Minimally invasive unicompartmental knee prosthesis implantation with a non-image based navigation system

摘要

Objectives: We hypothesized that the used non image based navigation system will allow placing a unicompartmental knee prosthesis (UKP) in an optimal position with a minimal invasive approach. Background: The accuracy of implantation is an accepted prognostic factor for the long term survival of a UKP [1, 2, 4]. Minimal invasive technique is recommended for faster post-operative recovery, but its accuracy is questionable. Computer assisted systems have been developed for TKP implantation [3], and have shown to allow a higher precision of implantation for such implants in comparison to conventional instruments. We developed an adaptation of the OrthoPilot non image based system for either conventional or minimal invasive UKP implantation [5]. Design/Methods: Three infrared localizers are fixed in the distal femur, the proximal tibia and the foot, and their relative motion is tracked by an infrared camera. The software calculates the respective centers of rotation of the hip, knee and ankle joints. A localizer is then fixed on the tibial or femoral resection blocks, and the software displays on line the orientation of this block in comparison to the mechanical axes of the bone. The surgeon can fix the block with the desired orientation before performing the bony resection. For minimal invasive technique, resection blocks were modified to allow the whole procedure through an 8cm antero-medial skin incision. 20 patients were operated on for medial unicompartmental knee osteoarthritis with this experimental minimal invasive navigated technique (group A). Radiological quality of implantation was compared to a matched-paired group of 20 cases operated with the conventional navigated technique (group B). Results: The coronal mechanical femoro-tibial angle was within the desired range in 16 cases in group A and 17 cases in group B. The femoral component was optimally implanted in 17 cases in group A and 18 cases in group B. The tibial component was optimally implanted in all cases. Mean length of the skin incision was 8cm (range 7 to 10cm) in group A. There was no significant difference between both groups.