In Vivo Comparison of Knee Kinematics for Subjects Implanted With Either a ConforMIS or Traditional Knee Implant

Study Overview
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Brief Summary
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A better understanding of knee joint kinematics is important to explain the premature polyethylene wear failures within total knee arthroplasties (TKAs) and to help design a prosthesis that most closely approximates the normal knee. Previously, most experimental studies of knee kinematics have involved cadaveric, in vitro analyses, or have not tested the knee in a weight-bearing mode. Others have used exoskeletal linkages and skin markers that permit error due to undesired motions between markers and the underlying bone. More recently, fluoroscopy has been used to assess in vivo kinematics for subjects having a TKA. ConforMIS has attempted to follow a clearly different path than the major orthopaedic companies. They have chosen to offer patients a personalized knee implant based off of each patient's femoral and tibial bone geometry. The hypothesis is that these subjects will experience a more normal-like kinematic pattern, eliminating paradoxical anterior sliding during weight-bearing knee flexion. Therefore, the objective for this study is to analyze the in vivo kinematics for 25 patients implanted with a personalized ConforMIS TKA and 25 patients implanted with a traditional TKA design to determine if there are any kinematic differences between these TKA designs.

Detailed Description
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Each subject will be asked to perform five activities in one continuous sequence: (1) stand up from a chair, (2) walk up stairs, (3) walk down stairs, (4) level walking, and (5) a deep knee bend. Subjects will be video recorded from the waist down while performing the activities. The speed level of each trial will be based on the comfort level of the patient. The fluoroscopic images will be stored digitally for subsequent analysis on secure servers and workstations at the University of Tennessee.

Official Title
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In Vivo Determination & Comparison of Knee Kinematics for Subjects Implanted With Either a Personalized ConforMIS or Traditional Knee Implant

Conditions
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Complications; Arthroplasty

Intervention / Treatment
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* Device: Conformis CR Total Knee Replacement
* Device: Off the Shelf


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: At least 6 months post-op Between 40-70 years of age Body weight of less than 250lbs TKA patients will be judged clinically successful with an American Knee Society score of greater than 90 Must have post-op passive flexion of 100 degrees with no ligamentous laxity or pain Participants must be able to walk on level ground without aids and ascend/descend stairs without assistance. Subjects will either a ConforMIS™ TKA or a traditional TKA manufactured by any other orthopaedic company. Patients must be between 160cm (5'3) and 193cm (6'4) tall. Exclusion criteria: Subjects not willing to sign the Informed Consent and HIPAA forms to participate in the study BMI >40 Pregnant females Surgical procedures conducted within the past 6 months other than TKA Subjects from the physician's list who do not meet study requirements Unwilling or unable to comply with study requirements Participation in another clinical study which would confound results

Ages Eligible for Study
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Minimum Age: 40 Years
Maximum Age: 70 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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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| ConforMIS<br>Patients with ConforMIS implants | Device: Conformis CR Total Knee Replacement<br>* iTotal CR by Conformis<br>|
| Standard Total Knee Implant<br>Patients implanted with standard total knee implant | Device: Off the Shelf<br>* A standard knee replacement not using ConforMIS' iFit technology<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Kinematic Patterns during gait | There are multiple parameters captured by fluoroscopy that will be assessed during these 4 activities including: Anterior/posterior medial and lateral condyle contact positions Axial rotation of the femoral component relative to the tibial component Condylar lift-off will be determined by measuring the distances from the medial and lateral condyles to the polyethylene insert surface Weight-bearing range-of-motion. | at least 6 months post surgery | 
| Kinematic patterns during deep knee bend | There are multiple parameters captured by fluoroscopy that will be assessed during these 4 activities including: Anterior/posterior medial and lateral condyle contact positions Axial rotation of the femoral component relative to the tibial component Condylar lift-off will be determined by measuring the distances from the medial and lateral condyles to the polyethylene insert surface Weight-bearing range-of-motion. | at least 6 months post surgery | 
| Kinematics patterns during going up and down stairs | There are multiple parameters captured by fluoroscopy that will be assessed during these 4 activities including: Anterior/posterior medial and lateral condyle contact positions Axial rotation of the femoral component relative to the tibial component Condylar lift-off will be determined by measuring the distances from the medial and lateral condyles to the polyethylene insert surface Weight-bearing range-of-motion. | at least 6 months post surgery | 
| Kinematics patterns during getting up from chair | There are multiple parameters captured by fluoroscopy that will be assessed during these 4 activities including: Anterior/posterior medial and lateral condyle contact positions Axial rotation of the femoral component relative to the tibial component Condylar lift-off will be determined by measuring the distances from the medial and lateral condyles to the polyethylene insert surface Weight-bearing range-of-motion. | at least 6 months post surgery | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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kinematics, knee joint