Hip replacement surgery is a tremendously effective and successful treatment for patients suffering from degenerative joint disease. However, revision surgery accounts for about 13% of hip implant surgeries in the U.S., costing $3 billion annually and presenting significantly increased morbidity and risk of complication for patients. Wear and/or failure of total hip arthroplasty (THA) bearing surfaces is one of the leading causes of device failure, either directly because of poor bearing articulation or through the detrimental effects of wear debris. The proposed work will develop and test a new bearing to be employed in a THA device. This novel approach will reduce bearing surface damage and wear when compared to state of the art approaches in bearing design. If this project is successful, the fundamental design of the bearing surface in THA could change for hundreds of thousands of patients every year. It is expected that this product design will reduce the United States arthroplasty revision burden. Laboratory research in failed orthopedic devices has informed the development team's understanding of the shortcomings of current industry designs. Independent studies of clinical retrievals provide compelling evidence that hard-on-hard hip bearing failure is driven by unanticipated dynamic head-to-rim contact. Wear, fatigue failure, and surface damage occur clinically. Thus, the goal of the proposed project is to develop new bearing surfaces for artificial hips that offer patients the very high wear resistance of hard-on-hard bearing couples and also offer the toughness and impact resistance of polymers such as ultra-high molecular weight polyethylene where most needed. The proposed work will establish feasibility through further development, manufacture, testing and modeling of the new bearing. The research plan will establish measureable and repeatable protocols for testing resilience and wear resistance of proposed surfaces, will proceed to validation in high contact stress loading that reflects true in vivo conditions, will establish proof of concept of new wear interfaces, and will develop a numerical model of the mechanical behavior of the bearing interface. Questions to be answered include validity of the simulation environment, resilience of the proposed material interface, and the ability to predict damage in the proposed bearing designs.
For patients with hip replacements, wear or mechanical failure of the bearing surfaces is a major factor in the need for hip revision surgery, which is costlier and carries higher risk of complication than primary surgery. Current-generation bearing alternatives are designed either to minimize wear debris or to compromise on wear to allow some compliance and impact resistance, with both approaches having significant shortcomings in terms of clinical outcome for the patient. The proposed project will develop and test novel bearing surfaces that optimize material choices for bearing design as dictated by explant analysis, and will use mechanical modeling to design for the challenges posed by in vivo use.