The influence of contemporary knee design on high flexion: a kinematic comparison with the normal knee.

Although Total Knee Arthroplasty (TKA) surgery enjoys 90% of outcomes with good to excellent results, some patients have difficulty adjusting their gait to accommodate the new articulations inherent in contemporary implant designs. Paradoxical motions inclusive of anterior sliding and lateral pivot are examples of aberrant TKA kinematics. This paper compares the motion of six contemporary TKA designs with recent in vivo kinematic data of the healthy un-operated knee through deep flexion1 by employing a computational kinematic simulator. Three designs employing tibial insert post and femoral cam motion control mechanisms were evaluated, Legacy LPS-Flex Fixed Bearing (Zimmer), Journey (Smith & Nephew), and Vanguard PS (Biomet), as well as three non post and cam designs, the MRK (Finsbury), Duracon and Triathlon (Stryker). All six designs are fixed plateau and currently available for clinical use in the United States.