The higher patient-reported outcome measure group had smaller external rotation of the femur in bicruciate-stabilized total knee arthroplasty

Purpose

The hypothesis of this study was that the kinematics of patients with higher patient-reported outcome measures (PROMs) differ from those of patients with lower PROMs after bicruciate-stabilized total knee arthroplasty (BCS-TKA).

Methods

A total of 32 patients with severe knee osteoarthritis were examined 11.2 ± 3.2 months after BCS-TKA. The patients performed squats under single fluoroscopic surveillance in the sagittal plane. To estimate the spatial position and orientation of the femoral and tibial components, a 2D-to-3D registration technique was used. This technique uses a contour-based registration algorithm, single-view fluoroscopic images and 3D computer-aided design models. Knee range of motion, varus–valgus alignment, axial rotation of the femur relative to the tibial component, anteroposterior translation of the medial and lateral femorotibial contact points, kinematic paths, and anterior and posterior post-cam engagement were measured. The patients were divided into two groups using hierarchical cluster analysis based on the 1-year postoperative Knee Injury and Osteoarthritis Outcome Score and 2011 Knee Society Score.

Results

The femoral component had significantly more external rotation in the low-score group than in the high-score group (5.1 ± 1.8° vs. 2.2 ± 2.7°, p = 0.02). The high-score group had a medial pivot pattern from 0 to 20° of flexion, without significant movement from 20 to 70°, and final bicondylar rollback beyond 70°. The low-score group had a medial pivot from 0 to 70° of flexion and bicondylar rollback beyond 70°. There were no significant between-group differences in the varus–valgus angle or post-cam engagement.

Conclusion

The higher PROM group had smaller external rotation of the femur after BCS-TKA.

Level of evidence

Level III.