Kinematical analysis of a medial stabilized total knee arthroplasty during sit to stand and lunge: an in vivo dynamic RSA study
ESSKA Academy. Zaffagnini S. 11/08/19; 284377; epEKA-39 Topic: Biomechanics
Prof. Dr. Stefano Zaffagnini
Prof. Dr. Stefano Zaffagnini
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Kinematical analysis of a medial stabilized total knee arthroplasty during sit to stand and lunge: an in vivo dynamic RSA study

ePoster - epEKA-39

Topic: TKA

Marcheggiani Muccioli G.M.1, Alesi D.1, Roberti di Sarsina T.1, Cardinale U.2, Bontempi M.2, Zinno R.2, Di Paolo S.2, Bragonzoni L.2, Neri M.P.1, Zaffagnini S.1
1IRCCS Istituto Ortopedico Rizzoli, II Orthopaedic and Traumatologic Clinic, Bologna, Italy, 2Università di Bologna, Bologna, Italy

Introduction: A new model of medial stabilized (MS) total knee prosthesis has a high spherical congruence of the internal compartment which guarantees anteroposterior stability (AP) associated with a flat surface of the insert in the lateral compartment that allows a greater AP translation of the external condyle during knee flexion. The purpose of our study was to evaluate, by dynamic radiostereometric analysis (RSA), the in vivo kinematics of the knee after implantation of a mechanically aligned MS prosthesis during sit to stand and lunge movements.
Objectives: To evaluate the presence of medial pivot during knee flexion. We expected also that no significant differences would be present between the kinematics of the two examined tasks.
Aims: The aim of this study was to understand the effect of implant design and surgical technique on the kinematics of prosthetic knees during dynamic activities.
Methods: A cohort of 18 patients (72.1 ± 7.4 years old), after signing informed consent, was prospectively evaluated by dynamic RSA 9 months after surgery. The kinematic evaluation was carried out using the dynamic RSA tool, during the execution of sit to stand and lunge movements. The kinematic data were processed using the Grood and Suntay decomposition and the Low Point method.
Results: During the sit to stand the kinematic analysis showed the presence of a medial pivot, with a significantly greater (p=0.0216) anterior translation of the lateral condyle (3.9 ± 0.8 mm) than the medial one (1.6 ± 0.8 mm) associated with a femoral internal rotation (4.5 ± 0.9 deg). In the lunge, the lateral condyle showed a larger posterior translation with respect to the medial one (6.2 ± 0.8 mm vs 5.3 ± 0.8 mm) associated with a femoral external rotation (3.1 ± 0.9 deg) in the flexion phase, followed by a larger anterior translation of the lateral condyle respect to the medial one (5.8 ± 0.8 mm vs 4.6 ± 0.8 mm) associated with femoral internal rotation (6.2 ± 0.9 deg) in the extension phase. Analyzing individual kinematic, we found also a negative correlation between clinical scores and VV laxity during sit to stand (R= -0.61) and that the higher femoral extra-rotation, the poorer clinical scores (R= 0.65).
Conclusions: The MS prosthesis simulates in vivo the physiological kinematics of the knee described by Freeman and Pinskerova. It allows greater AP translation of the lateral compartment associated with a medial pivot during flexion in weightbearing conditions.
Kinematical analysis of a medial stabilized total knee arthroplasty during sit to stand and lunge: an in vivo dynamic RSA study

ePoster - epEKA-39

Topic: TKA

Marcheggiani Muccioli G.M.1, Alesi D.1, Roberti di Sarsina T.1, Cardinale U.2, Bontempi M.2, Zinno R.2, Di Paolo S.2, Bragonzoni L.2, Neri M.P.1, Zaffagnini S.1
1IRCCS Istituto Ortopedico Rizzoli, II Orthopaedic and Traumatologic Clinic, Bologna, Italy, 2Università di Bologna, Bologna, Italy

Introduction: A new model of medial stabilized (MS) total knee prosthesis has a high spherical congruence of the internal compartment which guarantees anteroposterior stability (AP) associated with a flat surface of the insert in the lateral compartment that allows a greater AP translation of the external condyle during knee flexion. The purpose of our study was to evaluate, by dynamic radiostereometric analysis (RSA), the in vivo kinematics of the knee after implantation of a mechanically aligned MS prosthesis during sit to stand and lunge movements.
Objectives: To evaluate the presence of medial pivot during knee flexion. We expected also that no significant differences would be present between the kinematics of the two examined tasks.
Aims: The aim of this study was to understand the effect of implant design and surgical technique on the kinematics of prosthetic knees during dynamic activities.
Methods: A cohort of 18 patients (72.1 ± 7.4 years old), after signing informed consent, was prospectively evaluated by dynamic RSA 9 months after surgery. The kinematic evaluation was carried out using the dynamic RSA tool, during the execution of sit to stand and lunge movements. The kinematic data were processed using the Grood and Suntay decomposition and the Low Point method.
Results: During the sit to stand the kinematic analysis showed the presence of a medial pivot, with a significantly greater (p=0.0216) anterior translation of the lateral condyle (3.9 ± 0.8 mm) than the medial one (1.6 ± 0.8 mm) associated with a femoral internal rotation (4.5 ± 0.9 deg). In the lunge, the lateral condyle showed a larger posterior translation with respect to the medial one (6.2 ± 0.8 mm vs 5.3 ± 0.8 mm) associated with a femoral external rotation (3.1 ± 0.9 deg) in the flexion phase, followed by a larger anterior translation of the lateral condyle respect to the medial one (5.8 ± 0.8 mm vs 4.6 ± 0.8 mm) associated with femoral internal rotation (6.2 ± 0.9 deg) in the extension phase. Analyzing individual kinematic, we found also a negative correlation between clinical scores and VV laxity during sit to stand (R= -0.61) and that the higher femoral extra-rotation, the poorer clinical scores (R= 0.65).
Conclusions: The MS prosthesis simulates in vivo the physiological kinematics of the knee described by Freeman and Pinskerova. It allows greater AP translation of the lateral compartment associated with a medial pivot during flexion in weightbearing conditions.
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