Failure analysis of a fractured stainless steel femoral bone plate

Abstract

This study investigated a femoral bone plate that fractured after 6 months of use in a patient who had already experienced a similar implant failure. Chemical analyses, Vickers hardness measurements, and metallographic and fractographic examinations showed that the compression plate was following the chemical and microstructural requirements set by the ISO 5832 standard, and no material or manufacturing defects could be associated with the premature failure of the plate. The fracture occurred on the seventh of the fourteen holes of the plate and the failure mode was identified as bending fatigue. The main fatigue cracks nucleated on the edge of the compression hole and propagated through the plate towards the bone. Finite elements analysis results confirmed that fatigue crack nucleation sites were regions of maximum stress concentration. Lack of bone healing was the most probable cause for the excessive loading of the plate, and the failure might have been prevented with better stabilization of the bone fracture region, although analyses of surgical and post-operative medical procedures were outside the scope of this investigation. Additionally, a brief discussion regarding orthopedic implant failures in Brazil was conducted. By analyzing 25 other failure cases, it was found that most of them are related to the device itself and might have been prevented through a better technical certification process and implant monitoring by the national health regulatory agency.