Failure Analysis of Modular Hip Implant

Author

Nishi Shah, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2012

Degree Name

Master of Science

Department

Biomedical Engineering

First Advisor

Filip, Peter

Abstract

Biomaterials is a systematically, pharmacologically inert substance designed for implantation within or incorporation with a living system. The ultimate goal of biomaterials is to restore function of living tissues and organs of the body. Chemical stability, mechanical behavior and biocompatibility in body fluids and tissues are basic requirements for successful application of implant materials in hip replacements. The field of biomaterials has become a vital area, as these materials can enhance the quality and longevity of human life and the science and technology associated with this field has now led to multi-million dollar business. The thesis focuses mainly on fractured analysis of retrieved titanium-alloy modular hip implants, even though there exists biomaterials made up of ceramics, polymers and composite materials As it is well known that a good biomaterial should possess the fundamental properties such as better mechanical and biological compatibility and enhanced wear and corrosion resistance in biological environment. The primary purpose of this thesis was to identify the reasons which lead to fracture of implant retrieved from 60years old male implanted for a 16 month time. The retrieved Implant was sterilized for two hours to overcome bio hazardous condition. The fractured area of implant sleeve and stem was cut with help of machine ISOMET BUEHLER 4000 consisting of diamond saw. The cut sample was placed into physiological solution (0.9% NaCl in H2O), and was maintained at room temperature over night. Samples were then thoroughly brushed with help of toothpaste and tooth brush to get rid of tissue deposits and blood stains so as to get clear picture under SEM. Fractures sample was than observed under Scanning Electron Microscope and a detailed study revealed fretting corrosion and fatigue failure were main cause of implant failure. After examining under SEM, sample was than prepared to be polished by covering it with epoxy and using BUEHLER polishing machine and sand paper from 240-1200 grid and finally a micro cloth to smoothen the surface. After sample being polished, it was immersed in Kroll solution for etching and observing under microscope to figure micro-structural changes.