Interface stresses in the loosening of tibial components in total knee arthroplasties'

摘要

The design of prosthetic devices has a great influence on their mechanical response. The stability of the plate attached to the tibial component of the joint is one of the major considerations in total knee arthroplasty. this study focuses on the analysis of the mechanical behavior of two artificial knee devices. One post and two-post tibial components, each one made with steel and another of each made with polyethylene, were examined in regard to the pressure distributed along the prosthesis-bone interface. By applying the method of finite difference of a beam on an elastic foundation, a system of equations was developed and all pressures acting on the interface were analytically determined. A computer program was specially developed in order to perform all the calculations required for the determination of the unknown pressures. The experimental analysis at the interface of the tibial components involved the utilization of nitrile rubber transducers, which were used for recording the pressures distributed on each of the eight tibial specimens. These transducers were initially calibrated, and with the implementation of calibration curves the interface pressures were obtained. Theoretical and experimental results were compared, and pressure distribution curves were constructed for both designs and materials. It was found that for both designs the compressive pressures are maximum at the point were the load is applied. For the two-post tibial component however, the compressive pressures are distributed more evenly along the interface. In addition, the one-post tibial design produces maximum compressive and tensile pressures, while the percentage difference in pressure between the two designs varies depending on the load ratio and the distance from the load points.