Evaluating the Biomechanical, Functional, and Clinical Outcomes of Bicruciate Stabilized Total Knee Arthroplasty
Abstract
Total knee arthroplasty (TKA) is the only solution for treating arthritis of the knee joint. Although it is successful at reducing pain and returning function to affected joints, one in five patients still report dissatisfaction following their operation. Bicruciate stabilized (BCS) TKA was developed to improve outcomes by replicating normal knee structure and function. The biomechanical, functional, and clinical outcomes for the BCS design were investigated in this thesis through radiographic imaging techniques, wearable sensor systems, and questionnaires in a cohort of TKA patients.
A stereo x-ray technique, called radiostereometric analysis (RSA), assesses implant fixation by tracking micromotion of TKA devices relative to the bone. Risk of implant loosening can be predicted based on the magnitude of these micromotions. This thesis found micromotion of the BCS TKA was within safe thresholds for both the gap balancing and measured resection techniques, indicating sufficient fixation to the bone occurs and the BCS TKA is not expected to have elevated revision risks due to implant loosening.
The exact cause of patient dissatisfaction after TKA is unknown. This thesis sought to find any differences in objective data between satisfied and dissatisfied patients with a BCS TKA. RSA was used to measure implant micromotion and tibiofemoral contact kinematics. A sensor system tracked measures of patient function during a timed-up-and-go functional test, and patient-reported outcomes were collected. We found no difference in implant micromotions or patient function between satisfied and dissatisfied patients. However, dissatisfied patients had more anterior contact on the lateral condyle of the knee in early flexion, and more pain and unmet expectations.
Finally, correlations were found between implant micromotion and tibiofemoral contact kinematics. Contact patterns indicating reduced posterior femoral rollback in the lateral compartment correlated with greater implant micromotion. Since BCS TKA aims to replicate normal knee kinematics and guide posterior rollback, it was concluded that undesired kinematics resulted in greater micromotions, and a greater risk of implant loosening.
Overall, the restoration of kinematics—particularly in the lateral compartment—in BCS TKA appears to be important for reducing implant migrations, improving pain and feeling in the knee, and ultimately, enhancing patient satisfaction.