Date of Award
Doctor of Philosophy (PhD)
John D DesJardins
Recently, unicondylar knee arthroplasty (UKA) has seen a resurgence in clinical popularity, due to its increased success rate, improvement in implant designs, and more efficient surgical techniques. However, it continues to be a more technically demanding procedure and less forgiving compared to TKA [14,16-19]. The early reported failures due to the malalignment errors during surgery remain areas of concern clinically and experimentally [41-44,46]. In addition, the difference in the compliance between the UKA implant materials (metal-polymer) and the soft tissues in the un-operated comparted could also affect the load distribution on the knee joint. Advancement in medical technology and improvement in surgical techniques, such as computer navigation and robotic guidance, have allowed significant improvement in the accuracy of UKA compared to its preoperative plan. However, the real impact of the improved implant placement accuracy has yet to be demonstrated. Therefore, a more quantitative assessment of the effect of implant misalignment on the biomechanics of the knee joint is needed. There have been preliminary studies done in the area to better understand the biomechanical behavior of the procedure, but these are mostly performed using computer simulations [3,58]. It is difficult to accurately predict and validate the biomechanical behavior of a knee system using models with simplified geometries, structures, and material properties without experimental corroboration. Therefore, we propose to develop a custom-built knee rig in order to investigate the effect of mismatch in compliance after UKA, and the influences of varying surgical malalignment errors (Varus/Valgus) on the kinematics and contact pressures of the knee joint. Different similar models of the oxford-type knee rig have been evaluated and shown to be able to replicate the key kinematic characteristics of a normal knee . Our custom-built knee simulator will incorporate an advanced and accurate motion tracking system (Polaris Spectra) with a volumetric accuracy of 0.30 mm rms, and a knee joint pressure mapping system (K-scan, Tekscan Inc). The simulator will also consist of a novel detachable hip alignment assembly that allows adjustment of the femur to recreate the natural femoral neck angle, allowing the load bearing axis to pass through the center of the knee (Fig. 3.5). A winged assembly on the rig will allow the balancing of an electric motor that has a capacity of up to 10,000 N, allowing a full body weight simulation. A novel method of securing the pressure mapping sensor was developed to minimize sensor movement during testing and improve accuracy of the result (Fig. 4.10). Data collected from this work will not only contribute to the information needed to better understand the biomechanical behavior of the knee after UKA, but it will also provide a significant guidance and inputs for future computer simulation and experimental studies. Results from the experiment should provide information to help researchers and surgeons to evaluate and decide which tibial component angulation is optimal to the long term performance of the knee after the UKA procedure, and inform the greater understanding of UKA biomechanical behavior of the knee, specifically on articular contact load distributions and kinematics. The project will also promote collaborative work between bioengineering students, researchers, and clinicians, and make significant contribution to the current literature. The validated knee simulator will also serve as valuable platform for future biomechanical studies of the knee joint.
Rusly, Roy, "CONTRA-COMPARTMENTAL JOINT MECHANICS IN UNICONDYLAR KNEE ARTHROPLASTY" (2015). All Dissertations. 1522.