[Causes of corrosive mechanical defects in isoelastic endoprostheses]

Within the framework of evaluation of endoprostheses of the hip joint reoperated at the orthopaedic clinic of the Institute for Postgraduate Medical Training, Faculty Hospital Na Bulovce in Prague in the course of six years the authors made a more detailed analysis of the group of isoelastic POLDI endoprostheses which displayed obvious signs of corrosion. The specimens from this group were subjected to evaluation focused on corrosion, metallographic and fractographic evaluation. In impaired wires of isoelastic endoprostheses the fracture surfaces have a fatigue character where a corrosion fatigue mechanism may be assumed as well fracture with a dominant mechanical component of stress. From the analysis of corrosion ensues that the connections of the wire shank with the head of the endoprosthesis are affected by crevice corrosion, the revealed fractures and cracks are most probably associated with corrosion fatigue. The construction of isoelastic prostheses of this type is the cause of corrosion processes which lead to mechanical failure. This should be the reason to refuse them for patients of any age group.