Knee kinematics after cruciate retaining highly congruent mobile bearing total knee arthroplasty: an in vivo dynamic RSA study
ESSKA Academy. Zaffagnini S. 11/08/19; 284376; epEKA-38 Topic: Biomechanics
Prof. Dr. Stefano Zaffagnini
Prof. Dr. Stefano Zaffagnini
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Knee kinematics after cruciate retaining highly congruent mobile bearing total knee arthroplasty: an in vivo dynamic RSA study

ePoster - epEKA-38

Topic: TKA

Bragonzoni L.1, Marcheggiani Muccioli G.M.2, Cardinale U.1, Bontempi M.1, Alesi D.2, Roberti di Sarsina T.2, Lo Presti M.2, Iacono F.3, Zaffagnini S.2
1Università di Bologna, Bologna, Italy, 2IRCCS Istituto Ortopedico Rizzoli, II Orthopaedic and Traumatologic Clinic, Bologna, Italy, 3Humanitas Clinical and Research Center, Department of Biomedical Sciences, Humanitas University, Rozzano, Italy

Introduction: Cruciate-retaining total knee arthroplasty (CR-TKA) is one of the principal techniques used to replace the osteoarthritic knee joint. This work presents a kinematic evaluation of a CR highly congruent Mobile Bearing TKA design using dynamic Roentgen Sterephotogrammetric Analysis (RSA). The purpose of this study is to better understand the in vivo kinematics of knee joint after the implantation of this prosthetic model.
Objectives: To assess the in vivo kinematics of a posterior CR highly congruent mobile bearing (MB) TKA design during a sit-to-stand movement using model-based dynamic RSA.
Aims: The aim of this study is to understand the effect of implant design and surgical technique on the kinematics of prosthetic knees during dynamic activities. This will allow improving prosthesis designs on the basis of objective in vivo functional data.
Methods: This study obtained the approval from Institutional Review Board (IRB) of Rizzoli Orthopedic Institute. A cohort of 15 patients, after signing informed consent, was prospectively evaluated 9 months after implantation of a CR-TKA. The mean age of patients was 74.8 (range 66-85) years. The patients were asked to perform a sit-to stand motor task: from the sitting position, the patient had to stand up according to his possibilities. Bi-planar radiographs were acquired at 8 frames per second using a RSA tool and data were evaluated using the Grood and Suntay decomposition and the Low-Point methods.
Results: Kinematical results showed that from 80° knee flexion to maximum extension, an anterior femoral translation was observed (from -4.9 ± 0.2 mm to 0.5 ± 0.2 mm). During the motor task, the position of the medial condyle moved from 12.0 ± 0.2 mm at 80° of flexion to -12.4 ± 0.2 mm at 5° of flexion; the position of the lateral condyle moved from 8.1 ± 0.2 mm at 80° of flexion to -12.4 ± 0.2 mm at 5° of flexion, defining a bi-condylar rollback where both condyles moved parallel backward. During the whole movement, an internal rotation of the femoral component was observed (from -11.3 ± 0.2° to -5.1 ± 0.2°).
Conclusions: The most important finding of the present study is that the observed kinematics differ from that of the normal knee in several expects. During the movement we observed a bi-condylar rollback where both condyles moved parallel backward. The debate is still open and further investigations are in progress.
Knee kinematics after cruciate retaining highly congruent mobile bearing total knee arthroplasty: an in vivo dynamic RSA study

ePoster - epEKA-38

Topic: TKA

Bragonzoni L.1, Marcheggiani Muccioli G.M.2, Cardinale U.1, Bontempi M.1, Alesi D.2, Roberti di Sarsina T.2, Lo Presti M.2, Iacono F.3, Zaffagnini S.2
1Università di Bologna, Bologna, Italy, 2IRCCS Istituto Ortopedico Rizzoli, II Orthopaedic and Traumatologic Clinic, Bologna, Italy, 3Humanitas Clinical and Research Center, Department of Biomedical Sciences, Humanitas University, Rozzano, Italy

Introduction: Cruciate-retaining total knee arthroplasty (CR-TKA) is one of the principal techniques used to replace the osteoarthritic knee joint. This work presents a kinematic evaluation of a CR highly congruent Mobile Bearing TKA design using dynamic Roentgen Sterephotogrammetric Analysis (RSA). The purpose of this study is to better understand the in vivo kinematics of knee joint after the implantation of this prosthetic model.
Objectives: To assess the in vivo kinematics of a posterior CR highly congruent mobile bearing (MB) TKA design during a sit-to-stand movement using model-based dynamic RSA.
Aims: The aim of this study is to understand the effect of implant design and surgical technique on the kinematics of prosthetic knees during dynamic activities. This will allow improving prosthesis designs on the basis of objective in vivo functional data.
Methods: This study obtained the approval from Institutional Review Board (IRB) of Rizzoli Orthopedic Institute. A cohort of 15 patients, after signing informed consent, was prospectively evaluated 9 months after implantation of a CR-TKA. The mean age of patients was 74.8 (range 66-85) years. The patients were asked to perform a sit-to stand motor task: from the sitting position, the patient had to stand up according to his possibilities. Bi-planar radiographs were acquired at 8 frames per second using a RSA tool and data were evaluated using the Grood and Suntay decomposition and the Low-Point methods.
Results: Kinematical results showed that from 80° knee flexion to maximum extension, an anterior femoral translation was observed (from -4.9 ± 0.2 mm to 0.5 ± 0.2 mm). During the motor task, the position of the medial condyle moved from 12.0 ± 0.2 mm at 80° of flexion to -12.4 ± 0.2 mm at 5° of flexion; the position of the lateral condyle moved from 8.1 ± 0.2 mm at 80° of flexion to -12.4 ± 0.2 mm at 5° of flexion, defining a bi-condylar rollback where both condyles moved parallel backward. During the whole movement, an internal rotation of the femoral component was observed (from -11.3 ± 0.2° to -5.1 ± 0.2°).
Conclusions: The most important finding of the present study is that the observed kinematics differ from that of the normal knee in several expects. During the movement we observed a bi-condylar rollback where both condyles moved parallel backward. The debate is still open and further investigations are in progress.
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