Objective The risk of nickel ion precipitation during the clinical use of nickel-titanium shape-memory alloy bone implants exists

and the release of nickel ions from implants is difficult to test directly in vivo.Methods Phosphate buffered salt solution（PBS） was chosen as the test solution for the leaching of nickel ions from implants. The implants were placed in a container with a lid containing PBS

and the container was left in a temperature-stable controlled thermostatic incubator at (37±1)℃ for the corresponding set time points

and one set of blank tests and three identical parallel specimens were set at each time point for the determination of nickel content

and the concentration of nickel ions in the test solution The tests were performed with a graphite furnace atomic absorption spectrometer(AAS) and an inductively coupled plasma mass spectrometer (ICP-MS)device

respectively.Results The overall decreasing trend of nickel ion concentration released from the apparatus over time was observed at the end of the release cycle at the time point of 4 weeks of nickel ion release

and the average daily release amount per unit area measured by AAS was 0.37×10-3μg/(cm2·d). The average value of the cumulative release per unit area was 10.22×10-3μg/cm2. The average value of the daily release per unit area measured by ICP-MS was 0.29×10-3μg/(cm2·d). The mean value of the cumulative release per unit area was 7.9×10-3μg/cm2. The variability of the test results between AAS and ICP-MS was not significant

and the same trend of the results indicated that the test was reproducible. Conclusion This method can provide a basis for risk assessment of nickel-titanium shape-memory alloy bone implants to ensure that the precipitation of nickel ions during the clinical use of the implants will not cause harm to humans and ensure the safety of their clinical use.