| Description |
Total knee arthroplasty (TKA) is the gold-standard treatment for degenerative and arthritic knee diseases. TKA replaces the damaged knee articular surfaces with a prosthetic knee joint composed of a metal femoral component and polyethylene tibial insert. In 2013, approximately 650,000 primary TKA procedures were performed in the U.S., with approximately 10% requiring revision surgery necessitated by the 10 - 15 years limited lifetime of the prosthetic knee joint. A major limiting factor to the longevity of a prosthetic knee joint is fatigue crack damage of the tibial insert. The objective of this work is to address the problem of fatigue crack damage through: (1) experimentally quantifying fatigue crack damage in polyethylene tibial inserts and (2) predicting fatigue crack damage through finite element modeling. We have developed a novel subsurface fatigue crack damage measurement method based on specimen transillumination and used this method to measure fatigue crack damage in two tibial inserts. We have also developed a dynamic finite element simulation of the stress in the tibial insert under knee simulator wear test conditions, for an entire gait cycle. Two polyethylene material models, linear elastic and linear viscoelastic, were compared. It was observed that choice of material model has a substantial effect on the maximum von Mises stress. The location of maximum von Mises, principal, and shear stress in the tibial insert were compared to the experimentally measured fatigue crack damage to determine whether the simulation accurately predicts fatigue crack damage in the tibial insert. It was observed that the von Mises stress alone is a poor predictor of fatigue crack damage, while the locations of maximum tensile principal stress and shear stress correspond closely to the locations where fatigue crack damage occurred. |
