Acetabular Defect Augmentation with Kryptonite Bone Cement in Total Hip Replacement: Stability Analysis

The pelvis connects the upper and lower extremities of the body’s musculoskeletal system and plays an extremely important role in locomotion, balance, and stability, as well as load transfer across the joint. The repetitive loading of the hip joint leads to degeneration of the surrounding articular cartilage and cortical bone and can result in acetabulum bone defect and osteoarthritis. In order to restore normal hip function, a number of patients undergo a total hip replacement surgery. Acetabular defects and repair in the presence of total hip replacement are seen in patients with severe arthritis or extensive bone loss at the hip joint because aseptic loosening of the acetabular cup component following initial THR can lead to additional bone loss over time. The study aims to quantify the displacement and rotation of the acetabular cup into the acetabulum following THR using the mechanical testing of cadaveric specimens with and without the presence of an acetabular wall defect augmented with Kryptonite bone cement. The results suggest that defect augmentation with Kryptonite bone cement during acetabular wall reconstruction allowed for a successful reconstruction of the wall, but that the response is dependent on the loading conditions. Both experimental studies utilizing cadaveric specimens and finite element analysis studies usually complement well the clinical investigation of cup fixation. In this thesis research, a finite element model suitable for patient-specific analysis was developed and validated with in-vitro measurements. The use of a finite element model helps to quantify the effect of various factors including the amount of under-reaming and the force used to insert the acetabular cup on the micromotion and stress due to simulated initial post-operative loading. The results indicate that for a lesser amount of under-reaming less cup insertion force is needed, and approximately the same percentage of surface contact at the cup-bone interface can be achieved with only a slight difference in micromotion of the cup occurs. Finally, a finite element model was developed in which an acetabular defect was introduced in order to have an understanding of the initial cup fixation and stress on the bone during immediate post-operative loading and for various bone apparent densities. The results show that defect reconstruction with bone screws and Kryptonite results in a re-distribution of stress into the bone, particularly at the site of defect reconstruction. The results of this study can provide useful information for clinicians performing total hip replacement with and without the presence of acetabular wall defects.