Use this URL to cite or link to this record in EThOS:
Title: Kinematics of posterior stabilised total knee replacements : a modelling and geometrical redesign study
Author: Van Duren, B. H.
ISNI:       0000 0004 2726 5519
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2008
Availability of Full Text:
Full text unavailable from EThOS.
Please contact the current institution’s library for further details.
Posterior stabilised total knee replacements incorporate a cam/post mechanism which is intended to increase posterior translation of the femur on the tibia in flexion. A review of the literature revealed that there were different opinions as to the effectiveness of posterior stabilised total knee replacement designs in improving kinematics. The aims of this thesis were to investigate why current posterior sta- bilised total knee replacement designs do not improve kinematics, and how cam/post design could be modified to improve posterior translation in flexion. A set of measurement tools to determine cam/post engagement, tibio-femoral kinematics and patello-femoral kinematics were designed, developed, and validated. These tools were assessed for accuracy using computer simulation and in vitro meth- ods. The tools were used to investigate the sagittal plane knee kinematics of a group of patients implanted with posterior stabilised knee replacement (Scorpio PS) and compare this data with the kinematics of normal knees. The cam/post mechanism was found to engage and to have a positive influence on the kinematic profile. How- ever, the kinematics of the Scorpio posterior stabilised design differed from those of the normal knee. A two-dimensional sagittal plane patient specific model of the knee was devel- oped. The model, driven by the knee flexion angle, was capable of predicting the patella tendon angle of implanted knees for a given relative tibio-femoral relation- ship. The model was validated against the in vivo data collected for the group of knees implanted with the Scorpio posterior stabilised implant. The model was then used to assess an existing knee design, the Vanguard, and compare the predictions to the data for normal knees. The Vanguard was found to have abnormal kinematics. The model was then used to optimise the design to achieve more normal kinematics. The modified design incorporated an improved cam/post mechanism and a reduction in articular surface constraint. To validate the new optimised design, a prototype was manufactured and tested using in vitro methods. The experiments showed the cam/post mechanism of the modified implant was more effective in improving the kinematic profile in flexion.
Supervisor: Gill, Richie ; Beard, David Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available