Cobalt and chromium levels in blood and urine following hip resurfacing arthroplasty with the Conserve Plus implant

Is end-organ surveillance necessary in patients with well-functioning metal-on-metal hip resurfacings?

Aims

Cardiac magnetic resonance (CMR) was used to assess whether cardiac function or tissue composition was affected in patients with well-functioning metal-on-metal hip resurfacing arthroplasties (MoMHRA) when compared with a group of controls, and to assess if metal ion levels correlated with any of the functional or structural parameters studied.

Patients and Methods

In all, 30 participants with no significant cardiac history were enrolled: 20 patients with well-functioning MoMHRA at mean follow-up of 8.3 years post-procedure (ten unilateral, ten bilateral; 17 men, three women) and a case-matched control group of ten non-MoM total hip arthroplasty patients (six men, four women). The mean age of the whole cohort (study group and controls) at the time of surgery was 50.6 years (41.0 to 64.0). Serum levels of cobalt and chromium were measured, and all patients underwent CMR imaging, including cine, T2* measurements, T1 and T2 mapping, late gadolinium enhancement, and strain measurements.

Results

None of the MoMHRA patients showed clinically significant cardiac functional abnormality. The MoMHRA patients had larger indexed right and left end diastolic volumes (left ventricular (LV): 74 ml/m2 vs 67 ml/m2, p = 0.045; right ventricular: 80 ml/m2 vs 71 ml/m2, p = 0.02). There was a small decrease in T2 time in the MoMHRA patients (median 49 ms vs 54 ms; p = 0.0003). Higher metal ion levels were associated with larger LV volumes and with shorter T2 time.

Conclusion

Although cardiac function is not clinically adversely affected in patients with well-functioning MoMHRA, modern imaging is able to demonstrate subtle changes in structure and function of the heart. As these changes correlate with systemic ion measurements, they may be consequences of wear debris deposition. Longer, longitudinal studies are necessary to determine whether cardiac function will become affected. Cite this article: Bone Joint J 2019;101-B:540–546.

Metal on Metal Hip Resurfacing in Patients 45 Years of Age and Younger at Minimum 5-Year Follow-Up

BACKGROUND

Metal on metal hip resurfacing (MoM-HR) is an alternative to total hip arthroplasty in young and active patients. The purpose was to determine the survivorship of MoM-HR procedures performed in patients aged 45 years and younger assessing patient-reported outcome measures (PROMs) at minimum 5-year follow-up.

METHODS

All 217 patients equal to or younger than 45 years of age at the time of surgical intervention presenting to our center with MoM-HR between May 2002 and May 2011 were prospectively followed. Baseline demographic data, preoperative and postoperative radiographic measurements, and validated PROMs were obtained (Hip Disability and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, and University of California, Los Angeles Activity Score). Survivorship was calculated using Kaplan-Meier analysis, and risk factors for failure were identified using multivariate regression analysis.

RESULTS

The overall survivorship excluding septic failures was 94.6% and 93.8% at 5 and 10 years, respectively. Aseptic loosening of the acetabular component was the most common mode of failure (11/20 cases). Gender, head size, and acetabular abduction angle had no significant effect on survivorship. Significant improvements in PROMs were seen for Hip Disability and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, and University of California, Los Angeles Activity Scale (P < .001).

CONCLUSION

This study indicates that MoM-HR is a suitable option for young individuals, as demonstrated through improved functional scores and low revision rates. The survivorship of HR in the younger than 45 age-group was similar to that of total hip arthroplasty, as well as HR in older patients. Given the proposed benefits of HR, this procedure may be viewed as a viable option in patients aged younger than 45 years.

Correlation between serum metal ion levels and adverse local tissue reactions after Conserve® Plus hip resurfacing arthroplasty

BACKGROUND

Adverse local tissue reactions (ALTR) have been associated with the use of metal-on-metal (MoM) bearings and the monitoring of cobalt (Co) and chromium (Cr) ion levels in blood or serum may be the best way to evaluate in vivo the wear of these bearings. However, the relationship between Co and Cr ion concentrations and the formation of ALTR remains unclear.

METHODS

We investigated the relationship between ALTR and serum Co and Cr ion levels and identified the clinical factors influencing the formation of ALTR in patients treated with MoM hip resurfacing arthroplasties. 228 patients with unilateral Conserve® Plus MoM hip resurfacing had serum metal ion studies performed more than 1 year after surgery. Metal artifact reduction sequence magnetic resonance imaging (MARS MRI) was performed on subjects at risk for ALTR as determined by a screening protocol.

RESULTS

12 patients had ALTR. Logistic regression showed a strong association of ALTR with elevated ion levels and with low (<10 mm) contact patch to rim distance.

CONCLUSIONS

MoM bearings require enough functional coverage of the socket by design and then precise implantation to maximise functional coverage of the femoral ball, enhance lubrication, and avoid edge-loading wear.

What should I expect from my recalled Adept Hip Resurfacing?

"My Hip Resurfacing (HR) has been recalled. What will happen to me?" This is the question of every patient who underwent an implant recall, a highly stressful event for both patients and physicians. Triggered by a 11.64% failure rate at 7 years, a recall process started for Adept HR with head diameter less than 48 mm. We report our experience in the recall process of 40 patients with the above-mentioned components. One patient underwent revision surgery due to an adverse reaction to metal debris at 5-year follow-up. None of the patients were scheduled for revision, with an estimated survival rate of 97.6% at 7 years. Implants were well positioned with an average acetabular inclination angle of 37°. Cobalt and chromium blood levels were below the safety threshold of clinical relevance. Functional scores were excellent. In the case of a well-positioned device with normal ion levels, a good performance of the implant is generally observed. Even if we experienced a very low revision rate, this may certainly get worse over time since not all possible failures are predictable, thus requiring a careful periodic follow-up.

What Is the Natural History of Asymptomatic Pseudotumors in Metal-on-metal THAs at Mid-term Followup?

BACKGROUND

The risk of early revision because of pseudotumors in patients who have undergone large-head metal-on-metal (MoM) total hip arthroplasty (THA) is well documented. However, the natural history of asymptomatic pseudotumors or of MoM articulations without pseudotumors is less well understood. The aim of our study was to investigate the natural history of primary MoM THA at mid-term followup.

QUESTIONS/PURPOSES

The purposes of this study were: (1) Did previously detected pseudotumors persist or worsen in asymptomatic patients at mid-term followup; and if so, did any of them require revision THA? (2) Did new pseudotumors form in asymptomatic patients at mid-term followup? (3) What happened to serum trace metal ions at mid-term followup? (4) Were postoperative patient-reported outcome measures (PROMs) maintained at mid-term followup?

METHODS

Seventy-one patients who underwent a MoM THA using a Metasul LDH implant with a Durom acetabular cup and an M/L Taper stem between September 2005 and October 2008 were reviewed. All patients for this study were part of two previously published studies from our early followup. Data from the previous studies were used for comparison only. Two of the 71 patients (2.8%) were lost to followup. The mean age at operation was 56 years (range, 34-68 years). There were 24 female patients. All patients had serum trace metal ions testing, ultrasound imaging, and PROMs at a mean 3.5 years (early followup) after the index operation (range, 3-5 years) and delayed followup at a mean 7 years (range, 6.5-9 years). The indication to undertake revision THA was based on clinical evaluation and not solely on the investigation results.

RESULTS

Twenty-three of 71 patients (32%) had a positive ultrasound scan for pseudotumor at early followup. Of these, eight patients underwent revision THA (11% of MoM THA or 35% of patients with an early positive ultrasound scan). The mean time between positive ultrasound scan and revision surgery was 13 months (range, 5-22 months). Of the remaining 15 patients with pseudotumor noted on early ultrasound, 12 had persistent pseudotumor, two resolved, and one was lost to followup. Six patients (13%) with a normal ultrasound scan at early followup showed new ultrasound findings at delayed followup. Of these, four (8%) were conclusively diagnosed as pseudotumor and one was revised. Serum trace metal ion increased at mid-term followup in the seven cases that showed an increase in volume of pseudotumor. Of the five patients in whom the volume of pseudotumor decreased on ultrasound at mid-term followup, three showed a decrease in serum trace ions levels, whereas two showed an increase. New-onset pseudotumors at mid-term followup was associated with an increase in serum trace metal ions at mid-term followup only in two of six cases. PROMs at mid-term followup of patients in this study remain high.

CONCLUSIONS

At mid-term followup, approximately 35% of patients who develop an early pseudotumor undergo revision arthroplasty, whereas the remaining are asymptomatic. The incidence of new-onset ultrasound findings suggestive of pseudotumors at mid- to long-term followup is approximately 8% and these require continued surveillance.

LEVEL OF EVIDENCE

Level II, prognostic study.

High serum ion levels in Conserve Plus big femoral head cemented total hip arthroplasty

AIM

We report the short-term clinical, radiographic and ion level data of the Conserve Plus metal-on-metal (MoM) big femoral head (BFH) total hip arthroplasty (THA), used with a cemented cobalt-chrome (Co-Cr) Profemur Xm stem and a titanium (Ti) modular neck.

RESULTS

In a consecutive series of 40 hips, survivorship at 3 years was 92.5% with revision for any reason. Average Harris Hip Score was 91.3. There were no implant loosenings. No osteolysis was observed. 5 patients had signs of adverse local tissue reaction (ALTR); their clinical scores were not different from the whole cohort. All but 1 patient had their Co serum ion levels measured. The average Co level was 14,1 µg/l (range 0.9-29.0; median 13.0 µg/l). Clinical scores did not correlate with ion level data. A comparative group of 42 hip resurfacing arthroplasties from the same manufacturer had significantly lower serum Co levels: 1.51 µg/l (range 0.9-4.0; median 0.9 µg/l).

CONCLUSIONS

All patients with the MoM BFH THA design should be followed regularly and should have ion level testing.

Prevalence of Failure due to Adverse Reaction to Metal Debris in Modern, Medium and Large Diameter Metal-on-Metal Hip Replacements--The Effect of Novel Screening Methods: Systematic Review and Metaregression Analysis

Metal-on-metal (MoM) hip replacements were used for almost a decade before adverse reactions to metal debris (ARMD) were found to be a true clinical problem. Currently, there is a paucity of evidence regarding the usefulness of systematic screening for ARMD. We implemented a systematic review and meta-analysis to establish the prevalence of revision confirmed ARMD stratified by the use of different screening protocols in patients with MoM hip replacements. Five levels of screening were identified: no screening (level 0), targeted blood metal ion measurement and/or cross-sectional imaging (level 1), metal ion measurement without imaging (level 2), metal ion measurement with targeted imaging (level 3) and comprehensive screening (both metal ions and imaging for all; level 4). 122 studies meeting our eligibility criteria were included in analysis. These studies included 144 study arms: 100 study arms with hip resurfacings, 33 study arms with large-diameter MoM total hip replacements (THR), and 11 study arms with medium-diameter MoM THRs. For hip resurfacing, the lowest prevalence of ARMD was seen with level 0 screening (pooled prevalence 0.13%) and the highest with level 4 screening (pooled prevalace 9.49%). Pooled prevalence of ARMD with level 0 screening was 0.29% and with level 4 screening 21.3% in the large-diameter MoM THR group. In metaregression analysis of hip resurfacings, level 4 screening was superior with regard to prevalence of ARMD when compared with other levels. In the large diameter THR group level 4 screening was superior to screening 0,2 and 3. These outcomes were irrespective of follow-up time or study publication year. With hip resurfacings, routine cross-sectional imaging regardless of clinical findings is advisable. It is clear, however, that targeted metal ion measurement and/or imaging is not sufficient in the screening for ARMD in any implant concepts. However, economic aspects should be weighed when choosing the preferred screening level.

Toxicity and bioactivity of cobalt nanoparticles on the monocytes

OBJECTIVE

To explore the toxicity and biological activity of cobalt nanoparticles on the osteoclasts. Analyze the relationship between cobalt nanoparticles and osteolysis.

METHODS

Monocyte-macrophages (RAW 264.7) was cultured in vitro, osteoclast-like cells were induced by lipopolysaccharides (LPS). After RAW 264.7 was induced for 24 h, Methyl Thiazolium Tetrazolium (MTT) biological toxicity test of osteoclast-like cell was preceded using Cobalt nanoparticles (set 4 concentrations: 10, 20, 50, 100 μM) and cobalt chloride (set 4 concentrations: 10, 20, 50, 100 μM) at 2, 4, 8, 24 and 48 h respectively. The relative expression of mRNA of CA II and Cat K after RAW 264.7 induction was determined by Q-PCR.

RESULTS

mRNA relative expression of CA II, Cat K were reduced at multiple concentrations both cobalt nanoparticles and cobalt chloride, and was time and concentration dependent, cobalt nanoparticles are more significant than cobalt chloride group. But when the cobalt nanoparticles concentration is in 10-50 μM, the mRNA relative expression of CA II, Cat K increased.

CONCLUSION

Cobalt nanoparticles have biological toxicity. At multiple concentrations, the differentiation and proliferation of osteoclasts was inhibited, but when the concentration of cobalt nanoparticles is in 10-50 μM, it has been strengthened.

Excellent short-term results of hip resurfacing in a selected population of young patients

BACKGROUND

Hip resurfacing (HR) is an alternative option to total hip arthroplasty (THA) in a population of selected patients (young and/or active).

HYPOTHESIS

The short-term survivorship rate is as least as good as that for THA with no abnormal increase in serum metal ion levels.

MATERIALS AND METHODS

A continuous prospective series of 502 hip resurfacings in 481 patients mean age 48.7 years old (±10.3; 18-68) (Conserve Plus, Wright Medical Technology) was analyzed clinically, radiologically and biologically (total blood chrome, cobalt and titanium metal ion levels). Mean follow up was 4.1 years (1.9-4.9).

RESULTS

There were no dislocations. There were 5 cases of revision surgery with component replacement (including 2 infections). Implant survivorship using implant removal as the criteria (excluding infection) was 99.4% at 4 years (CI 95%: 98.1-99.8). The evaluation of metal ion levels showed a significant increase in cobalt from a preoperative level of 0.24 μg/L (0.01-3.6) to 0.86 μg/L (0.01-5.7) at the final follow-up (P<0.001). Chrome and titanium levels went from 0.68 μg/L (0.01-4.4) and 2.36 μg/L (0.39-7) to 1.28 μg/L (0.1-5.5) and 4.49 μg/L (1.29-8.21) respectively (P<0.001). All clinical scores had significantly improved at the final follow-up. Mean frontal plane cup inclination was 42.7° (35-62).

DISCUSSION

In a selected population of young and/or active patients, the short-term results of hip resurfacing are excellent. At the postoperative 4-year follow-up the rate of complications (in particular the absence of dislocations) was less than that for THA in young and/or active patients. Certain conditions must be respected to obtain these results; frontal plane cup inclination of between 40 and 45°, a femoral head diameter of at least 48 mm and good quality femoral bone.

LEVEL OF EVIDENCE

IV.

Serum Metal Ions with a Titanium Modular Neck Total Hip Replacement System

The goal of this study is to evaluate serum levels of chromium (Cr), cobalt (Co), and titanium (Ti) within the first two years following total hip arthroplasty using a Ti modular neck system. Twenty-five patients were randomized to a metal-on-metal (MoM) bearing with an all CoCr shell, and the remaining 25 received a metal-on-polyethylene (MoP) with a Ti shell. Serum levels demonstrated increases for Cr, Co, and Ti at 1 year (P < .001). MoM had similar Ti levels to MoP hips at 1 year (P=0.11) but lower at 2 years (P=0.03). Results suggest that the passive corrosion (i.e., chemical, pitting, and crevice corrosion) of exposed non-articular metal surfaces may be a greater source of ions than the neck-stem or head-neck interfaces.

Do hardened femoral heads reduce blood metal ion concentrations after hip resurfacing?

BACKGROUND

Elevated cobalt and chromium ion concentrations have been associated with the use of metal-on-metal bearings in hip arthroplasty. The use of a differential hardness bearing may reduce metal particle release. The aim of our study was to compare circulating cobalt (Co) and chromium (Cr) ion levels between patients treated with a standard all 'as-cast' heat treated bearing and a differential hardness bearing.

MATERIALS AND METHODS

One hundred and thirty-two patients implanted with unilateral hip resurfacing arthroplasties and having had blood metal ion studies performed between one and six years after surgery were retrospectively selected. There were 73 patients in the standard all 'as cast' heat treated bearing group (group 1) and 59 in the differential hardness bearing group (group 2).

RESULTS

Clinical and quality of life scores were comparable between groups. The median Co in group 1 was 1.01 µg/L and 1.23 µg/L in group 2 (p = 0.0566). The median Cr in group 1 was 1.60 µg/L and 1.34 µg/L in group 2 (p = 0.0505).

CONCLUSION

Compared with conventional heat-treated CoCr bearings, differential hardness metal-on metal bearings do not confirm in vivo the hopes of a substantial reduction in circulating metal ions concentrations suggested by in vitro wear studies.

Metal-on-metal hip surface replacement

Metal-on-metal resurfacing of the hip (MoMHR) has enjoyed a resurgence in the last decade, but is now again in question as a routine option for osteoarthritis of the hip. Proponents of hip resurfacing suggest that its survival is superior to that of conventional hip replacement (THR), and that hip resurfacing is less invasive, is easier to revise than THR, and provides superior functional outcomes. Our argument serves to illustrate that none of these proposed advantages have been realised and new and unanticipated serious complications, such as pseudotumors, have been associated with the procedure. As such, we feel that the routine use of MoMHR is not justified.

Cite this article: Bone Joint J 2014;96-B(11 Suppl A):17–21.

Five year results of the first US FDA-approved hip resurfacing device

A prospective, multi-center postmarket approval study has been ongoing since May 2006 to assess safety and efficacy of the first US FDA approved hip resurfacing implant. 265 patients have been enrolled at five study sites. The average age of the patients is 51.3 years. There have been 7 revisions (2.4%) in the cohort to date. K-M survival curves for the cohort are 97.6% at 5 years. There is a trend toward a gender difference in implant survivorship, with 98.6% of men and 94.7% of women free from revision. Metal ion analysis revealed median cobalt and chromium levels of 1.5 ppb and 1.7 ppb at 1 year. In this prospective US study, the Birmingham Hip Resurfacing implant is demonstrating results comparable to those in the literature.

Hip resurfacing versus total hip arthroplasty: a systematic review comparing standardized outcomes

BACKGROUND

Metal-on-metal hip resurfacing was developed for younger, active patients as an alternative to THA, but it remains controversial. Study heterogeneity, inconsistent outcome definitions, and unstandardized outcome measures challenge our ability to compare arthroplasty outcomes studies.

QUESTIONS/PURPOSES

We asked how early revisions or reoperations (within 5 years of surgery) and overall revisions, adverse events, and postoperative component malalignment compare among studies of metal-on-metal hip resurfacing with THA among patients with hip osteoarthritis. Secondarily, we compared the revision frequency identified in the systematic review with revisions reported in four major joint replacement registries.

METHODS

We conducted a systematic review of English language studies published after 1996. Adverse events of interest included rates of early failure, time to revision, revision, reoperation, dislocation, infection/sepsis, femoral neck fracture, mortality, and postoperative component alignment. Revision rates were compared with those from four national joint replacement registries. Results were reported as adverse event rates per 1000 person-years stratified by device market status (in use and discontinued). Comparisons between event rates of metal-on-metal hip resurfacing and THA are made using a quasilikelihood generalized linear model. We identified 7421 abstracts, screened and reviewed 384 full-text articles, and included 236. The most common study designs were prospective cohort studies (46.6%; n = 110) and retrospective studies (36%; n = 85). Few randomized controlled trials were included (7.2%; n = 17).

RESULTS

The average time to revision was 3.0 years for metal-on-metal hip resurfacing (95% CI, 2.95-3.1) versus 7.8 for THA (95% CI, 7.2-8.3). For all devices, revisions and reoperations were more frequent with metal-on-metal hip resurfacing than THA based on point estimates and CIs: 10.7 (95% CI, 10.1-11.3) versus 7.1 (95% CI, 6.7-7.6; p = 0.068), and 7.9 (95% CI, 5.4-11.3) versus 1.8 (95% CI, 1.3-2.2; p = 0.084) per 1000 person-years, respectively. This difference was consistent with three of four national joint replacement registries, but overall national joint replacement registries revision rates were lower than those reported in the literature. Dislocations were more frequent with THA than metal-on-metal hip resurfacing: 4.4 (95% CI, 4.2-4.6) versus 0.9 (95% CI, 0.6-1.2; p = 0.008) per 1000 person-years, respectively. Adverse event rates change when discontinued devices were included.

CONCLUSIONS

Revisions and reoperations are more frequent and occur earlier with metal-on-metal hip resurfacing, except when discontinued devices are removed from the analyses. Results from the literature may be misleading without consistent definitions, standardized outcome metrics, and accounting for device market status. This is important when clinicians are assessing and communicating patient risk and when selecting which device is most appropriate for individual patients.

Acetabular component thickness does not affect mid-term clinical results in hip resurfacing

BACKGROUND

The benefits of using thin acetabular components for hip resurfacing have been shown in terms of bone conservation, but there currently are little data available in the literature addressing the mid-term clinical results of these devices.

QUESTIONS/PURPOSES

We aimed to determine whether thinner acetabular components altered mid-term postoperative clinical scores, complication rates, survivorship, radiographic appearance, and metal ion levels.

METHODS

Two hundred eighty-one patients with unilateral disease received a 5-mm thick acetabular shell and 223 received a 3.5-mm shell. The femoral component implanted in both groups was identical. We compared clinical scores, complication rates, survivorship, radiographic results, and ion levels between these two groups.

RESULTS

UCLA hip scores were similar (pain, p = 0.0976; walking, p = 0.9571; function, p = 0.9316; activity, p = 0.2085). Complications were higher in the 5-mm group (6.4% versus 1.8%, p = 0.0431). Both groups were similar regarding survivorship (p = 0.3181), cup radiolucency at 5 years (p = 0.107), and metal ion levels (cobalt p = 0.404, chromium p = 0.250).

CONCLUSIONS

With comparable mid-term clinical results, there is no tangible reason to abstain from using the 3.5-mm acetabular component.

LEVEL OF EVIDENCE

Level III, retrospective comparative study. See the Guidelines for Authors for a complete description of levels of evidence.

Our midterm results of the Birmingham hip resurfacing with and without navigation

We reviewed 148 consecutive hip resurfacings in order to assess the clinical outcomes of the BHR at midterm follow-up and to compare the accuracy of the navigation in the positioning of femoral component. We retrospectively analyzed 85 hips using the conventional jig to implant the femoral component and we prospectively followed 63 hips operated on by navigation. At a mean follow-up of 50.54 months, the Harris hip score improved significantly from 44.66 preoperatively to 98.45 postoperatively without any differences between the groups. Radiologically, we classic navigated group. Our clinical outcomes are excellent at midterm follow-up and the navigation definitely improves the implant position in both planes.

The natural history of inflammatory pseudotumors in asymptomatic patients after metal-on-metal hip arthroplasty

BACKGROUND

Although pseudotumors have been reported in 32% of asymptomatic metal-on-metal hips, the natural history of asymptomatic pseudotumors is unknown.

QUESTIONS/PURPOSES

The purpose of this study was to assess changes over time in asymptomatic pseudotumors and the effect of revision on pseudotumor mass.

METHODS

Followup ultrasound was performed a mean of 25.8 months (range, 21-31 months) after the detection of 15 pseudotumors and five isolated fluid collections in a cohort of 20 asymptomatic patients (13 metal-on-metal, three metal-on-polyethylene, and four hip resurfacings) [42]. Changes in pseudotumors and fluid collections size and nature, and serum ion levels were determined.

RESULTS

Among the 15 nonrevised patients, pseudotumors increased in size in six (four solid and two cystic) of 10 patients, three of which had clinically important increases (13-148 cm(3); 28-74 cm(3); 47-104 cm(3)). Three pseudotumors (one solid and two cystic) disappeared completely (the largest measured 31 cm(3)). One solid pseudotumor decreased in size (24 to 18 cm(3)). In five revised patients, pseudotumors completely disappeared in four patients. The fifth patient had two masses that decreased from 437 cm(3) to 262 cm(3) and 43 cm(3) to 25 cm(3). All revision patients had a reduction of chromium (40.42 μ/L to 2.69 μ/L) and cobalt ions (54.19 μ/L to 0.64 μ/L). Of five isolated fluid collections, four completely disappeared (two metal-on-metal and two metal-on-polyethylene) and one (metal-on-metal) increased from 26 cm(3) to 136 cm(3).

CONCLUSIONS

Our observations suggest pseudotumors frequently increase in size in asymptomatic patients with occasional remission of small masses. Revision resulted in remission of pseudotumors.

Chromium and cobalt ion concentrations in blood and serum following various types of metal-on-metal hip arthroplasties: a literature overview

BACKGROUND AND PURPOSE

Widely different metal ion concentrations in blood and serum have been reported with metal-on-metal (MoM) implants. We reviewed the literature on blood and serum ion concentrations of chromium (Cr) and cobalt (Co) following various MoM hip arthroplasties.

METHODS

Studies were searched for in the Medline database, Embase, and the Cochrane Database of Systematic Reviews. Highest mean or median ion concentrations of Cr and Co after a minimum of 1 year of follow-up were extracted and grouped according to sample- and articulation type, and average values were calculated.

RESULTS

43 studies were included and 16 different MoM implants were identified. For the different types of bearings, average ion concentrations and range were calculated from the mean or median ion concentration. The average Cr concentration ranged between 0.5 and 2.5 μg/L in blood and between 0.8 and 5.1 μg/L in serum. For Co, the range was 0.7-3.4 μg/L in blood and 0.3-7.5 μg/L in serum.

INTERPRETATION

When the average blood ion concentrations calculated for the different implants, together with the concentrations measured in the individual studies, were compared with the upper acceptable limit for Cr and Co in blood, no clear pattern was recognized. Furthermore, we were unable to detect any clear difference in ion concentrations between different types of implants (THA and resurfacing).

MR imaging of metal-on-metal hip prostheses

Metal-on-metal (MoM) hip arthroplasty was expected to provide benefits over metal-on-polyethylene systems. After widespread placement of MoM implants, outcomes have been disappointing. MoM implants are associated with higher serum levels of metal ions, adverse periarticular soft tissue reactions, and increased long-term failure rates. In light of these findings, it is crucial that patients with MoM implants be closely monitored for adverse effects. MR imaging is ideally suited for assessment of these patients and complements standard clinical evaluation and laboratory testing. This article reviews the background of MoM implants, emerging data on complications, strategies for using MR imaging, and MR imaging findings in patients with reaction to metal.

Contact patch to rim distance predicts metal ion levels in hip resurfacing

BACKGROUND

Component design, size, acetabular orientation, patient gender, and activity level have been suggested as factors leading to elevated metal ion concentrations after-on-metal hip resurfacing arthroplasty (MMHRA). The calculation of the contact patch to rim (CPR) distance integrates component size, design, and acetabular orientation and may be a good predictor of elevated metal ion levels.

QUESTIONS/PURPOSES

We evaluated the effects and the predictive value of the CPR distance on serum cobalt (CoS) and chromium (CrS) ion levels.

METHODS

We retrospectively studied 182 patients with Conserve Plus MMHRAs at a minimum of 12 months after surgery (median, 57 months; range, 12-165 months). CoS and CrS levels were analyzed using inductively-coupled plasma mass spectrometry. Multiple logistic regression was performed to determine which if any of the factors related to serum ion levels.

RESULTS

Patients with CPR distances of 10 mm or less had a 37-fold increased risk of having elevated CoS of 7 μg/L or higher. Similarly, these patients had an 11-fold increased risk of having elevated CrS of 7 μg/L or higher. Sex and University of California Los Angeles activity scores did not influence the postoperative CoS and CrS levels. The negative predictive value for CPR distance less than 10 mm was 99.3% for CoS greater than 7 μg/L and 98.0% for CrS greater than 7 μg/L.

CONCLUSIONS

Our observations suggest the CPR distance would be a useful indicator to determine which patients are at risk for elevated ion levels. Patients with CPR distances greater than 10 mm need not be monitored unless they become symptomatic.

Toll-like receptor 4 signaling pathway mediates proinflammatory immune response to cobalt-alloy particles

Metal orthopedic implant debris-induced osteolysis of hip bone is a major problem in patients with prosthetic-hips. Although macrophages are the principal targets for implant-wear debris, the receptor(s) and mechanisms underlying these responses are not fully elucidated. We examined whether the TLR4 pathway mediates immune response to metal-on-metal (MoM) implant-generated wear particles. Human monocytes (THP-1) were exposed to Co-alloy particles at increasing particle:cell ratio for 24 h. Challenge with particles caused up-regulation of IL-1β, TNF-α and IL-8, and mediated degradation of cytosolic I-κB and nuclear translocation of NF-κB. Blocking antibodies against TLR4 or gene silencing of MyD88 and IRAK-1 prevented particle-induced I-κB/NF-κB activation response and markedly inhibited IL-8 release. Particle-mediated IL-8 response was not observed in TLR4-negative HEK293T cells; whereas transfection-based TLR4-overexpression in HEK293T enabled particle-sensitivity, as observed by I-κB degradation and IL-8 expression in response to particles. Results demonstrate that Co-alloy particles trigger immune response via the TLR4-MyD88-dependent signaling pathway.

Case report: High chromium and cobalt levels in a pregnant patient with bilateral metal-on-metal hip arthroplasties

BACKGROUND

Metal-on-metal bearings frequently are used in young patients leading to the concern that disseminated metals such as chromium (Cr) and cobalt (Co) as the main constituents could affect pregnancies.

CASE DESCRIPTION

We describe a 41-year-old patient with bilateral metal-on-metal hip arthroplasties, a recurrent pseudotumor, and extremely high blood levels (Cr 39 μg/L, Co 138 μg/L) at 12 gestational weeks. At different gestational weeks, maternal blood, aspirate of the pseudotumor, and amniotic fluid were analyzed for Cr and Co. Therapy with chelating agents was not recommended because the mother showed no symptoms of toxicity and the safety of chelating therapy during pregnancy is not established. At 38 weeks of gestation, a healthy male infant was delivered with elevated Cr and Co cord blood levels. At the age of 8 weeks, the infant's Cr was comparable to the cord blood level, whereas the Co decreased considerably without treatment. At the age of 14 weeks, the infant's development was seemingly uneventful and no signs of toxicity were obvious.

LITERATURE REVIEW

Carcinogenic, mutagenic, and teratogenic potentials of these metals have been suggested. However, we found no published clinical observations in context with pregnancies of women with hip arthroplasties using metal-on-metal implants. To our knowledge, this is the first report of such high levels of Cr and Co in a human pregnancy.

PURPOSES AND CLINICAL RELEVANCE

Although we cannot generalize from one case, the seemingly uneventful outcome of this pregnancy may reassure colleagues when counseling patients with high ion levels whether to carry a pregnancy to term.

Cobalt and chromium ion release after large-diameter metal-on-metal total hip arthroplasty

Seventy-five patients underwent unilateral metal-on-metal total hip arthroplasty using a large-diameter head. Serum levels of cobalt and chromium were determined. Significant increases in both cobalt and chromium were observed at 3 months (cobalt, 1.4 μg/L; chromium, 1.4 μg/L) compared with preoperative values (P < .001). At 1 year, the median cobalt and chromium levels were 2.3 and 2.1 μg/L, respectively, and the levels had increased significantly compared with 3 months (P < .001). There were no significant differences between levels of either metal at 1 or 2 years (cobalt, 2.3 μg/L; chromium, 1.6 μg/L). Pseudotumor occurred in 2 hips. Patients with large-diameter metal-on-metal total hip arthroplasty had higher circulating metal ion levels at 3 months and 1 year, with no additional significant increases at 2 years.