Study characteristics of included epidemiological studies.

Gathered information refer to patients with at least one metallic part of the bearing being investigated on metal ions.
Studies were summarized due to multiple reporting of identical patient population.
Study design:.
CO: Cohort study, examination on metal ions at 2 or more points of time, reference group being different regarding state of surgery, implant type, bearing.
or the like is necessary; incl. metal ion measurement for all groups.
CC: Case-control study, cases with elevated metal ion concentrations, controls with not elevated metal ions concentrations, retrospective detection of exposition (bearing, implant typ); incl. metal ion measurement for all groups.
CS: Cross-sectional study, examination on metal ions at one point of time, reference group being different regarding state of surgery, implant type, bearing or the like is necessary; incl. metal ion measurement for all groups.
CA: Case series, examination of 2 or more persons on metal ions, at one or more points of time; incl. metal ion measurement.
1: Number of patients (with minimum one metallic part of the bearing) being examined on metal ions/total number of patients being examined on metal ions.
2: Rounded mean age of patients with minimum one metallic part of the bearing/rounded mean age of total group of examined patients.
*: Rounded weighted mean.
3: BMI  =  Body Mass Index.
4: THA  =  Total hip arthoplasty.
5: HRA  =  Hip resurfacing arthroplasty.
MoM: Metal-Metal bearing.
MoP: Metal-Polyethylene bearing.
MoC: Metall-Ceramic bearing.
CoC: Ceramik-Ceramik bearing.
CoP: Ceramik-Polyethylene bearing.
n. r.: Not reported.
6: Femorale head size 28–32 mm; small head.
7: Femorale head size ≥36 mm; large head.
**Incl. Protek, AlloPro, Sulzer Orthop., Centerpulse, Zimmer.
***Incl. Landander.
****Incl. Midland med. Technologies, Medizintechnik Wien, Endo Plus.
UCLA: University of California, Los Angeles.
$ distribution was not reported for the whole group.