Reduced failure rate in knee prosthetic surgery with improved implantation technique.

From the Swedish Knee Arthroplasty project, started in 1975, types of relatively unmodified knee prostheses were chosen for analysis of time-dependent changes in the failure rate. One thousand nine hundred sixty-nine Marmor unicompartmental and 376 Total Condylar arthroplasties, all cemented, were followed until the end of 1989. The cumulative revision rates calculated with survival statistics showed a continuous improvement with time. The five-year revision rate was reduced from 11% to 5% for the Marmor prosthesis and from 10% to 2% for the Total Condylar prosthesis. This indicates that factors other than improved design are important. Such factors could include improved guide instruments, better surgical and cementing technique, influence of a learning curve, and patient selection.