Increased mortality with metal-on-metal total hip arthroplasty over long-term follow-up .
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OrthoEvidence Journal (OE Journal) - ACE Report
OE Journal. 2017;5(2):6 PLoS One. 2016 Jun 13;11(6):e0156051. doi: 10.1371/journal.pone.0156051. eCollection 201638 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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Detsky AS, Naylor CD, O'Rourke K, McGeer AJ, L'Abbé KA. J Clin Epidemiol. 1992;45:255-65
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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?
- 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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