Blood Metal Ion Research Articles

Long-Term Results of a Second-Generation, Small-Diameter, Metal-On-Metal Bearing in Primary Total Hip Arthroplasty at 14-year Follow-Up.

(1) Background: The objective of the present study was to review the clinical and radiological results of a small-head, MoM bearing in primary THA and to determine blood metal ion levels at long-term follow-up. (2) Methods: We retrospectively evaluated the clinical and radiological results of 284 small-diameter, MoM 28-mm Metasul THA at a mean follow-up of 14.5 years, and measured blood metal ion concentrations in 174 of these patients. (3) Results: After 14 years, survival free for revision due to any reason was 94%. Proximal femoral osteolysis was seen in 23% of hips, and MRI demonstrated ARMD in 27 of the 66 investigated hips (41%). Mean cobalt, chromium, and titanium ion concentrations were 0.82 µg/L (range 0.22–4.45), 1.51 µg/L (0.04–22.69), and 2.68 µg/L (0.26–19.56) in patients with unilateral THA, and 2.59 µg/L (0.43–24.75), 2.50 µg/L (0.26–16.75), and 3.76 µg/L (0.67–19.77), respectively in patients with bilateral THA. Twenty-nine percent of patients showed cobalt or chromium ion levels > 2 µg/L. (4) Conclusions: Despite good clinical long-term results, increased blood metal ion levels (cobalt or chromium > 2 µg/L) were found in approximately one-third of asymptomatic patients, and proximal femoral osteolysis and ARMD were frequently seen in this cohort. Blood metal ion analysis appears helpful in the long-term follow-up of these patients in order to identify individuals at risk. In accordance with contemporary consensus statements, symptomatic patients with elevated metal ion levels and/or progressive osteolysis should be considered for additional CT or MARS MRI to determine the extent of soft tissue affection prior to revision surgery. Further studies are necessary to investigate the clinical relevance of ARMD in asymptomatic patients with small-head, MoM THA.

How to Interpret Metal Ions in THA

BackgroundModern total hip arthroplasty has seen an unfortunate increase in proportional implant failures secondary to adverse local tissue reactions (ALTRs) secondary to wear of metal-on-metal (MoM) bearings and mechanically assisted crevice corrosion (MACC) related to corrosion at implant junctions and tapers. The purpose of this study is to describe the appropriate choice of metal ion testing and evaluation of those levels to identify failed total hip arthroplasty implants containing cobalt and chromium. MethodsWhen presented with an arthroplasty of concern, the surgeon must determine what metal ion levels to obtain and then incorporate those levels into a treatment algorithm. Patients with painful hip arthroplasties are evaluated for chromium and cobalt by obtaining whole blood and synovial metal levels. ResultsSynovial fluid cobalt had the highest correlation with ALTR compared with the other tests, with a threshold of 19.75 ng/ml, with a specificity of 89%, if the cobalt-to-chromium ratio is greater than 1.4 ng/ml in a metal on polyethylene hip, with a sensitivity of 95%. ConclusionThe interpretation of whole blood metal ions is a key component of the algorithm in treating the symptomatic hip arthroplasty but is not to be used in a vacuum.

Current evidence from a worldwide, multicentre, follow-up study of the recalled Articular Surface Replacement Hip System.

Our first aim was to report the longitudinal clinical performance of patients treated with the ASR Hip System, a metal-on-metal (MoM) device, in their mid- to late-term follow-up. Secondly, we sought to report on the reasons and risk factors for mid- to late-term implant failure. A total of 1721 ASR patients (1933 hips) from 16 centres in 6 countries were enrolled to a prospective, post-recall study. The average time to enrollment was 7.4 years from index surgery. Data from 3 follow-up visits over 2 years were analysed. Implant performance, based on ion levels and PROMs, was determined at each clinical visit. The proportion of those exhibiting good performance decreased over time for hip resurfacing (ASR HRA) and total hip arthroplasty (ASR XL) patients. ASR XL patients were likely to exhibit longitudinal blood metal ion increases regardless of symptom state. ASR HRA patients were more likely to present with and maintain good performance over time, especially males with high general health indicators. 6% of ASR HRA and 14% of ASR XL patients were revised throughout the study period. ASR XL THA patients are likely to exhibit blood metal ion increases without accompanying changes in symptom state, and therefore should be followed with annual blood tests at minimum. While appropriately selected ASR HRA patients were the most likely to exhibit low blood metal ion levels and report no symptoms, we recommend vigilant follow-up of all ASR patients to ensure that worsening clinical outcomes and asymptomatic soft tissue damage are not missed.

Local Biological Reactions and Pseudotumor-Like Tissue Formation in relation to Metal Wear in a Murine In Vivo Model.

Metal wear debris and released ions (CoCrMo), which are widely generated in metal-on-metal bearings of hip implants, are also found in patients with metal-on-polyethylene bearings due to the mechanically assisted crevice corrosion of modular taper junctions, including head-neck and neck-stem taper interfaces. The resulting adverse reactions to metal debris and metal ions frequently lead to early arthroplasty revision surgery. National guidelines have since been published where the blood metal ion concentration of patients must consistently be monitored after joint replacement to prevent serious complications from developing after surgery. However, to date, the effect of metal particles and metal ions on local biological reactions is complex and still not understood in detail; the present study sought to elucidate the complex mechanism of metal wear-associated inflammation reactions. The knee joints in 4 groups each consisting of 10 female BALB/c mice received injections with cobalt chrome ions, cobalt chrome particles, and ultra-high-molecular-weight polyethylene (UHMWPE) particles or PBS (control). Seven days after injection, the synovial microcirculation and knee joint diameter were assessed via intravital fluorescence microscopy followed by histological evaluation of the synovial layer. Enlarged knee diameter, enhanced leukocyte to endothelial cell interactions, and an increase in functional capillary density within cobalt chrome particle-treated animals were significantly greater than those in the other treatment groups. Subsequently, pseudotumor-like tissue formations were observed only in the synovial tissue layer of the cobalt chrome particle-treated animals. Therefore, these findings strongly suggest that the cobalt chrome particles and not metal ions are the cause for in vivo postsurgery implantation inflammation.

Has the threshold for revision surgery for adverse reactions to metal debris changed in metal-on-metal hip arthroplasty patients? A cohort study of 239 patients using an adapted risk-stratification algorithm

Background and purpose — A risk-stratification algorithm for metal-on-metal hip arthroplasty (MoMHA) patients was devised by US experts to help clinicians make management decisions. However, the proposed algorithm did not cover all potential patient or surgical abnormalities. Therefore we adapted the US risk-stratification algorithm in MoMHA patients revised for adverse reactions to metal debris (ARMD) to determine the variability in the revision threshold, and also whether high-risk patients had inferior outcomes following revision.Patients and methods — We analysed 239 MoMHA revisions for ARMD between 2001 and 2016 from 2 centres with pre-revision blood metal ions and imaging. Patients were stratified (low risk, moderate risk, high risk) using pre-revision factors (implant, radiographic, blood metal ions, cross-sectional imaging) by adapting a published algorithm. The risk categories for each factor were assessed against revision year, revision centre, and post-revision outcomes (re-revision surgery, and any poor outcome).Results — Compared with hips revised before 2012, hips revised from 2012 onwards included more high-risk implants (44% vs. 17% pre-2012), high-risk radiographic features (85% vs. 69% pre-2012), and low-risk metal ions (41% vs. 19% pre-2012). 1 centre more frequently revised patients with high-risk implants (48% vs. 14%) and low-risk blood metal ions (45% vs. 15%) compared with the other. All these comparisons were statistically significant (p < 0.05). With the limited sample size available, implant, radiographic, blood metal ion, and cross-sectional imaging risk groups did not statistically significantly affect the rates of re-revision surgery or frequency of poor outcomes post-revision.Interpretation — When applying the adapted risk-stratification algorithm the threshold for ARMD revision changed over time, presumably due to increasing evidence, patient surveillance, and investigation since 2012. Lower blood metal ion thresholds were used from 2012 for ARMD revisions; however, there was evidence that centres attached different importance to metal ions when managing patients. High-risk patients did not have inferior outcomes following ARMD revision.

Does modularity of metal-on-metal hip implants increase cobalt: chromium ratio?

Blood metal ion levels are used in the surveillance of metal-on-metal (MoM) hip implants. Modular implants contain an extra source of metal debris that may affect the ratio of metal ions in the blood. This was a retrospective study of 503 patients with hip replacements made by a single manufacturer (Smith & Nephew, Warwick, UK) with the same bearing surface. There were 54 total hip arthroplasties, 35 Birmingham Mid-Head Resections and 414 hip resurfacings. Whole blood metal ion levels and their ratios were analysed to investigate the effect of a modular junction. The cobalt:chromium ratios were greater in the total hip arthroplasty group (mean 2.3:1) when compared to the resurfacings group (mean 1.3:1, p = <0.05) and Birmingham Mid-Head Resection group (mean 1.1:1, p = 0.11). This study demonstrated a trend for a higher cobalt:chromium ratio in patients with MoM total hip replacement that may be due to metal debris from the modular stem-head junction. Further work is required to correlate clinical data with retrieval analysis to confirm the effect of taper material loss on the cobalt:chromium ratio.

Blood metal levels, leucocyte profiles, and cytokine profiles in patients with a modular dual-mobility hip prosthesis: early results from a prospective cohort study.

The aim of this study was to evaluate blood metal ion levels, leucocyte profiles, and serum cytokines in patients with a total hip arthroplasty (THA) involving modular dual-mobility components. A total of 39 patients were recruited, with clinical follow-up of up to two years. Outcome was assessed using the Harris Hip Score (HHS, the 12-Item Short-Form Health Survey (SF-12), the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and a visual analogue scale (VAS) for pain. Blood concentrations of cobalt (Co), chromium (Cr), and serum cytokines were measured. Subpopulations of leucocytes were analyzed by flow cytometry. The clinical performance was good. Blood Co levels (ref 1.0 µg/l) were mildly elevated in seven patients at three months, and two patients at two years' follow-up. The preoperative Cr levels were normal except for one patient with a detectable Cr (1.2 µg/l). Cr levels were detectable in three patients at three months, two patients at one year, and three patients at two years' follow-up. No patients had symptoms suggestive of failure. Although flow cytometry showed constant circulating leucocyte profiles, there was a significant reduction of serum interleukin (IL)-4, IL-5, and interferon gamma (IFNγ) postoperatively compared with the preoperative levels (p < 0.05). These results suggest that THA using modular dual-mobility components is safe. This allows an opportunity to use a large femoral head and a thick polyethylene bearing surface, which is especially useful in revision procedures or high-risk situations when added stability is required. Cite this article: Bone Joint J 2019;101-B:1035-1041.

Early Results of Our International, Multicenter, Multisurgeon, Double-Blinded, Prospective, Randomized, Controlled Trial Comparing Metal-on-Metal With Ceramic-on-Metal in Total Hip Arthroplasty

BackgroundThe aim of our prospective, multicenter, randomized, controlled trial (titled M2A-38 Ceramic-on-Metal RCT, NCT00754520) is to demonstrate noninferiority of a ceramic-on-metal (CoM) articulation compared with metal-on-metal (MoM) in total hip arthroplasty. The study arms are at 8 years since implantation, with metal ion and functional score analysis at 5 years. MethodsWe recruited 211 patients between 2009 and 2011. The patients were randomized to ceramic or metal. A cohort of these patients had whole blood metal ions performed yearly, and all patients underwent annual radiographic and clinical outcome assessment. All revisions were recorded and some explants were analyzed. Recruitment ceased earlier than planned owing to concerns raised with failure of MoM implants. ResultsNo significant difference was seen in patient demographics, radiographic parameters, or functional outcomes at any time point. Lower cobalt ion levels were seen in the CoM group (P < .01) at all time points. Chromium levels were significantly lower in the CoM group up to 3 years, but raised at 5 years. There were slightly fewer revisions for adverse reaction to metal debris in the CoM group. Explant analysis suggested a different wear pattern to those seen in the MoM group. ConclusionThe results demonstrated that the CoM articulation behaved the same as the MoM in terms of functional outcome and radiographic parameters. The CoM coupling also demonstrates raised metal ions beyond 3 years and increasing revisions for adverse reaction to metal debris. It remains difficult to see a clinical application for CoM and further exploration or use is not warranted.

Response profiles of circulating leukocytes and metal ions in patients with a modular dual-mobility hip implant.

The purpose of this study was to retrospectively evaluate blood metal ion levels and leukocyte profiles in patients with modular dual-mobility hip implant (MDM) during a postoperative follow-up up to 2 years. We recruited 49 patients in a retrospective cohort study and had postoperative follow-up up to 2 years. Blood concentrations of chromium (Cr), cobalt (Co) and serum cytokines were measured. Flow cytometry was used to quantify the subpopulations of leukocytes, including CD14+ and CD16+ monocytes, CD3+ T lymphocytes, CD19+ B lymphocytes, CD4+ Helper T-cells and CD45+RA memory vs. naïve T-cells. Clinical performances of implants were good during 2 years of follow-up. Cr levels were normal in all patients and only detectable in 1 patient (1.4µg/L, ref < 5.0µg/L). Co levels were mildly elevated in 4 patients at 1 year (mean 1.375µg/L, range 1.2-1.7µg/L, ref < 1.0µg/L) and in 2 patients at 2-year follow-up (both 1.2µg/L). Interestingly, Co level observed in 3 patients at 1 year converted to undetectable at their 2-year follow-up. Percentages of B cells, T cells and their subpopulations were within normal levels. There was no increase of CD16+ inflammatory monocytes. With the recent introduction of MDM systems there is potential for metal ion release from the interface between the acetabular shell and CoCr liner. Clinical results have been good and metal levels undetectable or within acceptable ranges at 1-2 years. There was no evidence of activated immune response, as manifested by constant circulating leukocyte profiles and no increase of CD16+ inflammatory monocytes.

Changing the Blood Test: Accurate Determination of Mercury(II) in One Microliter of Blood Using Oriented ZnO Nanobelt Array Film Solution-Gated Transistor Chips.

The measurement of ultralow concentrations of heavy metal ions (HMIs) in blood is challenging. A new strategy for the determination of mercury ions (Hg2+ ) based on an oriented ZnO nanobelt (ZnO-NB) film solution-gated field-effect transistor (FET) chip is adopted. The FET chips are fabricated with ZnO-NB film channels with different orientations utilizing the Langmuir-Blodgett (L-B) assembly technique. The combined simulation and I-V behavior results show that the nanodevice with ZnO-NBs parallel to the channel has exceptional performance. The sensing capability of the oriented ZnO-NB film FET chips corresponds to an ultralow minimum detectable level (MDL) of 100 × 10-12 m in deionized water due to the change in the electrical double layer (EDL) arising from the synergism of the field-induced effect and the specific binding of Hg2+ to the thiol groups (-SH) on the film surface. Moreover, the prepared FET chips present excellent selectivity toward Hg2+ , excellent repeatability, and a rapid response time (less than 1 s) for various Hg2+ concentrations. The sensing performance corresponds to a low MDL of 10 × 10-9 m in real samples of a drop of blood.

Ultrasensitive sensor based on novel bismuth carbon nanomaterial for lead and cadmium determination in natural water, contaminated soil and human plasma

Abstract Heavy metals are ubiquitous in the environment, and their excessive discharge and bioaccumulation can cause cardio-vascular and urinary diseases in humans. Among them, lead ion (Pb2+) and cadmium ions (Cd2+) are designated as the most typical toxic metal ions in human blood and drinking water. Thus, high-performance monitoring of Pb2+and Cd2+ pollution is necessary. Nanomaterials have been extensively used in electrochemical sensing due to their excellent physicochemical properties. In this study, we prepared ordered mesoporous carbon doped hollow spherical bismuth oxide nanocomposites (hsBi2O3-OMC NCs), and constructed it into an electrochemical sensor for highly sensitive and specific detection of Pb2+ and Cd2+ in environmental media and human blood based on the differential pulse anodic stripping voltammetry (DPASV). The experimental results demonstrate that the detection range could be broadened to 200 nM with detection limits of 0.025 nM for Pb2+ and 0.045 nM for Cd2+. Compared with conventional detection techniques, this sensor exhibited simple operation, minimal background interference, multipath applicability and economic efficiency. Therefore, we believe that this work is significant for pollution monitoring, environmental restoration and emergency treatment.

Repeated cobalt and chromium ion measurements in patients with large-diameter head metal-on-metal ReCap-M2A-Magnum total hip replacement

Background and purpose — Whole blood (WB) cobalt (Co) and chromium (Cr) ion levels have a major role in the follow-up of metal-on-metal total hip replacement (MoM THR). We investigated, first, if there was a change in WB Co or Cr levels over repeated measurements in patients with ReCap-M2A-Magnum THR, and, second, determined how many patients had WB Co or Cr levels that exceeded the safe upper limits (SUL) in the repeated whole blood metal ion assessment.Patients and methods — A Recap-M2A-Magnum THR was used in 1,329 operations (1,188 patients) at our institution between 2005 and 2012. We identified all patients (n = 319) with unilateral ReCap-M2A-Magnum implants who had undergone at least 2 repeated metal ion measurements with the first blood sample taken mean 5.5 years (1.8–9.3) after surgery and the second taken mean 2 years (0.5–3) after the first.Results — The median WB Co and Cr ion levels decreased in repeated measurements from 1.40 (0.40–63) ppb to 1.10 (0.20–68) ppb and from 1.60 (0.60–13.0) ppb to 1.10 (0.30–19.0) ppb, respectively. 7% of the Co ion values exceeded SUL at the initial measurement, and 7% at the control measurement. The proportion of Cr ion values exceeding the safe upper limit (SUL) decreased during the measurement interval from 5% to 4%.Interpretation — Repeated metal ion measurements in unilateral ReCap-M2A-Magnum patients in a mean 2-year time interval did not show any increase. Long-term ion levels are, however, not yet known.

The Outcome of Revision Surgery for Failed Metal-on-Metal Total Hip Arthroplasty

BackgroundMetal-on-metal total hip arthroplasties (MoM THAs) are frequently revised, though there is a paucity of functional outcome data. We report on outcomes and prognostic factors predictive of outcome from the largest series of MoM THA revisions to date. MethodsA single-center consecutive series of revisions from MoM THAs was identified. The cohort was divided by the presence or absence of symptoms prior to revision. The primary outcome was functional outcome (Oxford Hip Score [OHS]). Secondary outcomes were complication data, pre-revision and post-revision blood metal ions, and modified Oxford classification of pre-revision magnetic resonance imaging. ResultsOne hundred eighty revisions at median follow-up of 5.48 years were identified. Median OHS improved from 29 to 37 with revision (P < .001). Symptomatic patients experienced the greatest functional benefit (ΔOHS 6.5 vs 1.4, P = .012), while the function of asymptomatic patients was unaffected by revision (P = .4). Use of a cobalt-chromium-containing bearing surface at revision and increased body mass index were predictive of poor functional outcome. ConclusionSymptomatic patients experience greater functional benefit from revision surgery but do not regain the same level of function as patients who were asymptomatic prior to revision. Body mass index and use of cobalt-chromium-containing bearing surfaces are prognostic for poor functional outcome.

Is a modular dual mobility acetabulum a viable option for the young, active total hip arthroplasty patient?

Modular dual mobility (DM) prostheses in which a cobalt-chromium liner is inserted into a titanium acetabular shell ( vs a monoblock acetabular component) have the advantage of allowing supplementary screw fixation, but the potential for corrosion between the liner and acetabulum has raised concerns. While DM prostheses have shown improved stability in patients deemed 'high-risk' for dislocation undergoing total hip arthroplasty (THA), their performance in young, active patients has not been reported. This study's purpose was to assess clinical outcomes, metal ion levels, and periprosthetic femoral bone mineral density (BMD) in young, active patients receiving a modular DM acetabulum and recently introduced titanium, proximally coated, tapered femoral stem design. This was a prospective study of patients between 18 and 65 years of age, with a body mass index (BMI) < 35 kg/m2 and University of California at Los Angeles (UCLA) activity score > 6, who received a modular cobalt-chromium acetabular liner, highly crosslinked polyethylene mobile bearing, and cementless titanium femoral stem for their primary THA. Patients with a history of renal disease and metal hardware elsewhere in the body were excluded. A total of 43 patients (30 male, 13 female; mean age 52.6 years (sd 6.5)) were enrolled. All patients had a minimum of two years' clinical follow-up. Patient-reported outcome measures, whole blood metal ion levels (ug/l), and periprosthetic femoral BMD were measured at baseline, as well as at one and two years postoperatively. Power analysis indicated 40 patients necessary to demonstrate a five-fold increase in cobalt levels from baseline (alpha = 0.05, beta = 0.80). A mixed model with repeated measures was used for statistical analysis. Mean Harris Hip Scores improved from 54.1 (sd 20.5) to 91.2 (sd 10.8) at two years postoperatively (p < 0.001). All patients had radiologically well-fixed components, no patients experienced any instability, and no patients required any further intervention. Mean cobalt levels increased from 0.065 ug/l (sd 0.03) preoperatively to 0.30 ug/l (sd 0.51) at one year postoperatively (p = 0.01) but decreased at two years postoperatively to 0.16 ug/l (sd 0.23; p = 0.2). Four patients (9.3%) had a cobalt level outside the reference range (0.03 ug/l to 0.29 ug/l) at two years postoperatively, with values from 0.32 ug/l to 0.94 ug/l. The mean femoral BMD ratio was maintained in Gruen zones 2 to 7 at both one and two years postoperatively using this stem design. At two years postoperatively, mean BMD in the medial calcar was 101.5% of the baseline value. Use of a modular DM prosthesis and cementless, tapered femoral stem has shown encouraging results in young, active patients undergoing primary THA. Elevation in mean cobalt levels and the presence of four patients outside the reference range at two years postoperatively demonstrates the necessity of continued surveillance in this cohort. Cite this article: Bone Joint J 2019;101-B:365-371.

Obesity is not associated with hip failure in patients with articular surface replacement of the hip.

Our main aim was to investigate whether obese patients were at increased risk of elevated metal ion levels and/or adverse local tissue reaction (ALTR) after being treated with articular surface replacement (ASR) hip arthroplasty. This study included 360 patients who underwent metal-on-metal (MoM) hip resurfacing (HRA) or total hip arthroplasty (THA). 95 patients (26%) were underweight/normal weight (BMI < 25 kg/m2), 139 (39%) were overweight (BMI 25-30 kg/m2), and 126 (36%) were obese (BMI ⩾ 30 kg/m2). Blood metal ion levels and patient-reported outcome measures (PROMs) were obtained, and a sub-cohort of 85 patients had MARS MRI performed. Logistic regression analyses were used to assess the associations between obesity and metal ions, as well as ALTR. BMI was not associated with either elevated metal ion levels or ALTR. In HRA patients, female gender (OR 3.0; p = 0.019) and pain (OR 2.3; p = 0.046) were associated with elevated Co levels. Female patients had increased risk of elevated Cr levels (OR 3.0; p = 0.02). In THA patients, female gender (OR 2.2; p = 0.004) and VAS satisfaction (OR 2.1; p = 0.01) were associated with elevated Co levels. Female gender (OR 3.6; p = 0.001) and time from surgery (OR 1.4; p = 0.005) were associated with Cr levels. In the sub-cohort, ALTR was associated with Co levels (OR 16.1; p = 0.002) in HRA patients. Patients with BMI ⩾ 30 kg/m2 present no increased risk for elevated metal ion levels or development of ALTR.

10-year results of ReCap hip resurfacing arthroplasty: a non-designer case series

We present the 10-year results of the ReCap Magnum HRA system in a consecutive single surgeon's series from a non-designer centre. Hip resurfacing arthroplasty (HRA) was performed in active males under 65 years and in pre-menopausal females with adequate bone density proven by a DEXA scan. Clinical follow-up; annual Oxford hip scoring, UCLA scoring and whole blood metal ion level measurement. Kaplan-Meier method was used to determine survivorship with revision as the end point. Radiographs were analysed for; acetabular inclination, notching, neck thinning and change in implant position. 72 HRAs were performed in 66 patients with a mean age of 45.7 years. The mean follow-up was 10.63 ± 0.54 years (range 10-11.75 years). The survivorship of the cohort at minimum 10 years was 97.22% (95% confidence interval 94.14-99.01). There was a significant improvement in the Oxford Hip Score from 15.77 ± 4.33 to 45.67 ± 4.43 (p < 0.001) and the UCLA score from 3.14 ± 0.74 to 7.07 ± 1.16 (p < 0.001). Mean whole blood cobalt and chromium levels were 28.83 ± 8.42 nmol/l and 39.93 ± 9.64 nmol/l respectively. There were 2 revisions, due to avascular necrosis and implant failure. In our series the implant has performed well with <1% failure per year. We did not note any difference between the genders, since all the females in our series had been screened for osteopenia using a DEXA scan. All our patients returned to an active lifestyle which was maintained at final follow-up. Strict selection criteria and a well-designed implant result in good long-term functional and radiological results with hip resurfacing.

Concordance between laboratories in metal ion testing in patients with metal-on-metal hip implants.

Testing of whole blood or serum metal ion levels has become an important part of assessing and monitoring the performance of metal-on-metal bearings, both in hip resurfacing arthroplasty and in total hip replacement. The aim of this study was to determine the concordance between 2 laboratories testing cobalt and chromium ion levels in patients with metal-on-metal bearings. Serum and whole blood samples from patients who had undergone metal-on-metal resurfacing or large-diameter total hip arthroplasty were tested for cobalt and chromium ions in laboratory A (a recognized laboratory) and laboratory B (tasked with testing clinical specimens). Laboratory A performed cobalt and chromium testing on whole blood, and laboratory B performed cobalt testing on whole blood and chromium testing on serum. Samples from 104 patients were tested. Laboratory B reported lower whole blood cobalt levels than laboratory A. Furthermore, laboratory A reported that all patients had elevated whole blood cobalt ion levels compared to the normal reference values for the laboratory, whereas laboratory B reported that 46 patients (44.2%) had whole blood cobalt ion levels within the normal reference range for the laboratory. This comparative study highlights the importance of using a single laboratory for metal ion testing, as values generated from different laboratories may not be directly comparable. With recent literature suggesting that whole blood cobalt levels as low as 1 ppb may be a predictor of adverse reactions to metal debris, accurate clinical measurement needs to be increasingly exact.

Follow-up of Metal-on-Metal Hip Replacements at a Large District Hospital and the Implementation of Medicines and Healthcare Products Regulatory Agency Guidelines: A Review of 297 Patients.

BackgroundMedicines and Healthcare products Regulatory Agency (MHRA) guidance for patients with metal-on-metal (MoM) hip replacements was provided in 2012 and updated in 2017 to assist in the early detection of soft-tissue reactions due to metal wear debris. A large number of MoM hip replacements were undertaken at our hospital trust. A program of recall for all patients with MoM hip replacements was undertaken and MHRA guidelines were implemented. In this study, we aimed to investigate the effectiveness of the revised MHRA guidelines in the detection of early adverse reactions to metal debris and to re-evaluate the indications for metal artifact reduction sequence magnetic resonance imaging (MARS-MRI) and revision surgery.MethodsIdentification and recall of all patients with MoM hip replacements from 2001 were conducted by using theatre logs, patient records, clinical coding information, and consultant logbooks. Two senior arthroplasty consultants reviewed X-rays and patient records. Postal questionnaires were forwarded to patients, together with requests for general practitioners to complete cobalt and chromium blood tests. The two consultant-led review of MOM replacements was undertaken with further radiological investigations (X-rays, MARS-MRI) performed according to the 2017 guidance with support of consultant radiologists.ResultsOf 674 identified patients, 297 were available for review: 26 patients did not have MoM implants, 36 were untraceable, 59 refused follow-up, 87 moved out of area, 147 had died, and 22 already had revision. Of 297 patients, 126 were women and 171 were men; age range was 39 to 95 years (mean age, 69 years); 126 had resurfacing and 171 had MoM replacements. Twenty-six patients had elevated metal ions. Thirty-three patients underwent MARS-MRI: MARS-MRI results were positive in 17 and negative in 16. Of 17 patients with positive MARS-MRI, 10 patients were asymptomatic and seven were waiting revision.ConclusionsPositive MARS-MRI can often occur in the absence of elevated metal ion levels; elevated blood metal ion levels do not mean MARS-MRI will be positive. All patients with MoM replacements were at risk. It is imperative to assess patients regularly for symptoms that may raise clinical suspicion and maintain a low threshold to performing MARS-MRI.

In vivo blood metal ion levels in patients after total shoulder arthroplasty

Products from metal wear have been identified as a potential cause of adverse local tissue reactions and implant failure in total hip arthroplasty. However, the role of metal ion exposure in patients after total shoulder replacement is unclear. The objective of the present study was to determine in vivo blood metal ion levels of cobalt, chromium, and titanium in patients after anatomic total shoulder arthroplasty (TSA) or reverse TSA. A consecutive series of patients after anatomic TSA or reverse TSA was evaluated retrospectively. After exclusion of patients with additional metal implants, 40 patients with unilateral anatomic TSA (n = 20) or reverse TSA (n = 20) were available for whole-blood metal ion analysis at a mean follow-up of 28 ± 9.6 months. Twenty-three healthy individuals without metal implants served as a control group. Mean cobalt ion concentrations were 0.18 µg/L (range, 0.1-0.66 µg/L), 0.15 µg/L (range, 0.03-0.48 µg/L), and 0.11 µg/L (range, 0.03-0.19 µg/L), mean chromium ion levels were 0.48 µg/L (range, 0.17-2.41 µg/L), 0.31 µg/L (range, 0.09-1.26 µg/L), and 0.14 µg/L (range, 0.04-0.99 µg/L), and mean titanium ion concentrations were 1.31 µg/L (range, 0.75-4.52 µg/L), 0.84 µg/L (range, 0.1-1.64 µg/L), and 0.62 µg/L (range, 0.32-2.14 µg/L) in the reverse TSA group, the anatomic TSA group, and the control group, respectively. TSA resulted in elevated metal ion levels compared with healthy controls, although overall metal ion concentrations measured in this study were relatively low. The role of local metal ion exposure in patients with total shoulder replacements should be further investigated.

Retrieval Findings of Recalled Dual-Taper Hips.

Background:The recent high-profile recalls of several dual-taper hip designs pose questions regarding why those designs perform poorly. We aimed to characterize taper damage in 1 recalled design to understand failure mechanisms to inform surgeons on which patients should be considered at risk of revision and when to revise.Methods:High-precision measurement equipment was used to characterize the metal loss from the neck-stem interface of 116 retrieved Rejuvenate femoral stems (Stryker Howmedica Osteonics) revised because of an adverse reaction to metal debris. Head-neck taper surfaces were also investigated, and clinical and laboratory data were examined.Results:The neck-stem junction of each implant was moderately to severely corroded and showed a characteristic wear pattern on both male and female taper surfaces. The severity of taper damage was positively correlated with time to revision (coefficient, 0.040 [95% confidence interval (CI), 0.028 to 0.051]; p < 0.0001) and with serum cobalt concentration (coefficient, 0.02 [95% CI, 0.01 to 0.02]; p < 0.0001) and serum chromium concentration (coefficient, 0.04 [95% CI, 0.009 to 0.070]; p = 0.0142).Conclusions:A forensic examination of the retrieved components that failed secondary to an adverse reaction to metal debris showed, in all cases, visible corrosion. Of the implant and patient factors investigated, we did not identify any predictors of corrosion. The severity of damage was found to increase with time; cobalt was significantly elevated over chromium.Clinical Relevance:Surgeons should scrupulously follow and consider revision for patients with this implant design to avoid extensive tissue excision. Blood metal ion tests may aid in identifying the mechanisms of taper corrosion.