
Increased mortality with metal-on-metal total hip arthroplasty over long-term follow-up

Increased mortality with metal-on-metal total hip arthroplasty over long-term follow-up
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.
PLoS One. 2016 Jun 13;11(6):e0156051. doi: 10.1371/journal.pone.0156051. eCollection 2016Did you know you're eligible to earn 0.5 CME credits for reading this report? Click Here
Synopsis
38 randomized controlled trials and 9 observational studies were included in this systematic review and meta-analysis to compare mortality and morbidity rates between metal-on-metal total hip arthroplasty (MOM THA) and non-metal-on-metal THA (non-MOM THA). Results of the meta-analysis indicate no significant differences in mortality rate within 5 years, or from 5-10 years. However, mortality rate was significantly higher among MOM THA groups compared to non-MOM THA groups in studies with >10-year follow-up. Additionally, a trend towards a greater rate of surgical revision was observed in the MOM THA group.
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Was the validity of all of the studies referred to in the text assessed with use of appropriate criteria (either in selecting the studies for inclusion or in analyzing the studies that were cited)?
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Were the findings of the relevant studies combined appropriately relative to the primary question that the overview addresses?
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Discussion
Detsky AS, Naylor CD, O'Rourke K, McGeer AJ, L'Abbé KA. J Clin Epidemiol. 1992;45:255-65
The Fragility Index is a tool that aids in the interpretation of significant findings, providing a measure of strength for a result. The Fragility Index represents the number of consecutive events that need to be added to a dichotomous outcome to make the finding no longer significant. A small number represents a weaker finding and a large number represents a stronger finding.
Why was this study needed now?
Recent observational studies providing long-term follow-up have demonstrated an increased risk of mortality with the first generation of metal-on-metal total hip arthroplasty implants. However, conflicting data has been presented for second-generation metal-on-metal implants. Metal-on-metal total hip arthroplasty implants are still in use today in some settings and a comprehensive meta-analysis is needed to determine the mortality and morbidity of the different generations of MOM THA implants over the long-term.
What was the principal research question?
What are the overall mortality and morbidity rates of first- and second-generation metal-on-metal bearings when compared to non-metal-on-metal bearings in primary total hip arthroplasties evaluated in randomized controlled trials and observational studies?
What were the important findings?
- Mortality risk difference was assessed between MOM THA and non-MOM THA at three different follow-up periods; <5 years, 5-10 years, and >10 years. No significant difference was observed within 5 year follow-up (13 RCTs; RD 0.1% [95%CI -1.3% to 1.0%]) or from 5-10 year follow-up (9; RD 0.7% [95%CI -3.0% to 1.7%]). In studies with >10-year follow-up, a significantly higher rate of mortality was observed among MOM THA groups compared to non-MOM THA groups (3 RCTs/1 Observational; RD 4.4% [95%CI1.4% to 7.4%]).
- Observational studies of first-generation MOM THA demonstrated a trend toward increased mortality compared to non-MOM THA (RR 1.05) This finding was in line with the results from RCTs. Observational studies evaluating second generation MOM demonstrated a decreased risk of mortality for MOM THA compared to non-MOM THA, which was in contrast to long-term results from RCTs.
- Morbidity in the form of surgical complications was reported in 26 RCTs, all evaluating second generation MOM THA in comparison to non-MOM THA. The risk of revision was greater in the MOM group RD: 0.8% [95%CI -0.1% to 1.7%] I-squared 0%, but this difference was not significant.
- The risk of cancer was reported in 4 observational studies: 1 evaluating first generation MOM THA and 3 evaluating second generation MOM THA. The first generation MOM THA demonstrated a greater risk of cancer compared to non-MOM THA, but this increased risk was not significant, while the second generation demonstrated no difference compared to non-MOM THA.
What should I remember most?
The long-term mortality rates appear to be increased in metal-on-metal total hip arthroplasty compared to non-metal-on-metal hip arthroplasty, while mortality rate within 10 years does not appear to differ significantly. Additionally, the rate of surgical revision appears to be higher with the use of metal-on-metal total hip arthroplasty compared to non-metal-on-metal total hip arthroplasty.
How will this affect the care of my patients?
The results of this meta-analysis demonstrated a higher rate of mortality with the use of metal-on-metal implants in total hip arthroplasty in randomized controlled trials with long-term follow-up. In addition to the higher rate of mortality, there was a trend towards increased morbidity requiring surgical revision. The result from this study highlights the need for patients who have received a metal-on-metal implant in the past to be closely followed. Additionally, the result of this trial indicates that there is no case for the use of metal-on-metal THA implants due to the increased risk of mortality.
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