Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Surgery

Supervisor

Lanting, Brent

2nd Supervisor

Willing, Ryan

Co-Supervisor

Abstract

Total knee arthroplasty (TKA) continues to be a successful procedure for the past 50 years. We investigated the kinematics after under- and overstuffing the joint space with the polyethylene (PE) insert in both cruciate-retaining (CR) TKA and posterior-stabilized (PS) TKA. We compared CR and PS designs to evaluate their respective kinematic differences. This study employed a hybrid computational-experimental joint motion simulation on a 6 degrees of freedom joint motion simulator. Physical prototypes of a virtually performed TKA based on cadaveric CT scans and a virtual ligament model were utilized. We demonstrated understuffing decreases stability and the joint compressive forces, with the inverse occurring with overstuffing. In isolation, understuffing did not result in instability during activities of daily living in CR-TKA. Notably, a 2 mm increase or decrease in PE thickness altered the post-cam mechanism engagement. The PS design demonstrated greater stability, but overall, the kinematics between CR and PS designs were similar. This study demonstrates the ability of a hybrid model to further the understanding of kinematics in TKA.

Summary for Lay Audience

Total knee arthroplasty (TKA) continues to be a successful procedure for the past 50 years in treating patients with osteoarthritis of the knee. It entails resurfacing the joint surfaces of the knee with implants and a polyethylene (PE) insert which lies between them. We investigated the kinematics after under- and overstuffing the tibiofemoral joint space of the knee with the PE insert in both cruciate-retaining (CR) and posterior-stabilized (PS) designs of TKA. The under- and overstuffed joint spaces were simulated by 2mm with respective to a reference joint space. The CR design retains the posterior cruciate ligament (PCL), and the PS design substitutes the PCL with a post cam mechanism. We compared CR and PS designs to evaluate their respective kinematic differences. This study employed a hybrid computational-experimental joint motion simulation on a 6 degrees of freedom joint motion simulator machine. Physical prototypes of a virtually performed TKA based on cadaveric CT scans were mounted on to the joint motion simulator. A virtual ligament model developed from the literature was utilized and virtually installed around the TKA on the joint motion simulator. We demonstrated understuffing decreases stability by reducing the soft tissue tension and the joint compressive forces , with the inverse occurring with overstuffing the joint space with the PE insert. In isolation, understuffing did not result in instability during activities of daily living in CR-TKA. Notably, a 2 mm increase or decrease in PE thickness altered the post-cam mechanism engagement in PS-TKA. The PS design demonstrated greater stability, but overall, the kinematics between CR and PS designs were similar. This study demonstrates the ability of in vitro hybrid models to further the understanding of kinematics in TKA.

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