Correct alignment in Total Knee Replacement

Correct alignment of the TKA implant is critical to restoring function and maximizinglongevity. TKA Malalignment is associated with early loosening, accelerated polywear,and increased pain.However, there are two schools of thought regarding the target of TKA implantation:1) Mechanical Axis Alignment and 2) Kinematic Axis Alignment (also referred to asAnatomic Alignment).1. MECHANICAL ALIGNMENTThe goal of TKA alignment is to restore the normal mechanical axis. This is notachieved however by attempting bone cuts that recreate the exact joint line betweentibia and femur, which would be °3 tibial varus and °3 femoral valgus in the nativeknee. Instead, both the distal femur and the tibia are cut to be perpendicular (°0) tothe mechanical axis.2. KINEMATIC ALIGNMENTSome surgeons think that mechanical axis is important, but restoring anatomicalignment around the knee is more important. They believe that all of the nonanatomiccuts made to the femur and tibia have a cumulatively detrimental impacton postop TKA function. Therefore, they cut the femur in °9 valgus and the tibia in °3varus to re-establish the normal joint line.