Stereo Radiography of TKA Patella Mechanics
Condition: Total Knee Arthroplasty
Study type: Interventional

Summary: 
      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: 
      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.
    

Intervention name(s): DePuy Synthes Attune PS RP
Intervention type(s): Device
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Replacement, Knee