[Minimally invasive unicondylar knee replacement with computer navigation]

Abstract

Methods: From January 2003 to July 2005 a total of 50 St Georg medial knee monosleds with metal-backed tibial components in stably seated form and Uniglide prostheses (Alphanorm/Corin) with mobile bearing onlays were implanted in minimally invasive operations. Postoperatively the alignment-especially of the tibial components-was investigated, to check whether we had achieved the dorsal slope we had been aiming at, i.e. 5-7 degrees , in the region of these knee replacements.

Results: Before surgery there were initial malalignments of up to 10 degrees varus and 3 degrees valgus. All leg axes were restored to between -3 degrees and +3 degrees . The desired dorsal slope of 5-7 degrees for the knee monosleds relative to the tibial component was realized, the average slope being 5.3 degrees . The a-p alignment of the tibial component and of the femoral component was correct.

Conclusions: Use of the navigation system leads to more accurate and reproducible results in terms of tibial dorsal slope, which is extremely important when these monosleds are used. Overcorrection of the leg axis is generally avoided. The use of too-high medial onlays is also reliably avoided by the navigation system's monitoring of the level of the cut.