Abstract
There has been a renewed interest in the importance of achievement of a neutral, mechanical alignment in total knee arthroplasty (TKA). The purpose of this presentation is to argue the merits behind questioning a neutral, mechanical alignment following TKA, and why the concepts of “constitutional varus” and “kinematic alignment” deserve further investigation.
The impact of alignment on outcomes following TKA has been questioned for a number of reasons. First, recent investigations have highlighted that approximately 20% of patients are not satisfied with their outcome following TKA. Second, recent studies have shown that achievement of a mechanical axis within 3 degrees of neutral does not necessarily improve survivorship or clinical outcomes. Third, as patients requiring TKA have a wide array of morphologies and alignment, targeting the exact same alignment for each patient has been questioned. Lastly, despite the advent of new implant designs with proposed benefits of improved kinematics, few studies have shown a clinical improvement with their use.
The concept of “constitutional varus” has suggested that restoration of a neutral, mechanical alignment may not be desirable and unnatural as 32% of men and 17% of women have a natural mechanical alignment of greater than 3 degrees at skeletal maturity. The “kinematic alignment” technique focuses on restoration of the joint line of the distal femur, posterior femur, and tibia to those of the non-arthritic, native knee. The kinematic alignment technique has shown promising results. However, while these concepts have merit, questions still remain regarding the optimal alignment target for each, individual patient.
