Increased Mortality in Metal-on-Metal versus Non-Metal-on-Metal Primary Total Hip Arthroplasty at 10 Years and Longer Follow-Up: A Systematic Review and Meta-Analysis

Abstract

ImportanceThere are concerns about increased mortality in patients with metal-on-metal bearings in total hip arthroplasty (THA).ObjectiveTo determine the mortality and the morbidity in patients with metal-on-metal articulations (MOM THA) compared to patients with non-metal-on-metal articulations (non-MOM THA) after primary total hip arthroplasty.Data SourcesSearch of PubMed, MEDLINE, EMBASE, Web of Science, Cochrane, CINAHL, AcademicSearchPremier, ScienceDirect, Wiley and clinical trial registers through March 2015, augmented by a hand search of references from the included articles. No language restrictions were applied.Study SelectionTwo reviewers screened and identified randomised controlled trials and observational studies of primary total hip arthroplasty comparing MOM THA with non-MOM THA.Data Extraction and SynthesisTwo reviewers independently extracted study data and assessed risk of bias. Risk differences (RD) were calculated with random effect models. Meta-regression was used to explore modifying factors.Main Outcomes and MeasuresDifference in mortality and difference in morbidity expressed as revisions and medical complications between patients with MOM THA and non-MOM THA.ResultsForty-seven studies were included, comprising 4,000 THA in randomised trials and over 500,000 THA in observational studies. For mortality, random effects analysis revealed a higher pooled RD of 0.7%, 95%, confidence interval (CI) [0.0%, 2.3%], I-square 42%; the heterogeneity was explained by differences in follow-up. When restricted to studies with long term follow-up (i.e. 10 years or more), the RD for mortality was 8.5%, 95%, CI [5.8%, 11.2%]; number needed to treat was 12. Further subgroup analyses and meta-regression random effects models revealed no evidence for other moderator variables (study level covariates, e.g. resurfacing vs. non-resurfacing MOM) than follow-up duration. The quality of the evidence presented in this meta-analysis was characterized as moderate according to the CLEAR-NPT (for non-pharmacological trials) and Cochrane risk of bias Table.Conclusions and RelevanceMeta-analysis suggests there may be an increased long-term risk of mortality and revision surgery for patients with MOM THA compared to patients with non-MOM THA.RegistrationPROSPERO 2014:CRD42014007417

The risk of cardiac failure following metal-on-metal hip arthroplasty

“…There are only two previous studies, both negative and unpublished, 33,42 and no association was reported in a single, small meta-analysis. 13 In conclusion, we found a lower incidence of cardiac failure and mortality in patients with MoM arthroplasties compared with other types of arthroplasty of the hip in the first seven years after surgery. While there may be confounding factors by indication, these results should provide reassurance to clinicians and patients alike, regarding the cardiac sequelae associated with these devices.…”

“…Alongside localized effects, MoM prostheses have been associated with systemic complications such as cardiotoxicity and mortality. [9][10][11][12][13][14] Concerns have been recently raised about cobalt cardiomyopathy, particularly following the report of a three-fold increased risk in hospital admissions due to cardiac failure in a subgroup of men with MoM prostheses. 15,16 The findings have, however, been inconsistent.…”

“…15,16 The findings have, however, been inconsistent. 13,17,18 The symptoms and signs of cardiac failure are common in patients undergoing total hip arthroplasty (THA) and any association between the type of prosthesis and cardiac failure presenting at a later date, and usually to a different clinician, could easily be overlooked. 19 Record-linkage studies have been used to investigate the relationship between death due to cancer in patients who have undergone MoM THA, concluding that there is no increased risk.…”

Metal Ion Release after Hip and Knee Arthroplasty – Causes, Biological Effects and Diagnostics

“…In registries [42,44] as well as in a large cohort studies [45,46] patients with metal-containing implants appear to even have an increased life expectancy after MoM resurfacing. On the other hand, the results of a meta-analysis of a total of 47 studies by Pijls et al [47] showed a higher mortality risk in patients with metalon-metal hip arthroplasties compared to ceramic-on-polyethylene hip arthroplasties in long-term follow-up. Ultimately, due to the different methodologies, large number of implants included and only medium-term follow-up periods the results are difficult to interpret, and as yet there is still no clear conclusion regarding a potential cancer risk through metal implants.…”

Spotlight Commentary: A post approval look at anticoagulants

“…There are many health care interventions that are not medicines, which are launched upon patients without such careful monitoring. A good example are the metal‐on‐metal hip prostheses, but that is another story. So we need to keep looking for the needle in the haystack—even though we may come upon surprising and sometimes inappropriate discoveries.…”