Does a minimally invasive approach affect positioning of components in unicompartmental knee arthroplasty? Early results with survivorship analysis.

Fifty unicompartmental knee arthroplasties (UKAs) were performed through a minimally invasive approach and were reviewed with an average follow-up of 3.7 years. This technique leads to reduced access to surgical landmarks. The purpose of this study was to evaluate whether correct component positioning is possible through this less invasive approach. Component positioning, femorotibial alignment and early outcomes were evaluated. We observed perfect tibial component position, but femoral component position was less consistent, especially in the sagittal plane. Femorotibial alignment in the coronal plane was within 2.5 degrees of the desired axis for 80% of the cases. Femoral component position in the sagittal plane was within a 10 degrees range of the ideal for 70% of the cases. The mean IKS Knee Function Score and Knee Score were 89/100 and 91/100 respectively. We observed two polyethylene dislocations, and one revision was performed for progressive patellofemoral arthrosis. According to our data, minimally invasive UKA does not conflict with component positioning although a learning curve needs to be respected, with femoral component positioning as the major obstacle.