Robotic testing of total knee replacement designs
File(s)
Author(s)
Holthof, Sander Roger
Type
Thesis
Abstract
Total knee arthroplasty is a common surgical procedure to treat osteoarthritis. However, instability, caused by surgical technique, implant design and soft tissue imbalances, remains a complex issue, leading to TKA failure and pain in patients. The goal of this PhD was to investigate how articular geometries of knee replacements affect stability and kinematics, providing objective data to aid clinicians and implant manufacturers in implant selection and design.
Using a novel robotic technique, three distinct femoral and tibial geometries were investigated, first in isolation, then in vitro. Testing showed that implant geometry, independent of surgical technique, affects stability and kinematics of the knee. Higher constraint implants, with gradually reducing femoral radii or multiple femoral radii, provided better stability and rollback patterns more similar to the native knee, but restricted movement because of their conformity. A low constraint implant, with a single femoral radius, provides lower levels of stability and showed a higher reliance on soft tissues to stabilise the knee. Independent of implant design, TKA altered native knee kinematics and soft-tissue behaviour.
Modern robotic control software allowed force-controlled experiments to be carried out under continuous movement, as opposed to discrete flexion angles used in previous work researching knee replacement stability. This control software has been used for other joint stability studies in recent years; however, the work presented in this thesis is the first to use it to establish knee replacement stability throughout the full flexion-extension cycle of the knee under force-control.
Robotic testing managed to quantify the contributions of both implant designs and soft tissues across the range of flexion, providing quantitative data to evaluate implant designs. More rigorous preclinical testing, using modern testing systems, allows potential causes of instability to be identified before affecting patients.
Using a novel robotic technique, three distinct femoral and tibial geometries were investigated, first in isolation, then in vitro. Testing showed that implant geometry, independent of surgical technique, affects stability and kinematics of the knee. Higher constraint implants, with gradually reducing femoral radii or multiple femoral radii, provided better stability and rollback patterns more similar to the native knee, but restricted movement because of their conformity. A low constraint implant, with a single femoral radius, provides lower levels of stability and showed a higher reliance on soft tissues to stabilise the knee. Independent of implant design, TKA altered native knee kinematics and soft-tissue behaviour.
Modern robotic control software allowed force-controlled experiments to be carried out under continuous movement, as opposed to discrete flexion angles used in previous work researching knee replacement stability. This control software has been used for other joint stability studies in recent years; however, the work presented in this thesis is the first to use it to establish knee replacement stability throughout the full flexion-extension cycle of the knee under force-control.
Robotic testing managed to quantify the contributions of both implant designs and soft tissues across the range of flexion, providing quantitative data to evaluate implant designs. More rigorous preclinical testing, using modern testing systems, allows potential causes of instability to be identified before affecting patients.
Version
Open Access
Date Issued
2025-02-28
Date Awarded
2026-02-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Amis, Andrew
van Arkel, Richard
Sponsor
DePuy Synthes
Publisher Department
Department of Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)