Abstract
Polyethylene wear is one of the reasons for failure of total knee replacement (TKR). There are several reasons for wear, and the femoro-tibial contact area is an important factor. Mobile bearing, highly congruent prostheses might be more resistant to polyethylene wear than fixed bearing, incongruent prostheses. We evaluated the five- to eight-year experience of three university departments by using an original system with following highlights: implantation with a navigation system, extended congruency up to 90° of flexion, floating polyethylene component with non-limited movements of rotation, antero-posterior translation and medio-lateral translation.
347 patients have been operated on in the three participating departments with this new prosthesis system between 2001 and 2004, and have been prospectively followed with clinical and radiologic examination with a minimal follow-up time of five years. There were 246 women and 101 men, with a mean age of 67 years.
Clinical and functional results have been analyzed according to the Knee Society scoring system. Accuracy of implantation has been assessed on post-operative long leg antero-posterior and lateral X-rays. Survival rate up to eight years has been calculated according to Kaplan and Meier, with mechanical revision or any revision as end-points.
Complete patient history was obtained by 319 cases (92%). The mean clinical score was 93 points. The mean pain score was 47 points. The mean flexion angle was 118°. The mean functional score was 87 points. An optimal correction of the coronal femoro-tibial axis was obtained in 94% of the cases. Survival rate after eight years was 98.8% for mechanical revisions and 95.5% for all revisions.
We confirmed the influence of the navigation system on the accuracy of implantation. The clinical and functional results after five to eight years are in line with the better results of the current literature after conventional implantation of non-congruent prostheses. The survival rate is comparable to the current standards. The influence of the design on polyethylene wear will need a longer follow-up.
