The role of Implant Design and Soft Tissue Structures on CCK Knee Joint Stability

+*Wang, X; *Malik, A; *Padgett, DE; *Wright, TM *Hospital for Special Surgery, New York, NY +Weill Graduate School of Medical Science of Cornell University, New York, NY [email protected] INTRODUCTION Constrained condylar knee (CCK) implants are widely used in revision total knee arthroplasty (TKA) and, in recent years, increasingly in primary TKA, especially in the presence of functional loss of the collateral ligaments or severe joint deformity . In 2007, of 3058 TKAs performed at Hospital for Special Surgery, 450 were CCK implants. Shortand mid-term results show low failure rates, but complications include increased polyethylene wear and aseptic loosening. Both these complications could be caused by the increased constraint provided between the large, rectangular tibial post and the intercondylar femoral box. Little is known, however, about the relative constraint provided by post-box contact, by collateral ligaments, and by contact between the bearing surfaces of the tibial and femoral components. Such information would provide objective measures from which to determine the need for a CCK implant, would establish the role of soft tissue balancing, and would suggest design improvements to minimize mechanical complications while maximizing constraint. Thus, we sought to determine how load is shared between post-box contact, the tibiofemoral bearing surfaces, and the surrounding soft tissues.