Both before and after carrying out friction tests, surface roughness measurements were proceeded. It was measured with direct contact method with using profilographometer. During surface roughness measurements contact tip of profilographometer was moving about 0.5 mm across Cinacalcet contact surface what allows to determine Ra parameter. Each measurement was repeated 5 times and then mean Ra value was calculated. The contact area of friction pairs was equal to 22 mm2.
Due to the fact that, in the clinical practice, only connection of the same metallic biomaterials as spinal instrumentation components is acceptable (because of the high risk of corrosion in the case of different metals), we decided to use homogeneous friction pairs (i.e. both sample and countersample are made of exactly the same materials). The investigated materials were: an austenitic steel AISI 316L and titanium alloy Ti6Al4V.
In order to simulate the mixed friction conditions and an aggressive surrounding influence, two solutions were applied – acidic sodium lactate (ASL) and Ringer's solution (RS). Before testing all metallic biomaterials were immersed in petals solutions for 24 h.