Objectives. Modular dual-mobility (MDM) constructs are used to reduce dislocation rates after total hip replacement (THR). They combine the advantages of dual mobility with the option of supplementary acetabular screw fixation in complex revision surgery. However, there are concerns about adverse reaction to metal debris (ARMD) as a result of fretting corrosion between the metal liner and shell. Methods: The aim of this systematic review was to find and review all relevant studies to establish the outcomes and risks associated with MDM hip replacement. All articles on MDM THRs in the Medline, EMBASE, CINAHL, Cochrane Library, and Prospero databases were searched. A total of 14 articles were included. A random intercept logistic regression model was used for meta-analysis, giving estimated average values. Results: There were 6 cases of ARMD out of 1312 total. Estimated median incidence of ARMD from meta-analysis was 0.3% (95% CI 0.1 – 1.4%). Mean postoperative serum Cobalt was 0.81 μg/L (95% CI 0.33 – 1.29 μg/L), and Chromium was 0.77 μg/L (95% 0.35 – 1.19 μg/L), from 279 cases in 7 studies. Estimated median incidence of a serum cobalt or chromium ion measurement ≥1 μg/L was 7.9% (95% CI 3.5 – 16.8%), and ≥7 μg/L was 1.8% (95% CI 0.7 – 4.2%). Conclusions: ARMD is a rare but significant complication following total hip replacement using a MDM construct. Its incidence appears higher than that reported in non-metal-on-metal (MoM) hip replacements but lower than that of MoM hip replacements. MDM hip replacements are associated with raised serum metal ion levels postoperatively, but there was no correlation with worse clinical hip function within studies. Studies were poor quality and at high risk of confounding. Pending further work, MDM constructs should be used with caution, reserved for select cases at particularly high risk of dislocation

Abstract. Objectives. Modular dual-mobility (MDM) constructs are used to reduce dislocation rates after total hip replacement (THR). They combine the advantages of dual mobility with the option of supplementary acetabular screw fixation in complex revision surgery. However, there are concerns about adverse reaction to metal debris (ARMD) as a result of fretting corrosion between the metal liner and shell. Methods. The aim of this systematic review was to find and review all relevant studies to establish the outcomes and risks associated with MDM hip replacement. All articles on MDM THRs in the Medline, EMBASE, CINAHL, Cochrane Library, and Prospero databases were searched. A total of 14 articles were included. A random intercept logistic regression model was used for meta-analysis, giving estimated mean values. Results. There were 6 cases of ARMD out of 1312 total. Estimated median incidence of ARMD from meta-analysis was 0.3% (95% CI 0.1 – 1.4%). Mean postoperative serum Cobalt was 0.81 μg/L (95% CI 0.33 – 1.29 μg/L), and Chromium was 0.77 μg/L (95% 0.35 – 1.19 μg/L), from 279 cases in 7 studies. Estimated median incidence of a serum cobalt or chromium ion measurement ≥1 μg/L was 7.9% (95% CI 3.5 – 16.8%), and ≥7 μg/L was 1.8% (95% CI 0.7 – 4.2%). Conclusions. ARMD is a rare but significant complication following total hip replacement using a MDM construct. Its incidence appears higher than that reported in non-metal-on-metal (MoM) hip replacements but lower than that of MoM hip replacements. MDM hip replacements are associated with raised serum metal ion levels postoperatively, but there was no correlation with worse clinical hip function within studies. Studies were poor quality and at high risk of confounding. Pending further work, MDM constructs should be used with caution, reserved for select cases at particularly high risk of dislocation. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project