A Medial Pivot in Total Knee Arthroplasty is Driven by Soft Tissue Balance not Alignment – Results of a RCT

Objectives: In recent years an emphasis has been placed on trying to recreate the native knee medial pivot in total knee arthroplasty. Several studies have demonstrated improved outcomes in prostheses with asymmetrical flexion gaps mimicking native knee balance. The purpose of this study was to quantify prosthesis soft tissue balance and pivot patterns based on a kinematic (KA) or mechanical alignment (MA) surgical technique. Methods: A total of one hundred and nine primary cruciate retaining TKAs were randomised to either a mechanical or kinematic alignment technique. Medial and lateral compartmental pressures and contact pivot patterns were quantified at 10, 45 and 90 degrees of flexion using an insert pressure sensor (Verasense). Results: The primary driving factor for the pivot patterns was not alignment, but instead the differential pressure between the medial and lateral compartments at 45 and 90 degrees flexion (450 p