A comparative study of uncemented tibial components.

The effect of tibial component stem and post design on load distribution and on displacements at the component-bone interface was investigated. Four different configurations were tested with a flat component used as a control. Loading conditions included vertical central, vertical offset (eg, varus/valgus), shear and torque. Both artificial and cadaveric bones were used in the study. Pressure-sensitive film was used to obtain pressure patterns at the interface. Image processing was then used to quantify the load distribution. For shear and torque, relative motion was seen as a smeared pressure pattern. This was calibrated in terms of microns of displacement as a function of image density. The central stemmed and bladed designs performed better than short-pegged designs, in resistance to offset loading. In shear and torque, short pegs close to the component periphery, or a central stem with blades, produced the least interface displacement. The application of this work to the design of components for both press-fit and cemented application is discussed.