Optimisation of the posterior stabilised tibial post for greater femoral rollback after total knee arthroplasty--a finite element analysis.

Femoral rollback after total knee arthroplasty (TKA) is necessary for flexion beyond 90-100 degrees. Femoral rollback in posterior cruciate substituting TKA occurs as a result of the interaction between the femoral cam and tibial post. The geometric design of the cam post mechanism determines the kinematics of rollback. The purpose of this study is to optimise the design of the femoral cam-tibial post articulation through finite element analysis and suggest various design parameters that would optimise femoral rollback. Modifications to the tibial post geometry without changing the relative post position or slope are made. Results are characterised in terms femoral rollback and pressure distribution at the tibial post. Small design modifications to the tibial post are seen to produce large changes in femoral rollback with relatively small accompanying increases in contact pressures at the tibial post.