Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Biomedical Engineering

Supervisor

Willing, Ryan

2nd Supervisor

Getgood, Alan

Co-Supervisor

Abstract

Despite decades of clinical, experimental, and computational research on knee joints, the lack of understanding of ligaments' contribution in knee biomechanics has hindered efforts to accurately predict the effects of diseases, injuries, and the long-term effectiveness of reconstruction surgeries. Therefore, a thorough understanding of the biomechanical contributions of knee ligaments is essential for developing successful rehabilitation and surgical planning after injury.

Contemporary, a growing number of studies have been conducted using cadaveric knees to quantify ligament contributions to normal and pathological knee biomechanics. In these studies, the anatomic variability in patient populations is present in cadaveric specimens, making study findings more applicable. However, studying the effects of injuries and surgical interventions on cadaveric specimens can result in irreparable tissue damage, requiring the use of new specimens, which is expensive and time-consuming. Alternatively, computational modeling has been used to parametrically analyze knee ligaments and evaluate their responses to various pathologies and treatments. However, these models are difficult to develop fully validate. Even after a model has been developed, the predictions based on that model may not be applicable to all subjects. Recent studies have focused on combining cadaveric experiment-based results with subject-specific multibody or finite element models. In these studies, experimental results are used as a basis for post-hoc tuning of computational models. While this approach may allow models to reproduce the system-level response of the joint, inaccuracies in how the ligaments are modelled may be buried amongst the other simplifications in the model. It is possible that these simplifications lead to unrealistic forces and inconsistent results.

The purpose of this thesis was to develop a combined experimental-computational technique for characterizing the biomechanical contributions of knee ligaments to normal and pathological joint biomechanics. In this approach, a computer simulation of soft tissues (virtual ligaments) was developed to mimic the force-length behavior of ligamentous structures. The designed virtual ligaments were used to stabilize knee joints on a joint motion simulator. Using virtual ligaments on knee joints bridged the gap between experimental and computational approaches, which can predict experimental data while parametrically simulating ligament repair and injury.

Summary for Lay Audience

Knee ligaments are connective tissues that hold bones together and guide knee motion. With increases in the number of people participating in sports, a growing rate of ligament rupture is evident. During ligament reconstruction, the ruptured ligament is removed and replaced with a graft to restore the knee to its pre-injured state. It has been found that sometimes instability persists after a successful surgery, which continues to be a matter of concern among surgeons. To gain a deeper understanding of why instability remains in these patients, we must improve our understanding of the role of knee ligaments and their contribution to knee stability. To date, numerous computational and experimental techniques have been used to analyze the effects of diseases, injuries, or different reconstruction methods on the stability of the knee joint; however, using purely computational or experimental techniques comes with some limitations. Therefore, in this thesis, we aimed to develop a combined experimental-computational technique to leverage the best aspects of both techniques. In this research, we designed virtual, computer-simulated ligaments whose behavior was similar to that of actual ligaments. We then replaced the native ligaments in the knee joints with virtual ones, allowing us to switch between different knee injury/repair conditions by turning off and on the virtual ligament. Developing a validated combined approach to study the knee joint would allow us to identify the role of ligaments in healthy joint biomechanics, examine the effects of diseases and injuries on joint stability, and identify the parameters that influence joint reconstructions. The ultimate impact of this research is to help researchers and surgeons assess surgical planning and care strategies.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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