Prediction of TKR Function Using Specimen Specific Robotically Calibrated Knee Models

Abstract

Passive knee kinematics and kinetics following total knee replacement (TKR) are dependent on the topology of the component joint surfaces as well as the properties of the passive soft tissue structures (ligaments and capsule). Recently, explicit computer models have been used for the prediction of knee joint kinematics based on experimental investigations [1]. However, most of these models replicate experimental knee simulators [2], which simulate soft tissue structures using springs or elastomeric structures. New generations of experimental setups deploy industrial robots for measuring kinematics and kinetics in six degrees of freedom as well as the contribution of soft tissue structures. Based on these experiments, accurate soft tissue properties are available for use in computer models to aid more realistic predictions of kinematics. Final evidence of the quality of the kinematic predictions from these computer models can be provided by direct validation of the models against experimental data. Therefore, the objective of this study was to use in vitro robotic test data to develop, verify, and validate specimen specific virtual models suitable for predicting laxity and kinematics of the reconstructed knee.

Posterior stability in posterior-stabilized vs medially congruent total knee replacement: A radiological comparison of two polyethylene designs in a single model

“…Our findings in the MC group differ from the previous literature showing that, after sacrifice of the PCL, many TKA designs showed significant posterior tibial translation compared to normal knees. 32 The current authors justified this finding according to the specific more posterior dwell point on the MC insert when compared to CR and PS polyethylene (PE) designs 33 : in fact, in the kneeling x-ray, we could detect that the insert stays congruent with the medial femoral condyle in a more anterior position thanks to the 1/1 ratio between the J-curve shaped condyle and the fully congruent insert. In addition to this, even though the tibia and the baseplate showed a greater posterior draw when compared to PS, the MC insert might diminish the amount of shear forces on the PE and by that count avoid conflict between the elevated posterior lip of the insert and the posterior cortex of the femur during high flexion; it has also been demonstrated that more conforming surfaces could diminish the risk of degradation of the PE.…”