Intraoperative kinematics of the bicruciate retaining TKA using functional alignment and their influence on the clinical outcomes.

Background: Our surgical team has been performing bicruciate-retaining total knee arthroplasty (BCR-TKAs) with functional alignment (FA). This study aimed to investigate knee kinematics before and after FA BCR-TKA, as well as the influence of these changes on clinical outcomes.

Methods: Fifty cases of BCR-TKAs were included. Intraoperative rotational kinematics and anteroposterior translations between before (preinsertion group) and after (postinsertion group) BCR-TKA were compared. The relationship between clinical outcomes and intraoperative kinematic parameters between the two groups was evaluated.

Results: The tibial internal rotational angles of the preinsertion group were significantly larger than those of the postinsertion group at 0°, 60°, 90°, and maximum flexion angles. Anteroposterior (AP) translation of the femur center relative to the tibial center of the preinsertion group was significantly smaller than that of the postinsertion group at 60° and 90° of flexion angles. No difference was found between the two groups at 0°, 30°, and maximum flexion angle. A negative relationship was found between the difference in rotational angles at maximum flexion and knee injury, and osteoarthritis outcome score (KOOS) activity of daily living (ADL), and improvement of KOOS symptom and ADL subscale scores. A positive relationship was found between the difference in rotational angles at 0° and improvement of KOOS pain, sports, and quality of life subscale scores.

Conclusions: AP translation of the femur after BCR-TKA with respect to the tibia was similar to that of the preoperative knee. The change in rotational knee kinematics after BCR-TKA showed associations with clinical outcomes; however, the relationship remains multifactorial and should be interpreted with caution.