Failure analysis of a total hip prosthesis implanted in active patient

This work presents an analysis of a total hip prosthesis that failed in service prematurely within 5 years. The prosthesis presented a fractured stem that was extracted from a 46 year old male patient, 75 kg weight and 1.76 m height. In order to determine the origin of the failure, the femoral stem component was analyzed by means of visual inspection; optical microscope (OM), scanning electronic microscopy (SEM) and energy disperse spectroscopy (EDS). The investigation showed that the crack had originated due to a high stress concentration on the anterolateral corner section of the stem. Any discontinuity or defect on the prosthesis surface in this location acted as preferential site to nucleate a crack which propagated by fatigue until the cross section was not able to sustain an eventual high load produced for the active patient.

Research highlights
► Although there were big sulfur contaminant particles on the fracture surface, this was not the main failure mechanism.
► The crack formation originated due to a high stress concentration on the anterolateral corner section of the stem.
► Any slight discontinuity or defect on this section of the surface acted as a preferential site to nucleate a crack which was propagated by the fatigue mechanism until the large sulfur contaminant chains leading to a defective area which was not able to support an eventual high load in the active patient.