In Vivo Kinematic Analysis of Bicruciate-Retaining Total Knee Arthroplasty Focused on Function of the Anterior Cruciate Ligament

Introduction: The utility of a bi-cruciate retaining total knee arthroplasty (BCR-TKA) is uncertain. This study aims to examine whether there is a difference in the kinematics of BCR-TKA and cruciate-retaining total knee arthroplasty (CR-TKA) with a shearing force on the anterior cruciate ligament (ACL). Methods: The subjects were 10 varus knees that underwent TKA (BCR: five knees, CR: five knees) at our hospital. We evaluated in vivo kinematics of the knee using fluoroscopy and investigated the femoral component translation relative to the tibial component from extension to maximum flexion, and the rotation angle between the components on level ground and a 10° forward slope. Results: The femoral component showed gradual external rotation relative to the tibial component with flexion. In the BCR group, the rotation across the flexion angles was larger and the medial and lateral nearest points were positioned more anterior with a statistical significance under both conditions. The kinematic pathway showed a medial pivot pattern in which the lateral nearest point translated posteriorly, whereas the medial nearest point stayed until 90° flexion in the BCR group. Conversely, in 0°-20° flexion, the component rotated internally and it showed a medal pivot pattern until 20°-90° in the CR group. Conclusions: There is a difference between the kinematics of BCR-TKA and CR-TKA. In the BCR group, kinematics close to screw home movement were found and these results provided evidence that conserved ACL function induced motion close to the normal knee, in comparison with CR-TKA.