Metal-on-metal or metal-on-polyethylene for total hip arthroplasty: a meta-analysis of prospective randomized studies

Background

There has been recent concern regarding the increased use of metal-on-metal total hip arthroplasty (MOM-THA) as an alternative to contemporary metal-on-polyethylene total hip arthroplasty (MOP-THA), and the choice remains controversial. We performed a meta-analysis to evaluate and compare metal ion concentrations, complications, reoperation rates, clinical outcomes and radiographic outcomes of MOM-THA and MOP-THA.

Methods

We performed a systematic review of English and non-English articles identified from MEDLINE, Embase, the Cochrane Central Register of Controlled Trials, PreMEDLINE and HealthSTAR. Metal ion concentrations, complications, reoperation rates and other outcomes of MOM bearings were compared with MOP bearings in THA based on relative risks, mean differences and standardized mean difference statistics.

Results

Eight prospective randomized trials were identified from 1,075 citations. Our results demonstrated significantly elevated erythrocyte, serum and urine levels of metal ions (cobalt and chromium) among patients who received MOM-THA. No significant differences in titanium concentrations or total complication or reoperation rates were found between MOM-THA and MOP-THA. Clinical function scores and radiographic evaluations were similar between the two groups.

Conclusions

This analysis found insufficient evidence to identify any clinical advantage of MOM-THA compared with MOP-THA. Although cobalt and chromium concentrations were elevated after MOM-THA, there were no significant differences in total complication rates (including all-case mortality) between the two groups in the short- to mid-term follow-up period. The MOM bearing option for THA should be used with caution.