Failure analysis of a femoral hip stem made of stainless steel after short time of exposure

This paper describes a case study summarising the failure analysis of a stainless steel femoral stem, which failed prematurely within 36 months of exploitation in human body. In order to determine the mechanism of failure, a broken stem component were analyzed by means of macroscopic and microscopic obserwations and hardness measurements. Metallurgical obserwations revealed that the tested material does fulfill ASTM requirements. Scanning electron microscopy images revealed the presence of stress-induced cracking. The results of the hardness revealed significant nonuniformity from the surface towards the inner part of the stem. It is assumed that any discontinuity or defect on the fracture surface of the stem acted as preferential site for a crack nucleation and propagation by fatigue until the cross section of stem was not able to sustain a load generated by a patient.