Component Placement in Hip and Knee Replacement Surgery: Device Development, Imaging and Biomechanics

Abstract

Total joint replacement replaces the worn surfaces of arthritic joints with artificial components. This usually results in significant pain relief, but problems persist in some patients. An important contributor to postoperative complications following joint replacement is component malalignment. The goal of the work described is to improve component placement in total hip and knee arthroplasty. As one of the main objectives in this work, an adjustable mechanical device, called Optihip, was developed and tested to improve the accuracy of acetabular cup alignment in hip replacement surgery. An ex vivo study demonstrated the accuracy and feasibility of the device for guiding orientation and depth of the acetabular cup. With respect to knee replacement surgery, preoperative and postoperative weightbearing patellofemoral and tibiofemoral kinematics throughout the range of motion, using calibrated sequential-biplanar radiographic imaging at 8 flexion angles, are reported for nine subjects before and at least one year after total knee arthroplasty (TKA). Changes in the articular geometry of knee joints for the same nine subjects are also investigated by matching the three-dimensional (3D) implant models to the 3D bone-implant volume from computed-tomography (CT) imaging. Relationships between the subjects’ quality of life (QOL) and changes in knee articular geometry and kinematics are also evaluated. There were significant differences between pre-TKA and post-TKA kinematics in this pilot study, although not for all degrees of freedom. Patellofemoral and femoral analyses showed that the knee shape and geometry changed in numerous significant ways as a result of the TKA. There were also significant correlations between shape, kinematics and QOL parameters. Postoperative QOL in this cohort was better for a more lateralized proximal femoral groove, smaller changes in femoral condylar dimensions, more lateralized patellofemoral mediolateral translation and shift, less patellar tilt, more internal TF internal-external rotation and fewer individual shape and kinematic high/low values. Postoperative patellar tracking followed the femoral component groove more closely than the original preoperative tracking, suggesting that the femoral groove has more control over patellar tracking than the soft tissues.