Does Component Alignment Affect Patient Reported Outcomes following Bicruciate Retaining Total Knee Arthroplasty? An In Vivo Three-Dimensional Analysis.

This is an experimental study. Anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) retaining bicruciate retaining (BCR) total knee arthroplasty (TKA) have the potential to restore normal knee kinematics and thus improve patient outcome. Limited studies have examined the relationship between component alignment and patient-reported outcome measures (PROM). This study aims to determine (1) accurate three-dimensional (3D) component alignment of BCR TKA and (2) whether the component alignment of BCR TKA affects PROMs. The 3D modeling analysis was performed based on computed tomography images from 29 BCR TKAs. Component orientations were quantified for femoral and tibial components in the sagittal, axial, and coronal planes. The knee society scores (KSS) were collected preoperatively and postoperatively at 1-year follow-up. Multiple comparisons were performed to analyze the relationship between component alignment and patient outcomes. High variability was observed in the tibial component alignment (root-mean-square values: axial plane 6.6 degrees, sagittal plane 5.1 degrees, and coronal plane 4.0 degrees). At 1-year follow-up, significant improvement in KSS was noted in BCR TKA patients ( < 0.001). However, regression analysis adjusting for baseline KSS demonstrated the postoperative KSS was negatively associated with the posterior tibial slope (B [slope of the output of the regression analysis] = 2.597,  = 0.006). Patients with greater posterior tibial slopes were reported poorer postoperative functions at 1-year follow-up. Excessive posterior tibial slope may generate greater posterior force on the femur that leads to continuous overloading of the preserved ACL, suggesting optimal sagittal plane alignment of the tibial component may be important for the optimization of postoperative functions of BCR TKA patients.