Abstract
PurposeThe study aims were to assess the kinematic data, Internal-External (IE) rotation, and Antero-Posterior (AP) translation of the contact points between the femoral condyles and polyethylene insert and to develop a combined dynamic RSA-FE (Radiostereometric – Finite Element) model that gives results congruent with the literature.MethodsA cohort of 15 patients who underwent cemented cruciate-retaining highly congruent mobile-bearing total knee arthroplasty were analyzed during a sit-to-stand motor task. The kinematical data from Dynamic RSA were used as input for a patient-specific FE model to calculate condylar contact points between the femoral component and polyethylene insert.ResultsThe femoral component showed an overall range about 4 mm of AP translation during the whole motor task, and the majority of the movement was after 40° of flexion. Concerning the IE rotation, the femoral component started from an externally rotate position (− 6.7 ± 10°) at 80° of flexion and performed an internal rotation during the entire motor task. The overall range of the IE rotation was 8.2°.ConclusionsDuring the sit to stand, a slight anterior translation from 40° to 0° of flexion of the femoral component with respect to polyethylene insert, which could represent a paradoxical anterior translation. Despite a paradoxical anterior femoral translation was detected, the implants were found to be stable. Dynamic RSA and FE combined technique could provide information about prosthetic component’s stress and strain distribution and the influence of the different designs during the movement.
Highlights
Total knee arthroplasty (TKA) is the gold standard treatment for patients with primary osteoporosis, as it can relief pain and restore joint function
Dynamic Roentgen stereophotogrammetric analysis (RSA) allows to analyze in-vivo knee kinematics, it does not provide with the same accuracy the exactly contact points between the femoral condyles and polyethylene insert
An innovative technique, combining dynamic RSA and patient-specific finite element models, was applied to analyze a group of 15 patients who underwent total knee arthroplasty with a cemented Cruciate retaining (CR) highly congruent Mobile bearing (MB) TKA during the execution of a sit to stand from chair
Summary
Total knee arthroplasty (TKA) is the gold standard treatment for patients with primary osteoporosis, as it can relief pain and restore joint function. The prosthetic implant has a survival rate of 82% at 25 years [14]. A patient satisfaction about 80–90% after 1-5 years has been reported [5, 10]. The main causes of TKA failure and revision are infection, Model-based RSA is already used to assess in vivo knee kinematics in several prosthesis designs during daily life motor tasks [1, 7, 21, 27]. Dynamic RSA allows to analyze in-vivo knee kinematics, it does not provide with the same accuracy the exactly contact points between the femoral condyles and polyethylene insert. The kinematical data have been assessed frame by frame not considering the mechanical
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