Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Chemistry

Collaborative Specialization

Musculoskeletal Health Research

Supervisor

Hedberg, Yolanda

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.

Summary for Lay Audience

It is not completely guaranteed that hip and knee replacements last for a long time inside the human body. This research studies the reasons behind failure of metallic implants earlier than expected and the contribution of both patient and material factors to the failure.

This study analyzed hip and knee arthroplasties and discovered various types of damage that metallic implants experience during their operation. Loads from weight and movement from daily activities and the chemistry of body fluid cause metallic implant degradation. Knee implants undergo harsher conditions inside the human body, so they appear to be more damaged than hip implants, except when they have a specific design. Metallic implants might corrode, wear down, and release metal ions to the surrounding biological environments.

One of the commonly used materials for biomedical implants is titanium-based alloys. This study investigates how different surface treatments influence the corrosion and metal ion release of titanium alloy when it is exposed to the protein-containing and acidic solutions. Those simulate the solutions that exist in the human body.

Since 3D printing has been widely used to fabricate metallic implants, this research compared the effect of manufacturing, conventional versus 3D printing, on the performance of titanium alloys when they experience corrosion and sliding at the same time. The 3D printing technique could offer better features for the application of titanium alloys as metallic implants.

Metal allergy is one of the side effects resulting from released metal ions. Patch testing is a good approach for determining whether someone is allergic to a particular metal or not by using a metal salt. The efficiency of patch testing depends on the body’s sweat composition, pH, and the concentration and composition of the metal salts, and that is why some patients show false-negative results in that diagnostic method, which we suggested to improve accordingly, so that all patients can be diagnosed correctly.

Overall, this research aims to provide knowledge about unfavorable implant failure and help to obtain better designs and materials choices for the right group of patients, to obtain prolonged implant service life, reduced revisions, and improved quality of life.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

Available for download on Thursday, January 21, 2027

Share

COinS