FAILURE OF ORTHOPEDIC IMPLANTS - 3 CASE-HISTORIES

Total joint replacement is an accepted treatment for pain and disability from diseased or damaged joints. Three case histories of failure analyses conducted on implants are presented. A series of 316L stainless-steel hip replacement components failed in fatigue by a unique mechanism of multiple cracks on the medial side of the stem and a fracture surface with crack initiation sites from both the medial and lateral surfaces. A Ti-6Al-4V alloy knee implant used for reconstruction of the knee after tumor surgery failed by fatigue through an embrittled weld microstructure around a cross pin. A cast Cobalt Stellite 21 alloy knee replacement failed because of the poor quality of the casting microstructure and the probable increase in stress concentration at the corners of the condyles arising from modifications to the casting. Each case study illustrates the contribution of material and design deficiencies to failure of total joint replacements.