Comparative analysis of surface wear from total hip prostheses tested on a mechanical simulator according to standards ISO 14242-1 and ISO 14242-3

This work presents a mechanical simulator of hip joint prostheses, designed to execute different wear test protocols. Two pairs of prosthetic components were tested. One pair was tested according to the kinematic specifications of ISO 14242-1 and the other one according to ISO 14242-3. Each pair is composed of a femoral head manufactured in surgical stainless steel (ASTM F138) and an acetabular component manufactured in UHMWPE (ASTM F648). The objective of this work is to investigate the effects produced by different kinematics presented by the above standards, considering the superficial damage that may occur in the prosthetic components after 1 million cycles. The superficial damages that occurred during the tests were examined by means of roughness measurements, observations with a stereomicroscope, scanning electron microscopy and chemical analysis by EDS. The results showed that the kinematics of the test proposed by ISO 14242-3 promoted more damage in the surfaces than the test with kinematics of ISO 14242-1. Significant increase of roughness parameters associated with plastic deformation, plowing and transference of materials between components was reported. The results after the test according to ISO 14242-1 showed an increase of Ra of the surfaces of approximately eight times while the parameter Rt showed an increase of around five times. For the prosthetic components tested according to ISO 14242-3, the Ra increased about thirteen times, while Rt increased more than ten times. Taking into account the results from the tested samples, namely, the significant superficial damage observed in the components after 1 million cycles, it is not recommended the in vivo use of this batch of prostheses.