Effect of Loading Frequency on the Fretting-Corrosion Degradation of the Stem-Head and Stem-Cement Interfaces in Hip Implants

Degradation by fretting-corrosion of the stem-head interface is considered the main source of the release of metal ions and debris, leading to adverse tissue reactions at the cemented total hip arthroplasty. The aim of this study was to investigate the effect of loading frequency on the fretting-corrosion degradation at the stem-head and stem-cement interfaces through electrochemical measurements during the benchtop testing. Different loading frequency conditions were investigated with the same number of cycles (1,000 cycles) to calculate the fretting current and Faraday mass loss. For both interfaces, there was a biphasic waveform response of the fretting current to the load applied, at 1 Hz, almost with phase opposition. An increase in the loading frequency (1 to 30 Hz) generated a higher fretting current for the stem-head (2.97 +/- 2.04 mu A to 7.66 +/- 2.46 mu A) and stem-cement (7.62 +/- 2.26 mu A to 25.48 +/- 5.35 mu A) interfaces. However, an increase in the loading frequency (1 to 30 Hz) reduced the Faraday mass loss of the stem-head (0.79 +/- 0.54 mu g to 0.07 +/- 0.02 mu g) and stem-cement (2.02 +/- 0.62 mu g to 0.32 +/- 0.12 mu g) interfaces because of a reduction in the overall testing time. Thus, there is a compromise relation between the fretting current and the Faraday mass loss, which must be considered when setting the loading frequencies in the fretting-corrosion benchtop testing of hip implants.