Metal Ion Levels in Total Hip Arthroplasty Versus Hip Resurfacing

Recent studies suggest that the tapered interface between stem and femoral head may be a substantial source of cobalt and chromium ion release after metal-on-metal (MOM) total hip arthroplasty (THA). This study compared patient ion levels after MOM hip resurfacing (HR) and MOM THA performed with identical acetabular components. 110 HRs were compared with 22 THAs. All had well-oriented components, unilateral implants, and serum ion studies beyond one year post-operatively. The HR group’s median cobalt value was 1.11 μg/L vs. 2.86 μg/L for the THA patients. The HR group’s median chromium value was 1.49 μg/L vs. 2.94 μg/L for THA. Significantly higher THA ion levels suggest a source of ions other than the MOM bearing itself.     

Serum metal ion concentrations after unilateral vs bilateral large-head metal-on-metal primary total hip arthroplasty

It is unknown if the presence of bilateral well-functioning large-head metal-on-metal (MOM) total hip arthroplasties (THAs) leads to higher serum metal ion concentrations than unilateral MOM THA. Elevated levels (chromium, 17 μg/L; cobalt, 19 μg/L) have been associated with poorly functioning MOM THA with metallosis. Fourteen patients having undergone bilateral and 25 patients having undergone unilateral large-head primary MOM THA were compared. Harris Hip Scores, University of California Los Angeles activity scores, radiographs, serum creatinine, and serum cobalt and chromium levels were obtained. Only cobalt ion levels were significantly higher in the bilateral group than in the unilateral group (1.8 μg/L vs 1.0 μg/L, P = .029). Comparatively, this magnitude is clinically rather low because ion levels did not approach those associated with metallosis in either group. We conclude that although patients with well-functioning bilateral MOM THA may have slightly higher cobalt levels, neither cobalt nor chromium levels approach those seen in poorly functioning MOM THA with metallosis.     

Exposure to chromium, cobalt and molybdenum from metal-on-metal total hip replacement and hip resurfacing arthroplasty

BACKGROUND: All metal implants--and metal-on-metal bearings in particular--corrode and cause a release of metal ions. Because cobalt and chromium have been shown to be carcinogenic and mutagenic in human and animal models, systemic toxicity and cancer risk are considered to be possible disadvantages of the metal-on-metal articulation. This study was designed to investigate the serum concentration profiles of chromium, cobalt and molybdenum after implantation of a Birmingham hip resurfacing arthroplasty (BHR) and a cementless total hip replacement with a 28-mm Metasul articulation (MTHR), over the first 2 years after implantation. METHODS: We analyzed profiles of metal ion serum levels in 111 patients implanted with a BHR, in 74 patients implanted with an MTHR, and in 130 implant-free probands control subjects using atomic absorption spectrophotometry. RESULTS: Chromium and cobalt concentrations (in microg/L) of all BHR and MTHR patients differed significantly from those of control subjects (chromium: < 0.25; cobalt: 0.25). The median chromium and cobalt concentrations in BHR patients had increased to 5.1 and 4.3 microg/L 2 years after surgery. Concentrations in BHR patient exceeded those in the unilateral MTHR patients. Molybdenum serum concentrations hardly changed over time in either group and were not significantly different from the concentrations seen in the control subjects. INTERPRETATION: During the first 2 years after surgery, the Birmingham hip resurfacing arthroplasty leads to a significantly greater increase in serum chromium and cobalt levels than the 28-mm metal-on-metal MTHR. Observation of patients over a longer period will be necessary in order to evaluate any chronic adverse effects to the system due to elevated chromium and cobalt serum concentrations.     

Current in vivo wear of metal-on-metal bearings assessed by exercise-related rise in plasma cobalt level.

Baseline metal ion levels are elevated in patients with metal-on-metal (MOM) hip arthroplasty. Interpretation of baseline levels is difficult as measurements are influenced by wear, corrosion, and metal ion release from stored metal in the body. Schmalzried et al. demonstrated that "wear is the function of use, not time." The specific research question we asked was: Does physiological exercise increase the wear of metal-on-metal articulation which can be measured from the plasma metal ion levels? Patients with three different well functioning MOM bearings [two types of resurfacing (BHR 46.8 mm and Cormet 48 mm) and Metasul 28 mm] were included. Blood samples were taken immediately before, immediately after, and 1 h after exercise to determine cobalt and chromium levels. A significant increase (p<0.005) in serum cobalt and chromium of 13% and 11%, respectively, was noticed after the exercise. Rise of cobalt levels in patients with a resurfacing MOM was 8.5 times (BHR group) or 6.5 times (Cormet group) larger than in those with a Metasul MOM (p=0.021 and p=0.047). Neither rise of metal levels nor baseline levels correlated with any other factor (p>0.27). Exercise-related elevations of plasma cobalt level provides information on current in vivo wear production that cannot be inferred from a baseline measurement of cobalt levels. Chromium levels cannot provide reliable information on the in vivo wear of the devices. Diameter was the important feature of the implant in determining exercise-related elevations of plasma cobalt level. Exercise-related elevations of plasma cobalt level is a potential in vivo tool to understand and improve the tribology of metal-metal bearings.     

The effect of the diameter of metal-on-metal bearings on systemic exposure to cobalt and chromium

The recent resurgence in the use of metal-on-metal bearings has led to fresh concerns over metal wear and elevated systemic levels of metal ions. In order to establish if bearing diameter influences the release of metal ions, we compared the whole blood levels of cobalt and chromium (at one year) and the urinary cobalt and chromium output (at one to three and four to six years) following either a 50 mm or 54 mm Birmingham hip resurfacing or a 28 mm Metasul total hip replacement. The whole blood concentrations and daily output of cobalt and chromium in these time periods for both bearings were in the same range and without significant difference.     

Exposure to chromium,cobalt and molybdenum from metal-on-metal total hip replacement and hip resurfacing arthroplasty

Background?All metal implants—and metal-on-metal bearings in particular—corrode and cause a release of metal ions. Because cobalt and chromium have been shown to be carcinogenic and mutagenic in human and animal models, systemic toxicity and cancer risk are considered to be possible disadvantages of the metal-on-metal articulation.

This study was designed to investigate the serum concentration profiles of chromium, cobalt and molybdenum after implantation of a Birmingham hip resurfacing arthroplasty (BHR) and a cementless total hip replacement with a 28-mm Metasul articulation (MTHR), over the first 2 years after implantation.

Methods?We analyzed profiles of metal ion serum levels in 111 patients implanted with a BHR, in 74 patients implanted with an MTHR, and in 130 implant-free probands control subjects using atomic absorption spectrophotometry.

Results?Chromium and cobalt concentrations (in μg/L) of all BHR and MTHR patients differed significantly from those of control subjects (chromium: < 0.25; cobalt: 0.25). The median chromium and cobalt concentrations in BHR patients had increased to 5.1 and 4.3 μg/ L 2 years after surgery. Concentrations in BHR patient exceeded those in the unilateral MTHR patients. Molybdenum serum concentrations hardly changed over time in either group and were not significantly different from the concentrations seen in the control subjects.

Interpretation?During the first 2 years after surgery, the Birmingham hip resurfacing arthroplasty leads to a significantly greater increase in serum chromium and cobalt levels than the 28-mm metal-on-metal MTHR. Observation of patients over a longer period will be necessary in order to evaluate any chronic adverse effects to the system due to elevated chromium and cobalt serum concentrations.     

Metal ion levels decrease after revision for metallosis arising from large-diameter metal-on-metal hip arthroplasty

Concerns have been renewed regarding the possible long-term effects of elevated circulating levels of cobalt and chromium as a direct result of implantation of large femoral head diameter metal-on-metal bearings. In order to establish whether metal ion levels remain persistently elevated, we compared metal ion levels before and after revision surgery in patients with large head diameter (greater than 38 mm) metal-on-metal total hip arthroplasty or hip resurfacing arthroplasty. At greater than one year post removal of a large-diameter metal-on-metal hip implant for the indication of symptomatic metallosis, metal ion levels were found to fall to almost normal levels.     

Levels of Cr,Co, Ni and Mo in Erythrocytes,Serum and Urine after Hip Resurfacing Arthroplasty

Background : Hip resurfacing arthroplasty is known to increase the metal ion concentration in the serum, urine and whole blood, with potentially adverse effects on the organism. However, only few data are available about the metal ion concentrations in erythrocytes, although they are directly exposed to the higher concentrations of the serum. Methods : The ion levels of chromium, cobalt, nickel and molybdenum in erythrocytes of 25 patients with a hip resurfacing implant were analysed with high resolution ICP-sf-MS (inductively-coupled-plasma-sector-field-mass-spectrometry). The results were compared to the ion levels in the serum and urine of the patients, and also to the ion levels of 27 control persons without an implant.

Results : Compared to the control group, ion levels in the erythrocytes of the hip resurfacing group were markedly increased for cobalt (0.10 vs. 3.26 μg/kg) and slightly for chromium (6.04 vs. 7.38 μg/kg). In contrast, ion levels in the serum of the hip resurfacing group were increased for cobalt (0.21 vs. 1.92 μg/l), chromium (1.48 vs. 5.64 μg/l), nickel (1.53 vs. 4.25 μg/l) and molybdenum (2.17 vs. 3.78 μg/l).

Conclusion : Ion concentrations of cobalt and chromium are also increased in erythrocytes after hip resurfacing arthroplasty. Further research is required to evaluate the impact of the elevated ion levels on the erythrocytes, and to evaluate if metal ions also accumulate in other tissues of the body.     

Serum metal ion levels after second-generation metal-on-metal total hip arthroplasty

Introduction  

Metal-on-metal bearings for total hip arthroplasty are increasing in popularity. However, metal ion toxicity, metal hypersensitivity, and metal carcinogenicity are the causes concern for patients with metal-on-metal hip replacement. We investigated serum levels of cobalt and chromium ions in patients with successfully implanted second-generation metal-on-metal total hip arthroplasty (THA) using PINNACLE-A (DePuy, Warsaw, IN, USA).     

Metal ion interpretation in resurfacing versus conventional hip arthroplasty and in whole blood versus serum. How should we interpret metal ion data

Metal ions generated from joint replacements are a cause for concern. There is no consensus on the best surrogate measure of metal ion exposure, and both serum and whole blood measurements are used in clinical practice. This study provides a guideline for interpretation of metal ion analysis in clinical practice. In a prospective trial comparing hip resurfacing (HR) with a conventional metal-on-metal (MoM) total hip arthroplasty (THA) cobalt and chromium levels were determined for whole blood and serum in 343 paired samples at regular intervals up to 24 months postoperatively. Cobalt whole blood and serum levels increased significantly after both procedures. Cobalt concentrations were significantly higher for the HR group compared to the THA group, at 3, 6 and 12 months, for whole blood and serum. At 24 months cobalt levels decreased and differences between HR and THA were no longer significant. In contrast, chromium whole blood levels remained significantly higher for HR until 24 months. Whole blood and serum levels could not be used interchangeably. The mean differences for cobalt and chromium between blood and serum values were +0.13 μg/L and -0.91 μg/L respectively. Regression analysis provided a formula for conversion from serum to blood of 0.34+[0.88*Co serum] for cobalt and 0.14 + [0.58*Cr serum] for chromium, with an acceptable prediction error below ±1.0 μg/L. Cobalt and chromium levels were significantly higher for HR versus THA, especially during the run-in phase of one year. Overall, the metal ion levels were well below 5 μg/L. We cannot recommend the use of whole blood over serum measurements or vice versa. The provided conversion formula between whole blood and serum in combination with the presented practical guidelines may be useful for clinical practice.     

Hip resurfacing versus metal-on-metal total hip arthroplasty - are metal ion levels different?

A systematic review and meta-analysis of trials comparing hip resurfacing to metal-on-metal total hip arthroplasty was conducted to determine if there is a difference in serum metal ion levels in patients receiving these implants. EMBASE and MEDLINE databases were searched from inception to December 2010 for all trials involving the use of these devices. Eligibility for inclusion in the review were studies with 1. comparative trials that were both retrospective and prospective; 2. inclusion of a treatment arm receiving hip resurfacing; 3. inclusion of a treatment arm receiving metal-on-metal total hip arthroplasty; and 4. analysis of chromium and cobalt ions, or either, in patient serum or whole blood at a minimum of 1 year after implantation. The literature search identified 87 potential studies, of which 10 met the inclusion criteria. Pooled mean differences were calculated for serum cobalt and chromium ion levels. Mean differences for serum cobalt and chromium metal ions were not significantly different between hip resurfacing and metal-on-metal total hip arthroplasty patients, although there was a tendency for lower serum cobalt ion levels in patients receiving hip resurfacing. Larger prospective randomized trials are required to better substantiate a difference in metal ion levels occurring between these implants.     

Metal ion levels after metal-on-metal Ring total hip replacement: a 30-year follow-up study

Metal-on-metal bearings for total hip replacement (THR) are becoming increasingly popular. Improved wear characteristics mean that these articulations are being inserted into younger patients in the form of THR and resurfacing procedures. This has led to concerns regarding potential carcinogenicity because of the increased exposure to metal ions that the procedure brings. We have studied the serum cobalt and chromium concentrations in patients who had primary, well-fixed Ring metal-on-metal THRs for more than 30 years. The levels of cobalt and chromium were elevated by five and three times, respectively compared with those in our reference groups. Metal-on-metal articulations appear to be the source of metal ions throughout the life of the prosthesis. In three patients who had undergone revision of a previous metal-on-metal THR to a metal-on-polyethylene replacement the levels of metal ions were within the normal range. The elevations of cobalt and chromium ions seen in our study were comparable with those in patients with modern metal-on-metal THRs.     

A prospective metal ion study of large-head metal-on-metal bearing: a matched-pair analysis of hip resurfacing versus total hip replacement

The current study measured ion release among large-head metal-on-metal hip bearings. Twenty-six patients with a modular, Profemur? TL with A-Class? big femoral head total hip replacement were matched (gender, femoral size, BMI) with a group of 26 patients with the Conserve? Plus implant hip resurfacing. Compared with HR patients, THR patients had higher median serum cobalt ion levels at 6 months (3.26 vs 1.12 μg/L, P = .002) 1 year (4.51 vs 1.02, P = .002), and 2 years (3.77 vs 1.22, P<.001) following surgery. No differences in chromium ions were observed. Further research is required to determine the clinical significance of elevated serum cobalt ions.     

Revision of hip resurfacing arthroplasty

Metal-on-metal (MOM) hip resurfacing has become an increasingly popular treatment for young, active patients with degenerative disease of the hip, as bearing surfaces with better wear properties are now available. One proposed advantage of resurfacing is its ability to be successfully revised to total hip arthroplasty (THA). In addition, radiographic parameters that may predict failure in hip resurfacing have yet to be clearly defined. Seven MOM resurfacing arthroplasties were converted to conventional THAs because of aseptic failure. Using Harris Hip Scores (HHS) and Short Form 12 (SF-12) questionnaire scores, we compared the clinical outcomes of these patients with those of patients who underwent uncomplicated MOM hip resurfacing. In addition, all revisions were radiographically evaluated. Mean follow-up periods were 51 months (revision group) and 43 months (control group). There was no significant difference between the 2 groups' HHS or SF-12 scores. There was no dislocation or aseptic loosening after conversion of any resurfacing arthroplasty. Valgus neck-shaft angle (P < .03) was associated with aseptic failure of MOM hip resurfacing. Conversion of aseptic failure of hip resurfacing to conventional THA leads to clinical outcomes similar to those of patients who undergo uncomplicated hip resurfacing. The orientation of the femur and the components placed play a large role in implant survival in hip resurfacing. More work needs to be done to further elucidate these radiographic parameters.     

Chinese experience with metal-on-metal hip resurfacing

The aim of this study was to study the actual clinical and laboratory results of metal-on-metal resurfacing hip arthroplasties by comparing with other implants. A total of 127 cases were operated on at the Department of Orthopaedics of Wuhan Union Hospital from 2005 to 2011. An important cause of failure is the fracture of the femoral neck. The chromium and cobalt levels of resurfacing hip arthroplasty and large-diameter head total hip arthroplasty (THA) are higher than those of a conventional metal-on-polyethylene total hip arthroplasty. There was a high ion level associated with an abduction angle of more than 45° and repetitive extreme hip motion in the 3 revision cases. The findings of this study are novel and quite controversial with that of the previously published literature.     

Serum cobalt and serum chromium level in 2 patients with chronic renal failure after total hip prosthesis implantation with metal-metal gliding contact

PURPOSE: The influence of chronic renal failure on serum cobalt and serum chromium in two patients with metal-on-metal bearing (Metasul) and cementless total hip arthroplasty (Alloclassic) is investigated. METHODS: Serum cobalt and serum chronium levels were determined in the postoperative course using atomic absorption spectrometry. RESULTS: Maximum values are found to be more than 100-fold elevated when compared to the reported median serum cobalt concentrations in patients with the same prosthesis type and no known renal disease. CONCLUSION: Chronic renal failure seems to be responsible for the marked elevation of serum cobalt and serum chromium. CLINICAL RELEVANCE: Despite evidence of adverse health reactions, a possible effect of long-term cobalt and chromium loading cannot be neglected. In our opinion, metal-on-metal bearings in THA should not be inserted in patients with chronic renal failure. Follow-up investigations (serum cobalt, serum chromium, serum creatinine, BUN, echocardiography) should be performed at short intervals.     

Breast Milk Metal Ion Levels in a Young and Active Patient With a Metal-On-Metal Hip Prosthesis

Metal-on-metal resurfacing arthroplasty of the hip has been used increasingly over the last 10 years in younger active patients. The dissolution of the metal wear particles results in measurable increases in cobalt and chromium ions in the serum and urine of patients with a metal-on-metal bearing. We measured the cobalt, chromium, and molybdenum ion levels in urine; serum; and breast milk in a young and active patient with a metal-on-metal hip prosthesis after a pathologic fracture of the femoral neck. Metal-on-metal hip prosthesis leads to increasing levels of molybdenum in breast milk in the short-term follow-up. There are no increasing levels of chromium and cobalt ions in breast milk. Besides the already known elevated concentrations in serum of chromium and cobalt after implantation of a metal-on-metal hip prosthesis, we found no increasing levels of chromium and cobalt in urine.