Metallurgical aspects of failure in a broken femoral HIP prosthesis

In this research failure of femoral hip prosthesis, made of AISI 316 L stainless steel, in a 69 years old patient with a weight of 70 kg was investigated. Replacement of the damaged cartilage and bone of the hip joint with prosthesis component through Total HIP Arthroplasty (THA) is a widely used surgery. Patients with this type of implants are anticipated to have a normal daily life with capability of performing routine physical activities for a period of 15 years. However, in investigated case, the failure had occurred in <10 years. Optical and electron microscopy as well as hardness measurements were conducted to investigate possible causes of the failure. Results showed that high cycle fatigue was the failure mechanism. Microstructure of the investigated hip consisted of surprisingly high density of inclusions which should have caused the initiation and growth of fatigue cracks. Possible failure scenarios and mitigation strategies have been discussed in this regard.