Comparison of chromium and cobalt serum levels between a modular neck stem and its monoblock counterpart in primary total hip arthroplasty

Background The addition of junctions in modular stems implies a greater susceptibility to corrosion. Purpose The aim of this study is to compare serum chromium and cobalt levels after using a bimodular stem and its monoblock counterpart in primary total hip arthroplasty. Postoperative clinical scores were also compared. Patients and methods A prospective cohort study between 2012 and 2015 was designed. One arm of the cohort included patients with the cementless modular neck stem H-Max M® and the other with the cementless monoblock stem counterpart H-Max S®. Results No statistically signifcant diference was found in chromium value between groups (p=0.621) at two years postoperative. Cobalt value was higher in the modular group (p=<0.001). No statistically signifcant diference was found in clinical postoperative scores except for the Harris Hip Score, with better results at six months in modular group (p=0.007). Conclusions Higher serum cobalt level in the modular group has limited the use of modular stems in our daily practice. Advantages of modular stem were not found. Level of evidence II. Keywords Total hip arthroplasty · Modular neck stem · Serum metal ion level