Laying the foundations towards understanding physiological kinematics after Total Knee Arthroplasty

• Applicants: Dr. Rainald Ehrig; Dr.-Ing. Philippe Moewis, Ph.D.
• Subject Area: Orthopaedics, Traumatology, Reconstructive Surgery
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 449409989

Over 9 million people in Germany suffer from constant pain because of knee joint osteoarthritis. Although conservative therapies are at the first line of defense, if they fail, replacement of the natural joint by total knee arthroplasty (TKA) remains the only option to alleviate pain and to regain joint function. Over 187’000 artificial knee joints were implanted during 2016 in Germany alone and numbers are at constant rise. However, despite 95% survivorship of TKA over a long term, about 20% of patients report dissatisfaction with the outcome. Non-physiological knee joint kinematics after TKA is considered as one of the main causes of this dissatisfaction. Knee joint kinematics after TKA is multifactorial and depends on factors such as the alignment of the implant components, the implant´s design and the conducted surgical technique, with all of them playing a relevant albeit not completely understood role. Understanding the interchange between such factors is essential to reach functional restoration of native knee biomechanics. However, little is known on the real in vivo knee joint kinematics and loading in patients, their inter-relationship as well as variability within and across patients. In this study, we aim at extending and applying our established technologies to our massive available amount of collected in vivo data (kinematics and loading) to unravel this inter-relationship. Developing thereby a unique database that eventually will allow us to predict – based on our already collected unique data set from previous and ongoing measurements - kinematic behavior from different geometrical designs as well as from different implant positioning and surgical procedures. Specifically, we aim to: 1) understand the amount of rolling and sliding between the implanted TKA components based on the changes in sagittal radius during different sets of loaded and unloaded activities. 2) To determine the changes in friction at the knee joint based on the axial pivot position as well as to transfer this knowledge to additional TKA designs. 3) To understand the implications of design features and surgical approach on kinematical parameters (anterior-posterior translation on the medial and lateral compartments and axial rotation). 4) The development of appropriate mathematical methodologies for the description of the relationship between the features and the kinematical outcome. Finally, to integrate this collected knowledge in rigid body models to achieve a systematic parameter modification with the aim of supporting the development of the aforementioned database to be used within TKA planning tools and to enable kinematic outcome predictions.

• DFG Programme: Research Grants
• Co-Investigators: Professor Dr.-Ing. Georg Duda; Professor Dr. Carsten Perka