Corrosion And Mechanical Wear Of Biomedical Metallic Implants And Corresponding Health Aspects
Abstract
Total hip and knee arthroplasties are crucial for the restoration of damaged joints. If they fail in function or cause detrimental body reactions, this has devastating consequences for the patient. The complex chemical and mechanical conditions in the human body might influence the function and longevity of metallic implants. There is a mutual relationship between degradation of metallic alloys and corresponding biological responses. Both implant and patient-specific factors impact the failure of metallic alloys, resulting in early revision. This research aims to better understand, quantify, and ultimately prevent corrosion and tribocorrosion of materials and implants of relevance for hip and knee arthroplasties. Further, it aims at better diagnosing resulting metal allergies. In this study, the pattern and levels of biological damages on the hip trunnions and knee tibial baseplates were categorized and quantitatively evaluated by proposing standardized scoring systems based on optical microscopy (OM) and scanning electron microscopy (SEM). Tribocorrosion was predominantly observed across both implant types. Knee implants were more severely damaged than hip implants, except for tibial baseplates with optimized locking mechanisms. Patient-specific factors, comorbidities, and implant factors significantly correlated with the extent of damage. The effects of passivation with nitric acid and surface roughness on the corrosion of additively manufactured Ti6Al4V alloys, fabricated via laser powder bed fusion (LPBF), in benign (protein) and harsh (hydrochloric acid) solutions were studied. Rough surfaces provided a greater surface area favorable for more protein adsorption. The amount of metal ion release reduced after passivation. The LPBF Ti6Al4V alloys exhibited a reduced mechanical and chemical wear than wrought Ti6Al4V, resulting from finer microstructure, higher microhardness, and faster re-passivation. To evaluate current metal allergy diagnostic methods, chemical speciation modelling was used to study the bioavailable fraction of different aluminum and chromium salts under varying sweat pH and composition and suggest improvements to current diagnostic practices. Metal salt type, concentration, and sweat conditions alter the amount of bioavailable ions and influence the success of diagnosing related metal allergies. In all, this research contributes to improving and better utilizing orthopedic joint implants.