Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Health and Rehabilitation Sciences

Collaborative Specialization

Musculoskeletal Health Research

Supervisor

Birmingham, Trevor B.

2nd Supervisor

Willing, Ryan

Co-Supervisor

Abstract

Knee OA is a complex disease where aberrant gait biomechanics may contribute substantially to progression of structural joint damage and symptoms. Medial opening wedge high tibial osteotomy (MOWHTO) is a limb realignment surgery intended to lessen loads on the medial compartment of the tibiofemoral joint in patients with medial dominant knee OA and varus alignment. As it is difficult to directly measure knee joint contact forces (KJCF) the effect of MOWHTO on joint loading remains unclear. Neuromusculoskeletal (NMSK) modelling can estimate these forces. Therefore, purposes of this thesis were to: 1) develop an electromyography (EMG)-informed NMSK modelling framework to predict tibiofemoral medial and lateral compartment KJCF during walking in patients with medial dominant knee OA and varus alignment, and 2) evaluate the effect of MOWHTO on KJCFs during walking.

Chapters 2 and 3 sought to better understand the effects of adjusting patient-specific model parameters. Chapter 2 evaluated results from patient-specific NMSK models using two control modes. Results indicated the EMG-assisted control mode, compared to the EMG-driven control mode, provided greater consistency between knee flexion torques and KJCFs were better aligned with previous studies. Chapter 3 compared patient-specific EMG-assisted models with a neutral varus angle (0º) and a patient-specific varus angle. No statistically significant differences occurred in the KJCFs between models after adjusting this parameter. Chapter 4 investigated: 1) the effect of medial opening wedge HTO on medial and lateral tibiofemoral compartment KJCFs during walking, using the established patient-specific EMG-assisted modelling framework, 2) changes in the external knee adduction moment (EKAM) and muscle co-contraction indices (CCIs), and 3) associations between the changes in medial compartment KJCF and EKAM and CCIs. There were moderate improvements in medial KJCFs (standardized response mean, SRM>0.60) and small-to-large reductions in the EKAM (SRM>0.90) and CCIs (SRM>0.20). Correlations between changes in medial KJFCs and EKAM and muscle CCI were low-to-moderate (r

Results from this thesis contribute to the development of a patient-specific EMG-assisted modelling framework to predict KJCF during walking in patients with medial dominant knee OA and varus alignment. The EMG-assisted NMSK modeling framework suggests medial opening wedge HTO substantially decreases knee medial compartment load during walking.

Summary for Lay Audience

Knee osteoarthritis (OA) is a complex disease, for which “bowed legs” and altered activity from muscles can contribute to inappropriate loads on the knee during walking. Conducting a gait analysis to simulate the patient’s walking patterns may provide an estimate of these loads acting on the knee joint with patient-specific computer models. Therefore, purposes of this thesis were to: 1) develop a computer modelling framework to predict knee loads during walking in patients with medial dominant knee OA and bow-legged alignment, and 2) evaluate the effect of an alignment surgery on knee loads during walking.

Chapters 2 and 3 sought to better understand the effects of adjusting computer model parameters on its predictions. Chapter 2 evaluated and compared results that were simulated using a model that utilized muscle activity that was obtained as the patient was walking. The second model uses the same muscle activity patterns but also incorporates external forces that act on the joints. Joint loads calculated using the modified muscle activation model more closely resembled joint loads that were reported in other studies. Chapter 3 also evaluated and compared results that were simulated using two separate models. The first model was scaled to have neutral lower limb alignment and the second model was scaled to match the patient’s bow-legged alignment. Results were similar using both models regardless of the adjusted parameter.

Chapter 4 investigated 1) the effect of the alignment surgery on knee loads during walking using patient-specific computer models, 2) changes in measures associated with knee loads, and 3) explored associations with change in knee loads. There were moderate improvements in knee loads. Large reductions also occurred in parameters that are associated with knee loads. Associations between changes in knee loads and parameters associated with knee loads were low-to-moderate. Results from this thesis contribute to the development of a patient-specific computer modelling framework to predict knee loads during walking in patients with medial dominant knee OA and bow-legged alignment. The patient-specific computer model suggests the alignment surgery substantially decreases knee loading during walking.

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