Unicompartmental knee arthroplasty (UKA) in patients with isolated medial osteoarthritis of the knee is nowadays a standard procedure with good results, especially with the minimally-invasive approach. However, the survival rate of the unicompartmental knee prostheses is inferior to that of total knee prostheses. Therefore, further studying of UKA is still necessary. In most mobile bearing designs the femoral component has a spherical surface and therefore its positioning is not crucial. The role of the tibial slope in UKA has not been investigated so far. The manufacturers recommend tibial slopes with values between 10° positive slope and 5° negative slope. Most surgeons try to reconstruct the anatomical slope with a high failure by measuring the slope on x-rays. The aim of this study was to investigate the influence of the tibial slope on the wear rate of a medial UKA. In vitro wear simulation of medial mobile bearing unicompartmental knee prosthesis with a spherical femoral surface (Univation ®) was performed with a customized four-station servo-hydraulic knee wear simulator (EndoLab GmbH, Thansau, Germany) reproducing exactly the walking cycle as specified in ISO 14243–1:2002(E). The tibial tray was inserted with 2 different medial tibial slopes: 0°, 8° (n=3 for each group). The lateral tibial slope of the space-holder was not changed (0° for every group). We performed a total of 5 million cycles for every different slope, the gravimetric wear rate was determined gravimetrically using an analytical balance every 500 000 cycles according to the ISO 14243–2.Introduction
Materials and methods
