Is “symmetric” gap balancing still the gold standard in primary total knee arthroplasty?
A rectangular and symmetrical gap in flexion as well as in extension is mandatory to achieve good outcomes and good long-term results in total knee arthroplasty (TKA) using classical designs. Recently, as showed in several fluoroscopic studies, different modern designs (medial congruent or sagittally stable implants) have been demonstrated to better reproduce the more physiological medial pivoting (MP) biomechanics of the normal knee when compared to classical postero-stabilized (PS) and cruciate-retaining (CR) designs. These modern designs, characterized by different level of conformity, might require adopting a different surgical technique in terms of soft tissue balancing technique for primary TKA. In such cases, the current authors suggest to reproduce a slightly asymmetric extension and flexion gaps with a tighter medial then lateral compartment to re-establish the MP kinematics of the normal knee.