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.
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.
Study Type
OBSERVATIONAL
Enrollment
66
iTotal CR by Conformis
A standard knee replacement not using ConforMIS' iFit technology
Tennessee Orthopaedic Clinics
Knoxville, Tennessee, United States
University of Tennessee
Knoxville, Tennessee, United States
Kinematic Patterns during gait
There are multiple parameters captured by fluoroscopy that will be assessed during these 4 activities including: 1. Anterior/posterior medial and lateral condyle contact positions 2. Axial rotation of the femoral component relative to the tibial component 3. Condylar lift-off will be determined by measuring the distances from the medial and lateral condyles to the polyethylene insert surface 4. Weight-bearing range-of-motion.
Time frame: 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: 1. Anterior/posterior medial and lateral condyle contact positions 2. Axial rotation of the femoral component relative to the tibial component 3. Condylar lift-off will be determined by measuring the distances from the medial and lateral condyles to the polyethylene insert surface 4. Weight-bearing range-of-motion.
Time frame: 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: 1. Anterior/posterior medial and lateral condyle contact positions 2. Axial rotation of the femoral component relative to the tibial component 3. Condylar lift-off will be determined by measuring the distances from the medial and lateral condyles to the polyethylene insert surface 4. Weight-bearing range-of-motion.
Time frame: 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: 1. Anterior/posterior medial and lateral condyle contact positions 2. Axial rotation of the femoral component relative to the tibial component 3. Condylar lift-off will be determined by measuring the distances from the medial and lateral condyles to the polyethylene insert surface 4. Weight-bearing range-of-motion.
Time frame: at least 6 months post surgery
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