Date of Award

6-2019

Document Type

Masters Thesis

Degree Name

M.S.

Organizational Unit

Daniel Felix Ritchie School of Engineering and Computer Science, Mechanical and Materials Engineering

First Advisor

Chadd W. Clary

Keywords

Total knee replacement, Cementless

Abstract

Initial stability of cementless total knee replacement (TKR) components is crucial to establish bony ingrowth into the porous interface surface and long-term fixation, however, few cementless patellar implant micromotion tests have been developed. Previous studies were all focused on qualifying tibial micromotion, experimentally measuring relative motion between the tray and bone or computationally predicting micromotion at the tibial tray-bone interface using finite element models. The goal of this study was to develop and validate computational models for patellar implant micromotion under implant-specific loading conditions and analyze the performance of implant-bone interface micromotion for different patellar implant designs. Seven different loading profiles generated from patients with total knee replacement performing a single-leg lunge were experimentally applied to eleven samples of cementless anatomic and medialized dome patellar components implanted into patellar SawbonesTM constructs using the AMTI VIVO joint simulator. Eight patella samples were implanted into 12.5 lb/cubic foot (PCF) polyurethane foam synthetic bone while three samples were implanted into PCF 20 synthetic bone to quantify the relationship between the observed micromotion and material properties. The relative motions between the implants and synthetic bones were captured by a digital image correlation (DIC) system, which was used to validate a finite element model prediction of bone-implant micromotion. The computational model was able to accurately distinguish between the loading conditions and locations on the implant surface where the micromotion was measured (lateral, central, medial), and capture the observed experimental trends. The average RMS difference and the correlation between experimentally measured and model-predicted displacements were 22.4 μm and 0.97 for the 32-mm medialized dome patellar implant, 39.9 μm and 0.96 for 35-mm anatomic patella, respectively. This study found that the both patellar implant type (medialized dome versus anatomic) and size influenced the micromotion of the patellar implant and should be considered when choosing the best implant for a patient. The validated computational model developed in this study can facilitate and enhance the pre-clinical assessment of new patellar implants and to investigate early clinical performance of the designs.

Publication Statement

Copyright is held by the author. This work may only be accessed by members of the University of Denver community. The work is provided by permission of the author for individual research purposes only and may not be further copied or distributed. User is responsible for all copyright compliance.

Rights Holder

Xuzheng Han

Provenance

Received from author

File Format

application/pdf

Language

en

File Size

81 pgs

Discipline

Biomechanics, Mechanical engineering

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