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Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Biomedical Engineering

Collaborative Specialization

Musculoskeletal Health Research

Supervisor

Willing, Ryan

2nd Supervisor

Brent Lanting

Affiliation

London Health Sciences Center

Co-Supervisor

Abstract

Previous studies have demonstrated that satisfaction and revision rates following total knee arthroplasty (TKA) are lower than those of comparable surgeries such as total hip replacements. A leading cause for these revisions is joint instability which may be due to improper ligament balancing or poorly aligned surgical implants. One of the methods used to investigate biomechanical forces and kinematics is computational modelling of the post-operative TKA knee.

A unique knee model was used to investigate the biomechanical and kinematic effects of ligament model complexity, as well as the effects of simulating ligament wrapping versus ignoring ligament wrapping. We then used these ligament models to investigate the biomechanical effects of femoral implant malalignment. Our results show no discernable differences in kinematics due to ligament complexity or ligament wrapping except during specific loading scenarios. We also observed that an externally rotated femoral implant results in a more varus knee with lower medial collateral ligament tension compared to the TKA knee with a neutrally aligned femoral implant.

Summary for Lay Audience

Total knee replacement (TKR) surgery is a fairly common surgery in Canada, being performed over 70 000 times each year. TKR surgery is used as an end-stage treatment option for knee osteoarthritis which causes extreme joint pain and makes normal functional tasks such as walking and stair climbing a difficult ordeal for patients. Though it is typically successful at providing the patient with a pain-free knee, TKR satisfaction and revision rates remain lower than those of comparable surgeries such as total hip replacement surgery.

One of the leading causes for revision is joint instability following the initial TKR surgery. Instability may be caused by improperly balanced ligaments which leads to an imbalanced force distribution across the knee joint. Another cause of instability is poorly aligned implants. The femoral and tibial implants must be properly aligned to both each other, and their respective bones. A better understanding of both the biomechanical and the kinematic effects of malalignment could be key to improving patient outcomes.

We used a simulation software package for a novel application: constructing a virtual knee model that could conduct independent biomechanical analysis on knee motion without a physical joint motion simulator. This model was used to investigate the effects of femoral component malalignment on kinematics and ligament tensions during a variety of motions. We also looked at the effects of ligament model complexity and ligament model wrapping on the kinematics and ligament tensions of our TKR knee model.

Ligament model complexity had no discernible effect on kinematics of the TKR knee, however simulating ligament wrapping ensured that no unnatural motions occurred. This indicates that using simple ligament models may be a viable option during the computational modelling of the TKR knee. Analysis of femoral component malrotation demonstrated that a poorly aligned component can lead to a poorly aligned knee and results is different ligament tensions compared to a correctly aligned component.

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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