Kinematically Aligned Total Knee Arthroplasty with Patient-Specific Instrument.

Kinematically aligned total knee arthroplasty (TKA) is a new alignment technique. Kinematic alignment corrects arthritic deformity to the patient's constitutional alignment in order to position the femoral and tibial components, as well as to restore the knee's natural tibial-femoral articular surface, alignment, and natural laxity. Kinematic knee motion moves around a single flexion-extension axis of the distal femur, passing through the center of cylindrically shaped posterior femoral condyles. Since it can be difficult to locate cylindrical axis with conventional instrument, patient-specific instrument (PSI) is used to align the kinematic axes. PSI was recently introduced as a new technology with the goal of improving the accuracy of operative technique, avoiding practical issues related to the complexity of navigation and robotic system, such as the costs and higher number of personnel required. There are several limitations to implement the kinematically aligned TKA with the implant for mechanical alignment. Therefore, it is important to design an implant with the optimal shape for restoring natural knee kinematics that might improve patient-reported satisfaction and function.