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Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Medical Biophysics

Collaborative Specialization

Musculoskeletal Health Research

Supervisor

Teeter, Matthew G.

Abstract

Total knee arthroplasty (TKA) is the only solution for treating arthritis of the knee joint. Although it is successful at reducing pain and returning function to affected joints, one in five patients still report dissatisfaction following their operation. Bicruciate stabilized (BCS) TKA was developed to improve outcomes by replicating normal knee structure and function. The biomechanical, functional, and clinical outcomes for the BCS design were investigated in this thesis through radiographic imaging techniques, wearable sensor systems, and questionnaires in a cohort of TKA patients.

A stereo x-ray technique, called radiostereometric analysis (RSA), assesses implant fixation by tracking micromotion of TKA devices relative to the bone. Risk of implant loosening can be predicted based on the magnitude of these micromotions. This thesis found micromotion of the BCS TKA was within safe thresholds for both the gap balancing and measured resection techniques, indicating sufficient fixation to the bone occurs and the BCS TKA is not expected to have elevated revision risks due to implant loosening.

The exact cause of patient dissatisfaction after TKA is unknown. This thesis sought to find any differences in objective data between satisfied and dissatisfied patients with a BCS TKA. RSA was used to measure implant micromotion and tibiofemoral contact kinematics. A sensor system tracked measures of patient function during a timed-up-and-go functional test, and patient-reported outcomes were collected. We found no difference in implant micromotions or patient function between satisfied and dissatisfied patients. However, dissatisfied patients had more anterior contact on the lateral condyle of the knee in early flexion, and more pain and unmet expectations.

Finally, correlations were found between implant micromotion and tibiofemoral contact kinematics. Contact patterns indicating reduced posterior femoral rollback in the lateral compartment correlated with greater implant micromotion. Since BCS TKA aims to replicate normal knee kinematics and guide posterior rollback, it was concluded that undesired kinematics resulted in greater micromotions, and a greater risk of implant loosening.

Overall, the restoration of kinematics—particularly in the lateral compartment—in BCS TKA appears to be important for reducing implant migrations, improving pain and feeling in the knee, and ultimately, enhancing patient satisfaction.

Summary for Lay Audience

One in five Canadians live with arthritis, a disease of the joints that causes pain, limits mobility, and reduces quality of life. The knee is the most common joint affected, and with no cure available, many patients choose to undergo knee replacement to improve their symptoms. Knee replacements remove damaged bone and cartilage and replace them with metal and plastic implants. Although knee replacement is a very successful procedure, 20% of patients are dissatisfied after the operation. A relatively new type of knee replacement, called a bicruciate stabilized (BCS) implant, was designed to look and function like the normal knee to improve patient outcomes. In this thesis, the effectiveness of the BCS implant was studied.

The first step was to determine the fixation of BCS implants. Fixation is how securely the implants are attached to the bones and is measured by tracking how much the implant shifts, or migrates, after surgery. Implant migrations are very small, often less than a millimetre, and require special x-ray imaging, called radiostereometric analysis (RSA), to measure. Two surgical techniques were also compared; however, both techniques were determined to be equally effective options for long-term fixation of BCS implants.

Next, patients were divided into satisfied and dissatisfied groups to find any potential factors that cause patients to be dissatisfied with their knee replacement. RSA was used to study implant migration, and to assess kinematics (aka how the knee replacement moves) when bending the knee. Patient function was also measured during a walking and sitting test using sensors worn on each leg. Patients also answered questions about pain, expectations, and satisfaction. Dissatisfied patients were found to have different kinematics in the early stages of a knee bend, and reported more pain and unmet expectations.

Lastly, the implant migrations were compared with the kinematics to see if there were any relationships between the two for BCS implants. Abnormal kinematic patterns were related to greater implant migrations. This means that implants that do not move properly during knee bending are more likely to have worse fixation and may be at a greater risk of coming loose.

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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