Stereo Radiography of TKA Patella Mechanics

Study Overview
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Brief Summary
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The overall purpose is to compare the kinematics and mechanics of medialized dome and anatomic resurfacing through measurement and simulation, and to correlate these findings with patient satisfaction and performance. Aim 1: Comparison of patellofemoral kinematics between dome and anatomic implant designs using stereo radiography and correlation with patient function as measured by Knee injury and Osteoarthritis Outcome score, Knee Society score, and strength. Hypothesis: the anatomic patellar implant will have significantly greater sagittal flexion than the dome implant. Aim 2: Comparison of dome and anatomic moment arm, quadriceps efficiency, patellar contact mechanics and loading through the use of subject-specific simulation. Hypothesis: quadriceps efficiency and moment arm will be greater for the anatomic patellar implant, while loading between the patellar and femoral components will be reduced.

Detailed Description
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Successful function and outcome following total knee arthroplasty (TKA) is partly determined by the restoration of patellofemoral (PF) function and recovery of the quadriceps mechanism of the knee. Patients with TKA often exhibit adaptations in their movement patterns during functional activity that have been attributed to quadriceps strength reduction and activation deficits that may be linked to the mechanics of the reconstructed knee. Changes in the articular geometry with patella resurfacing also affect patellofemoral kinematics, contact mechanics and loading on the patellar bone. While movement adaptations persist in patients with TKA long after knee repair, measurement of the 6 degree-of-freedom (DOF) kinematics of the patellofemoral joint are difficult with traditional motion capture methods. High-speed stereo radiography (HSSR), an advancement of biplane fluoroscopy, enables measurement of bone and implant motion during activity with sub-mm accuracy. The ability to measure and model the kinematics of the knee with this precision can improve understanding of implanted knee mechanics. What's more, acquiring HSSR in synchrony with whole-body measurements (body segment video motion capture, muscle electromyography (EMG), and ground forces) establishes connections between joint-level and whole-body function, and enables creation of subject-specific models of the knee and lower extremity. Integration with modeling is important because it reveals the biomechanical consequences of differences in patellofemoral kinematics. Previous measurement and modeling comparisons of PF kinematics between dome and anatomic resurfacing designs have revealed differences in patellar sagittal plane flexion that have implications for quadriceps efficiency and patient satisfaction. Quadriceps efficiency is a measure of the effective moment arm of the quadriceps muscles; greater efficiency allows the quadriceps to produce knee extensor torque with less force. Patellar flexion can alter quadriceps efficiency by changing the moment arm of the patellar tendon and the way the patella transmits quadriceps force due to changes in patellofemoral contact. Patient satisfaction may be affected by changes in quadriceps efficiency through increased extensor mechanism strain and changes in load transfer that may be linked to anterior knee pain. While HSSR measurements can elucidate differences in dome and anatomic kinematics, computational modeling is required to determine how kinematic differences affect joint and muscle forces and overall limb functionality. Aim 1: Comparison of patellofemoral kinematics between dome and anatomic implant designs using stereo radiography and correlation with patient function as measured by Knee injury and Osteoarthritis Outcome score, Knee Society score, and strength. Laboratory measurements will be collected from 22 TKA patients with medialized dome and 22 TKA patients with medialized anatomic patellae. Equal numbers of men and women will be recruited for the study. The angle of the patellar component relative to the femoral component will be measured and compared to reported values in healthy subjects. Correlations will be made with patient outcome scores. Aim 2: Comparison of dome and anatomic moment arm, quadriceps efficiency, patellar contact mechanics and loading through the use of subject-specific simulation. Moment arm will be measured in millimeters as the distance from the patellar tendon to the knee joint center of rotation, and compared to values reported for the healthy knee. Quadriceps efficiency will be calculated as the ratio of quadriceps force to patellar tendon force. Patellar contact mechanics are defined as the force and location of force between the patellar and femoral components.

Official Title
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Influence of Patellar Geometry on Kinematics, Quadriceps Function, and Patient Outcome in Subjects With the Attune PS RP

Conditions
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Total Knee Arthroplasty

Intervention / Treatment
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* Device: DePuy Synthes Attune PS RP


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Men and Women Age: 18-80 years Unilateral or bilateral total knee replacement with an Attune posterior-stabilized rotating-platform implant including either medialized dome or medialized anatomic patellae Minimum 9 months post TKA procedure Exclusion Criteria: Concomitant lower extremity injury that continues to cause pain or loss of normal function (70 or greater Knee Society score) Inactive or unable to participate for health reasons (40 or greater on the physical component scale and and the mental component scale composite scores of the SF-12 Health Survey) Neurologic deficit that affects function or understanding of testing protocol Pregnant Other participation in a research study involving exposure to x-ray radiation body mass index greater than 30

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Medialized Dome Patella<br>Subjects with total knee arthroplasty using the DePuy Synthes Attune Posterior Stabilized Rotating Platform including patella resurfacing with a medialized dome component geometry | Device: DePuy Synthes Attune PS RP<br> <br> |
| Active Comparator: Anatomic Patella<br>Subjects with total knee arthroplasty using the DePuy Synthes Attune Posterior Stabilized Rotating Platform including patella resurfacing with an anatomic component geometry | Device: DePuy Synthes Attune PS RP<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Patellar Flexion Measured as the Relative Angle Between the Femoral and Patellar Components of the Implant. | Difference between dome and anatomic patellofemoral flexion, which is measured as the relative angle between the femoral and patellar components of the implant. | One day | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Replacement, Knee