Why does individualized TKA facilitate the restoration of native alignment?

Background: Traditional total knee arthroplasty (TKA) frequently utilizes systematic mechanical alignment and off-the-shelf (OTS) implants, which may not accommodate individual phenotypic variations. Recent shifts toward personalized alignment strategies highlight limitations in OTS designs, specifically regarding prosthetic overhang, ligamentous balancing, and the "trochlea dilemma," where patellofemoral tracking is compromised by fixed prosthetic geometry during kinematic alignment.

Objective: This article evaluates the technical rationale and clinical application of fully individualized TKA, focusing on the integration of 3D computed tomography (CT) planning and parametric implant design to restore patient-specific pre-arthritic anatomy.

Key Points: The manufacturing process utilizes 3D CT data of the hip, knee, and ankle to differentiate between native alignment and arthritic bone loss. A parametric model allows independent customization of femoral and tibial zones, facilitating the decoupling of patellofemoral and tibiofemoral kinematics. This approach addresses the mismatch between the prosthetic trochlear angle and the quadriceps line of force often observed in OTS implants. Surgical execution is guided by additive-manufactured patient-specific instruments. While the strategy aims to restore constitutional alignment, a "safe zone" is maintained, restricting tibial and femoral angles to 85°–95° and the hip-knee-ankle angle to 185°–193°. By replicating native joint surface radii and orientation, the requirement for intraoperative ligamentous release is minimized, potentially standardizing surgical technique through high-level personalization.

Conclusion: Individualized TKA components, designed through 3D modeling, allow for the restoration of pre-arthritic phenotypes while optimizing patellofemoral tracking. This comprehensive approach addresses the geometric limitations of conventional implants and supports the transition toward functional alignment strategies.