Cobalt Levels and Pseudotumor Characteristics Vary due to Metal Ion Source: Modular Femoral Neck vs Metal-on-Metal Articulations

BackgroundThis study examines cobalt levels and pseudotumor characteristics in a non-recalled modular femoral prosthesis. We sought to determine relationships between serum cobalt levels and pseudotumors following modular and metal-on-metal (MoM) total hip arthroplasty (THA), the location and size of pseudotumors, and changes to pseudotumor grade over time.MethodsWe retrospectively evaluated a cohort of 190 primary THAs implanted with a dual-modular femoral stem by one surgeon from 2005 to 2013. One hundred seventeen THAs used a cobalt-chromium modular neck (CoCrMN) component and non-MoM articulation, 63 THAs had a titanium neck component and MoM articulation, and 10 had a titanium neck component and polyethylene liner. Serum ion levels were recorded for all patients. Pseudotumor grade and location were measured by musculoskeletal-trained radiologists.ResultsCobalt levels did not correlate to time after index arthroplasty. In the CoCrMN group, cobalt levels were elevated in 11 of 19 (57.9%) patients with pseudotumor compared to 14 of 19 (73.7%) in the MoM group. Pseudotumors were more often located lateral to the hip joint in the CoCrMN group compared to anteromedial following MoM arthroplasty. In CoCrMN THAs, pseudotumors were visualized in 12 of 51 (23.5%) initial MARS MRIs within 40 months compared to 5 of 66 (7.6%) performed later (P = .02).ConclusionPseudotumor characteristics differ between patients with CoCrMN designs vs those with an MoM articulation. Normal serum cobalt levels did not exclude the presence of a pseudotumor and routine MARS MRI should be included in follow-up of patients with this CoCrMN prostheses.     

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.     

Revision total hip arthroplasty with metal on metal bearing for ceramic bearing fractures

BackgroundDue to concern of potential metallosis caused by residual microscopic ceramic particles, metal-on-metal (MoM) bearing is deemed undesirable in revision total hip arthroplasty (THA) for ceramic bearing fracture. We determined whether MoM bearing is suitable to be used in revision THA for ceramic fractures and also evaluated whether this treatment increases serum iron levels compared with MoM bearing revision THA for polyethylene failure.MethodsBetween 2006 and 2012, 22 patients underwent revision surgery using MoM bearing (28 mm femoral head in 18 hips and 32 mm in 4 hips) for ceramic bearing fracture and followed average 52.1 months. We assessed radiological parameter and functional outcome using Harris hip score (HHS) and WOMAC score. Also, serum cobalt (Co) and chromium (Cr) blood tests were performed and compared with the result obtained from age, sex- and follow-up duration-matched patients with MoM revision THA for failed polyethylene bearing.ResultsThe mean HHS improved from 60.6 preoperatively to 90.3 at final follow-up. There were no changes in cup position, progression of osteolytic lesions, and measurable wear of MoM bearing articulation at final follow-up radiographs. There was one case of recurrent dislocation after surgery, which was treated with greater trochanter distal advancement and one case of deep infection, which underwent two-stage revision. Mean serum Co level (1.7 vs. 1.4 μg/dl; p = 0.211) and Cr level (0.70 vs. 1.01 μg/dl; p = 0.327) showed no significant difference.ConclusionsMoM articulation with liner cementation into the acetabular cup along with total synovectomy can be chosen in revision surgery for ceramic fracture with good midterm follow-up. However, the use of MoM bearing is indicated when the stem and metal shell can be retained and ceramic on ceramic or ceramic on polyethylene bearing cannot be selected. Also long-term outcome needs to be further evaluated.     

Clinical Outcomes,Metal Ion Levels,Lymphocyte Profiles,and Implant Survival Following Five Different Bearings of Total Hip Arthroplasty: A Mean 10-year Follow-up Study

BackgroundDifferent bearings have been used in total hip arthroplasty (THA), but the long-term performance is still controversial. The purpose of this study was to investigate whether there are differences when comparing THAs with 5 different bearings at a long-term follow-up of more than 10 years.MethodsFrom January 2010 to May 2012, 101 THA patients (134 hips) were divided into metal-on-metal group (MoM, 31 hips), metal-on-polyethylene group (MoP, 23 hips), ceramic-on-metal group (CoM, 21 hips), ceramic-on-ceramic group (CoC, 33 hips), and ceramic-on-polyethylene group (CoP, 26 hips). The mean follow-up period was 10.3 years. The Harris hip score (HSS), Western Ontario and McMaster Universities Osteoarthritis Index scores (WOMAC), range of motion (ROM), blood cell count, and liver-kidney function were measured. Serum and urine metal ion levels were measured using high-resolution inductively coupled plasma-mass spectrometry (ICP-MS) and a blood lymphocytes analysis was counted by flow cytometry.ResultsNo difference was observed in the HSS, WOMAC, ROM, blood cell count, or liver-kidney function among any of the 5 groups. Metal ion levels were significantly elevated in metal-containing bearings. Flow cytometry showed that no differences were found. Revision was performed due to pseudotumor in 3 patients. The implant survival rate was 96.7% and 93.3% for the MoM and CoC groups, which was significantly lower compared with other groups.ConclusionsMetal ion levels were elevated significantly in metal-containing bearings, especially in MoM THA patients. The implant survival rate was significantly lower in CoC and MoM THAs, which was mainly due to pseudotumor formation.Level of EvidenceTherapeutic Level II.     

Synovial Fluid Metal Ion Levels are Superior to Blood Metal Ion Levels in Predicting an Adverse Local Tissue Reaction in Failed Total Hip Arthroplasty

BackgroundAdverse local tissue reactions (ALTR) are associated with total hip arthroplasty (THA) failure in patients with metal-on-metal bearings and/or taper corrosion, which can also occur in metal-on-polyethylene articulations. Patients are monitored with blood cobalt (Co) and chromium (Cr) concentrations which do not always correlate with the degree of soft tissue reaction at revision THA. The purpose of this study was to determine how the blood and prosthetic hip synovial fluid levels of Co and Cr correlate with one another, and determine which concentration is more predictive of ALTR.MethodsSynovial fluid and blood samples were collected at the time of revision THA in patients with (n = 26) and without ALTR (n = 27). Whole blood, serum, and synovial fluid metal ion concentrations were correlated with one another and clinical findings.ResultsThe ratio of synovial fluid to whole blood Co concentration in ALTR and non-ALTR hips was 120:1 and 18:1 (P = .006). The mean ratio of synovial fluid to whole blood Cr concentration in ALTR and non-ALTR hips was 414:1 and 24:1 (P = .01). The mean synovial fluid Co/Cr concentrations were elevated in patients with ALTR compared with those without (2007.3 vs. 12.4 ppb, P = .007) and (3188.2 vs. 10.3 ppb, P = .02). The synovial fluid Co concentration was the most accurate test for detecting ALTR (cut off: 19.75 PPB, AUC 0.973).ConclusionIn patients with ALTR, synovial fluid Co and Cr levels were 120 times higher and 414 times higher than whole blood Co and Cr levels. Synovial fluid Co ion concentration was the most accurate in predicting ALTR.Level of EvidenceDiagnostic level II.     

Serum Metal Ion Levels in Cementless Metal-On-Metal Total Hip Arthroplasty: Long-Term Follow-Up Trends

Background

Long-term trends in serum metal ion concentration after metal-on-metal (MoM) total hip arthroplasty (THA) are unclear. In most studies, serum metal ion levels increase initially and remain constant during follow-up. However, there are no previous studies that evaluate the metal ion level longitudinally at multiple intervals over the long term. Increasing metal ion levels during the long-term follow-up of patients who underwent cementless MoM THA has been seen, so this study investigated those trends.

Safe Upper Limits of Serum Cobalt and Chromium Levels for a Metal-on-Metal Total Hip Bearing: A 10-Year Follow-Up Study

BackgroundLong-term survival of metal-on-metal (MoM) prostheses and the development of adverse reaction to metal debris (ARMD) around these bearings are still unclear. Serum levels of cobalt (Co) and chromium (Cr) are used as a screening tool to anticipate failure in MoM bearings and detect ARMD.MethodsOne hundred sixty primary large head MoM prostheses were followed up for 10 years. To estimate the revision risk, the cumulative incidence function (CIF) was used. Subdistribution hazard modeling was used to investigate the associations between cumulative incidence of revision for ARMD and Co levels, Cr levels, gender, age, head size, and cup inclination. Furthermore, the safe upper limits (SULs) for Co and Cr were determined.ResultsUnivariate analyses showed an increased risk in revision for ARMD in females (subdistribution hazard ratio [sdHR] 3.43, 95% confidence interval [CI] 1.01-11.7, P = .049) and cup inclination angles over 45° (sdHR 4.70, 95% CI 1.63-13.58, P = .004). In addition, a higher last measured Co level (sdHR 1.05, 95% CI 1.03-1.07, P < .001) and last measured Cr level (sdHR 1.21, 95% CI 1.14-1.29, P < .001) were associated with a higher probability of revision for ARMD. We determined our bearing-specific SULs at 4.1 parts per billion (ppb) and 4.2 ppb for Co and Cr, respectively.ConclusionGuidelines regarding follow-up and surveillance should include a complete clinical assessment with bearing-specific SULs of serum metal ion levels. For the M2a-Magnum MoM bearing we advise an SUL for Co and Cr levels of 4.1 and 4.2 ppb, respectively.     

Modular Neck vs Nonmodular Femoral Stems in Total Hip Arthroplasty—Clinical Outcome,Metal Ion Levels,and Radiologic Findings

Background

Modular neck femoral stem (MNFS) for total hip arthroplasty (THA) was introduced to optimize the outcome, but created concerns about pain, elevated blood metal ion levels, and adverse reaction to metal debris such as pseudotumors (PTs), related to corrosion between femoral neck and stem. We compared these outcomes in patients with MNFS or nonmodular femoral stem (NFS) THA.

Right Ventricle Dysfunction in Patients With Adult Cystic Fibrosis Enlisted for Lung Transplant

Knowledge of preoperative right heart function of adult patients with cystic fibrosis (CF) awaiting lung transplant (LUTX) is limited. The echocardiography of adult patients with CF enlisted for LUTX was retrospectively analyzed and compared with standards and invasive analyses (right heart catheterization, multigated radionuclide ventriculography). We included 49 patients (reported as mean ± standard deviation; 29 ± 9 years of age; forced expiratory volume in first second of expiration, 31% ± 11% predicted; lung allocation score, 36 ± 5; invasive mean pulmonary artery pressure, 17 ± 5 mm Hg; multigated radionuclide ventriculography right ventricle [RV] ejection fraction, 50% ± 9%). Patients had increased RV end-diastolic area, RV wall thickness, and increased pulmonary artery acceleration time with subnormal tricuspid annular plane systolic excursion, tissue Doppler positive peak systolic velocity, and fraction area change. Subnormal tricuspid annular plane systolic excursion (< 23 mm), tissue Doppler positive peak systolic velocity (< 14 cm/s), and fraction area change (< 49%) had high sensitivity and negative predictive value in predicting impaired RV.ejection fractionA good correlation between echocardiographic estimated and invasively measured systolic pulmonary artery pressure was observed (R² = 0.554, P < .001). Adults with CF awaiting LUTX have morphologic alterations of the right heart, with subclinical impairment of RV systolic function. Echocardiography may be used as a bedside, repeatable, and reliable noninvasive test to screen further deterioration in RV function while on the waiting list for LUTX. More prospective follow-up echocardiographic studies are necessary to confirm such a hypothesis.     

Pseudotumors in Small-Head Metal-on-Metal Total Hip Arthroplasties at a Minimum Follow-Up of 20 Years

BackgroundMetal-on-metal (MOM) surfaces in total hip arthroplasty (THA) have been used widely. Serum cobalt and chromium levels have been the standard investigation for follow-up examinations, but magnetic resonance imaging (MRI) with metal artifact reducing sequences has shown good results in detecting pseudotumors. The aim of this study is to survey a significant correlation among MRI findings, serum metal levels, and clinical scores in patients with small-head MOM implants and if serum cobalt and chromium levels are sufficient in detecting patients with pseudotumors in the long-term follow-up.MethodsAt a minimum follow-up of 20 years, 26 patients (29 THAs) of the original 98 patients (105 THAs) included in this study between November 1992 and May 1994 were available for follow-up examination. Clinical scores, serum metal ion levels, and MRIs were obtained.ResultsWe found mean serum cobalt levels of 1.87 μg/L (±3.44) and chromium levels of 2.23 μg/L (±2.96) and very good clinical and functional results (mean Harris Hip Score 88.6) in the long-term follow-up. Pseudotumors were detected in MRIs of 21 hips. There were no significant differences between patients with or without pseudotumors regarding serum metal levels and the correlation for clinical outcome scores, demographic data, and cup inclination. The cumulative rate of survival was still at 91.4% at 22.8 years.ConclusionThis study presents the first published data on small-head MOM hips, comparing metal ion levels, pseudotumors, clinical, and radiological results in a follow-up period of more than 20 years and reveals that serum metal levels are not significantly higher in patients with pseudotumors.Level of EvidenceTherapeutic Level III     

Levels of metal ions after small- and large-diameter metal-on-metal hip arthroplasty

Metal-on-metal (MOM) bearings for hip arthroplasty are increasing in popularity. Concern remains, however, regarding the potential toxicological effects of the metal ions which these bearings release. The serum levels of cobalt and chromium in 22 patients who had undergone MOM resurfacing arthroplasty were compared with a matched group of 22 patients who had undergone 28 mm MOM total hip arthroplasty (THA). At a median of 16 months (7 to 56) after resurfacing arthroplasty, we found the median serum levels of cobalt and chromium to be 38 nmol/l (14 to 44) and 53 nmol/l (23 to 165) respectively. These were significantly greater than the levels after 28 mm MOM THA which were 22 nmol/l (15 to 87, p = 0.021) and 19 nmol/l (2 to 58, p < 0.001) respectively. Since the upper limit for normal patients without implants is typically 5 nmol/l, both groups had significantly raised levels of metal ions. MOM bearings of large diameter, however, result in a greater systemic exposure of cobalt and chromium ions than bearings of small diameter. This may be of relevance for potential long-term side-effects. It is not known to what extent this difference is due to corrosion of the surfaces of the component or of the wear particles produced.     

MARS MRI Characteristics of Adverse Local Tissue Reactions in Taper Corrosion of Metal-On-Polyethylene THA Differ From Metal-On-Metal THA

BackgroundMetal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) has been recommended as a cross-sectional imaging modality in clinical evaluation of adverse local tissue reactions (ALTRs) in metal-on-metal (MoM) patients and metal-on-polyethylene (MoP) patients with taper corrosion. The aim of the study was to compare MARS MRI characteristics of ALTR in MoM total hip arthroplasty (THA) with ALTR in MoP THA with modular taper corrosion.MethodsA total of 197 patients with ALTR were evaluated: 86 patients with MoM THA; 37 MoP patients with head-neck taper corrosion; and 74 MoP patients with neck-stem dual taper corrosion. MARS MRI scans were evaluated to identify location, size, type of ALTR (I-III), and associated ALTR synovitis (cystic, solid, and mixed).ResultsMARS MRI characteristics of ALTR were significantly different between the MoM and MoP groups (P = .017). The MoP group demonstrated the highest proportion of thick-walled cystic masses type II (56.7% in head-neck taper corrosion MoP and 46.5% in dual taper corrosion MoP vs 28.7% in MoM), whereas the MoM group had the highest proportion of thin-walled cystic masses type I. MoM implants (96.8%) were significantly more likely to have ALTR in multiple locations compared with both MoP groups (P = .001).ConclusionThis study demonstrates that MARS MRI characteristics of ALTR differ by bearing type with a significantly higher percentage of mixed type and solid type ALTR in the taper corrosion MoP THA compared with MoM THA. This information provides clinically useful information in evaluation of symptomatic MoP and MoM THA patients for ALTRs.     

Higher Prevalence of Mixed or Solid Pseudotumors in Metal-on-Polyethylene Total Hip Arthroplasty Compared With Metal-on-Metal Total Hip Arthroplasty and Resurfacing Hip Arthroplasty

Background

Pseudotumors are a common finding in metal-on-metal (MoM) total hip arthroplasty (THA) and resurfacing hip arthroplasty (RHA). However, information on pseudotumors in metal-on-polyethylene (MoP) THA is limited.

Sensitivity and Specificity of Serum and Synovial Fluid Markers in Diagnosis of Infection in Head-Neck Taper Corrosion of Metal-On-Polyethylene Total Hip Arthroplasty

BackgroundThe accurate diagnosis of periprosthetic joint infection (PJI) in the setting of adverse local tissue reactions in patients with metal-on-polyethylene (MoP) total hip arthroplasty (THA) secondary to head-neck taper junction corrosion is challenging as it frequently has the appearance of purulence. The aim of this study is to evaluate the utility of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and synovial fluid markers in diagnosing PJI in failed MoP THA due to head-neck taper corrosion.MethodsA total of 89 consecutive patients with MoP THA with head-neck taper corrosion in 2 groups was evaluated: (1) infection group (n = 11) and (2) noninfection group (n = 78). All patients had highly crossed polyethylene with cobalt chromium femoral heads and had preoperative synovial fluid aspiration. In addition, serum cobalt and chromium levels were analyzed.ResultsThe optimal cutoff value for synovial white blood cell was 2144 with 93% sensitivity and 84% specificity. Neutrophil count optimal cutoff value was 82% with 93% sensitivity and 82% specificity. Receiver operating characteristic analysis of ESR and CRP determined optimal cutoff at 57 mm/h and 35 mg/L with 57% sensitivity and 94% specificity and 93% sensitivity and 76% specificity, respectively. There were no significant differences in metal ion levels between the infected and noninfected groups.ConclusionThe results of this study suggest that ESR and CRP are useful in excluding PJI, whereas both synovial white blood cell count and neutrophil percentage in hip aspirate are useful markers for diagnosing infection in MoP THA patients with head-neck taper corrosion associated adverse local tissue reaction.     

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).     

Serum metal ion concentration: comparison between small and large head metal-on-metal total hip arthroplasty

The purpose of this study was to compare serum metal ion concentrations (chromium and cobalt) in 3 groups, 2 with metal-on-metal articulations and a control metal-on-polyethylene group. Forty-six patients with good to well-functioning hips were recruited for the study. Serum ion levels of all patients were drawn, and Harris Hip Score, University of California, Los Angeles activity score, and radiographs were performed. Serum chromium concentrations were significantly lower in the large head group compared with the small head group (P = .013). There was no difference in the cobalt concentrations between the 2 groups (P = .087). There was a significant difference between both metal-on-metal groups when compared with controls for both chromium and cobalt levels (P = .0005 and P = .0004, control vs small; P = .001 and P = .0001, control vs large, respectively).     

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

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).     

Metal-on-Metal Bearing: Is This the End of the Line? We Do Not Think So

Background:

Recent studies have recommended the discontinuation of metal-on-metal (MoM) components in total hip arthroplasty (THA) because of adverse effects reported with large-diameter MoM THA. This is despite favorable long-term results observed with 28 and 32 mm MoM bearings.

Questions/purposes:

The aim of this study was to assess the value of calls for an end to MoM bearings as THA components. Specifically, we wish to address the risks associated with MoM bearings including adverse soft tissue reactions, metal ion release, and carcinogenic risk.

Methods:

The study evaluates the arguments in the literature reporting on MoM (adverse soft tissue reactions, metal ion release, and carcinogenic risk) and the experience of the current authors who re-introduced these bearings in 1995. They are balanced by a benefit–risk review of the literature and the authors’ experience with MoM use.

Results:

Adverse reactions to metallic debris as well as metal ion release are predictable and can be prevented by adequate design (arc of coverage, clearance), metallurgy (forged instead of cast alloy, high-carbide content), and appropriate component orientation. There is no scientific evidence that carcinogenicity is increased in subjects with MoM hip prostheses. MoM articulations appear to be attractive allowing safe hip resurfacing, decreasing the risk of THA revision in active patients, and providing secure THA fixation with cement in cages in severely deformed hips. MoM bearings in women of child-bearing age are controversial, but long-term data on metallic devices in adolescents undergoing spinal surgery seem reassuring.

Discussion:

Adequate selection of MoM articulations ensures their safe use. These articulations are sensitive to orientation. Fifteen years of safe experience with 28- and 32-mm bearings of forged alloy and high-carbide content is the main reason for retaining them in primary and revision THA.