Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Biomedical Engineering

Supervisor

Dr. Cynthia Dunning

2nd Supervisor

Dr. Trevor Birmingham

Joint Supervisor

Abstract

This thesis aimed to develop and assess biomechanical methods to assist in the evaluation of medial opening wedge high tibial osteotomy (HTO). Five studies using diverse methods were performed, including three-dimensional (3D) gait analysis, materials testing of HTO fixation plates, and dynamic radiography in patients after surgery. Study 1 compared external knee joint moments during walking before and after varus or valgus producing osteotomy in patients with lateral or medial compartment osteoarthritis, and in healthy participants. The results highlighted the importance of alignment on gait biomechanics with changes in frontal plane angular impulse highly correlated to changes in mechanical axis. Study 2 compared the 3D external knee moments before and after medial opening wedge HTO during level walking and during stair ascent. Long-term changes in knee moments after HTO were observed during both activities, with decreases in the peak knee adduction and internal rotation moments. Study 3 developed and tested a multi-axis fixation jig placed within a materials testing machine for assessing HTO fixation plates in a manner more representative of walking. The need to incorporate gait data into materials testing studies was highlighted, showing the importance of including a frontal plane moment during testing. Study 4 used this multi-axis fixation jig to compare flat to toothed HTO fixation plates under cyclic loading conditions. Preliminary results suggested little difference in the load at failure between the plates; however, the potential for the tooth to increase micro-motion across the osteotomy site and strain on the lateral cortical hinge should be a focus of future testing. Study 5 was a proof-of-concept study to test dynamic single-plane flat-panel (FP) radiography for use in detecting in-vivo micro-motion after medial opening wedge HTO. Preliminary results suggested dynamic FP radiography has the potential to assess fixation stability; however, results also suggested modifications in the registration algorithms may be required to increase confidence in distinguishing true motion from registration error. Overall, this thesis demonstrates that a mix of biomechanical methods can be used to advance medial opening wedge HTO, with particular focus on informing future methods of investigation to improve HTO fixation designs.

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