, calculation of contact patch to rim (CPR) distance, and evaluation for any adverse X-ray findings. The cohort was divided into the well functioning group (Group A) and the non-well functioning group (Group B). A well functioning resurfacing gad to fulfil all of the following criteria (bilateral patients had to fulfil criteria for both hips): no patient reported hip complaints, no surgeon detected clinical findings, HHS> 95, CPR distance> 10mm, no abnormal radiological findings and no further operation scheduled. Upper levels (acceptable limits) of Cr/Co were considered to be represented by the top margin of the box-whisker plot [upper limit = 75. th. quartile value + (1.5 x interquartile range)] in Group A. RESULTS. 251 unilateral MoMHRAs patients (55%) and 58 patients with bilateral MoMHRAs (42%) comprised Group A. The majority of males were in Group A compared to the majority of females who belonged in Group B (p<0.001); subsequently Group A patients had bigger size components (p<0.001). Unilateral Group A [Cr: 2.0 µg/l (SD: 1.5)/ Co: 1.8µg/l (SD: 1.2)] patients had significantly lower ions than Group B [Cr: 7.3µg/l (SD: 17.3)/ Co: 6.6µg/l (SD: 18.1)] patients (p <0.001). Similarly, Group A bilateral patients [Cr: 3.8µg/l (SD: 2.7)/ Co: 2.8µg/l (SD: 1.9)] had significantly lower ions that Group B [Cr: 10.7µg/l (SD: 16)/ Co: 8.5µg/l (SD: 15.8)]. The upper levels (safe were: Cr: 4.6µg/l / Co: 4.0µg/l for unilateral MoMHRAs and Cr: 7.4µg/l / Co: 5.0µg/l for bilateral MoMHRAs. Unilateral MoMHRAs had significantly higher ion levels compared to bilateral patients (p <0.001). Sensitivity and specificity of these upper levels in predicting poor function were respectively 25% and 95% for Cr and 22% and 96% for Co. DISCUSSION. The findings of this study suggest that both unilaterally and bilaterally resurfaced patients with well functioning implants have low metal ion levels with upper levels of Cr: 4.6µg/l / Co: 4.0µg/l for unilateral MoMHRAs and Cr: 7.4µg/l / Co: 5.0µg/l for bilateral MoMHRAs These results indicate that the upper acceptable limit of metal ion levels in resurfaced hips is lower than the previously MHRA recommended threshold, however the study was conducted with very low tolerance for what was considered a clinically problematic hip. Well-functioning bilateral resurfacing have higher ion levels compared to well-functioning unilateral resurfacing