Effect of patella button design on modulating rotating hinge knee implant biomechanics

Open Access
- Author:
- Gonzalez, Rebecca
- Area of Honors:
- Kinesiology
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Stephen Piazza, Thesis Supervisor
Lacy Marie Alexander, Thesis Honors Advisor - Keywords:
- total knee arthroplasty
patellar resurfacing
patella
anatomical patellar implant
spherical patellar implant
knee joint biomechanics - Abstract:
- Patellar resurfacing in total knee arthroplasty has been a controversial topic when it comes to when to do it and with which patellar implant design. This controversy continues as little attention is given to patellofemoral implant biomechanics in research compared to femoral and tibial implant biomechanics. With contradictory findings on the benefits and risks of patellar resurfacing, it is still unclear as to what decision is considered best when debating whether to resurface the patella in total knee arthroplasty. If an orthopedic surgeon decides to resurface the patella, further decision-making is needed to decide on the patellar implant design. Past studies have noted differences between anatomical-type and spherical-type patellar buttons. This study aims to address differences between those patellar implant designs while assessing the repeatability of the Penn State Knee Simulator in the Penn State Biomechanics Laboratory to provide the basis for repeatable and reliable results while assessing inter-trial repeatability that has not been reported previously in similar “Oxford rigs”. Thirty-two trials of an ultra-high-molecular-weight polyethylene spherical patella button were used to assess simulator repeatability. Thirty-eight trials of the spherical patella button (thirty-two made from ultra-high-molecular-weight polyethylene and six 3D printed) and eight trials of the anatomical patella button (3D printed) were tested. The knee simulator performed knee extension. Load cell force and motion capture data were collected to analyze differences in quadriceps force, patellofemoral force, patellar tendon force, tibiopatellar angle, effective quadriceps moment arm, patellar tendon moment arm, and patellar tilt at 90° of deep knee flexion and differences in medial patellar shifting throughout the extension cycle between the anatomical and spherical designs. The anatomical patella experienced less patellar tilt and more medial patellar shifting than the spherical patella throughout the extension cycle. The anatomical patella was also more medially tilted at 90° of knee flexion compared to the spherical patella. These findings, along with other findings from this study, will contribute to the body of research that helps orthopedic surgeons make informed decisions about patellar resurfacing in total knee arthroplasty. This work is important because the biomechanical and kinematic function of the patellofemoral joint is essential in performing daily activities that require loaded knee flexion and extension.