INVESTIGATION ON THE EFFECTS INDUCED BY TKA FEATURES ON TIBIO-FEMORAL MECHANICS PART II: TIBIAL INSERT DESIGNS

Abstract

Posterior-stabilized (PS) prosthesis have been widely used in total knee arthroplasty (TKA) surgery during the last three decades generally reporting excellent results in long-term studies. Nevertheless, when the patient has nonstable knee envelope, it may require larger degree of restriction in order to manage knee instability. The Semi-constrained version of the PS prosthesis is then introduced, as primary or revision implant, enlarging the size of the post so as to be more restrictive. However, there is a lack of trust from surgeons in this last version based on the intuitive fear that its larger post could lead to higher forces and, therefore, to a premature failure of the post-cam mechanism of the prosthesis. To try to answer this question, the post-cam engagement of both designs have been studied under two daily activities, walking and squatting, by means of a finite element analysis (FEA). Kinematics and contact pressures have been evaluated in order to analyze the efforts supported by the prosthesis. The results obtained have shown a change on the kinematics especially along anterior–posterior (AP) direction as well as an increase of contact forces on the post of the semi-constrained design.