Der Effekt eines neuen Knochenzementes (Palamed G) auf das Migrationsverhalten der NexGen Knieendoprothese. Eine radiostereometrische Studie.

Migration of the tibial component in total knee arthroplasty (TKA) is subject of many studies using roentgen stereophotogrammetric analysis (RSA). In pioneer studies of cemented and uncemented tibial components, high migration values were found. Improvements in cementing technique, prosthetic design and pre-coating techniques could lower these values as shown in later-on studies. We investigated the effect of a high-viscosity bone cement on aseptic loosening of total knee endoprostheses using digital roentgen stereophotogrammetric analysis. 34 Patients were initially included in the study and operated between 12/1999 and 10/2000. All patients received a NexGen© TKA cemented into the proximal tibia using 40 g of a new high-viscosity bone cement with an early low-viscosity mixing-phase (Palamed G®, Merck, Germany). The implants and the tibial metaphysis were marked with standard tantalum markers. Biplanar radiostereometric analysis was performed post-operatively and after 3, 6, 12 and 24 months using a standard digital radiostereometric analysis setup (RSA Biomedicals®, Sweden). Endpoints were translation, rotation, maximum subsidence (MaxSub), maximum lift-off (MaxLiftOff) and maximum total point motion (MTPM). Quality criteria were: at least 3 corresponding tantalum markers in each examination, mean error < 0,25 mm and condition number < 110. Results were compared with historical data of the same design but using standard bone cement (Palacos R). Functional parameters were assessed using the Knee Society Score (KSS) clinical rating system. There were no complications and failures within the first two years. Except for anterior-posterior, medio-lateral stability and extension leg all endpoints of the KSS clinical rating system showed a significant improvement. After 24 months the usage of Palamed G® bone cement in total knee arthroplasty has demonstrated to be safe. Both the clinical and radiostereometric results were good and comparable to the results reported in other RSA studies in cemented total knee arthroplasty.