Effect of femoral to tibial varus mismatch on the contact area of unicondylar knee prostheses

In unicondylar knee prostheses, the relative angle and congruency of the femoral against the tibial component is not mechanically constrained and may vary with the surgical implantation technique The contact area between both components was measured with increasing vat us (0-20 degrees) and flexion angles (-20 degrees to 90) in five prosthesis models in the laboratory The contact area varied with the relative position of the components and was critically reduced up to 70% at a yams range between >5 degrees and <25 degrees The importance of relative malpositioning of the femoral and tibial components may be underestimated and reduces the contact area of unicondylar piostheses decisively, independent from the limb axis This increases local pressure and may thus importantly contribute to increased wear and early loosening (c) 2009 Elsevier B.V All rights reserved