Contact Characteristics of Anatomical and Symmetrical Unicompartmental Knee Prostheses

The development of artificial joints is now considered to be quite mature, and is the main treatment for osteoarthritis. However, in recent unicompartmental knee arthroplasty (UKA) clinical follow-ups, complications due to the wearing of polyethylene (PE) tibial components still exist. Therefore, this study is focused on avoiding and minimizing damage to the PE tibial component. Currently, the most common problem in the application of UKA is the malresection of the tibial plateau, often resulting in malpositioning of the tibial implant. This malpositioning may be the main reason for advanced wear and dislocation of the PE tibial component. In this study, in vitro test was used to study the stress change of malpositioned PE tibial components in order to better understand the damaging actions on PE tibial components. From in vitro test, it was found that anatomically designed unicompartmental knee prostheses (UKP) allowed more positional error in varus tilt than symmetrically designed UKP. Anatomical and symmetrical UKP should avoid any positional error greater than 5° and 10° valgus tilt respectively. Otherwise, increased wear of PE tibial components would result in shortened lifetime of the artificial joint.