The purpose of the following study was to present the general strategy for preserving the lower extremity by knee arthrodesis and to analyze the outcome of knee arthrodeses performed by a special modular system.

Between 2009 and 2014 35 knee arthrodeses were performed. 23 patients were male, 12 female. The average age was 66 years (42 to 83 years). The patients underwent an average of 6 operations because of infected knee arthroplasties previous to the knee arthrodesis. The main pathogen was S. epidermidis followed by MRSA. The arthrodeses system included a non cemented femoral and tibial stem (press fit application plus two static locking screws). These were connected by a special stem to stem clamp.

Immediate postoperative full weight-bearing was possible in 32 of 35 patients. We saw 4 recurrent infections (all connected to the patients, who did not show a full weight bearing after knee arthrodesis). In two cases re-revision surgery was successful and lead to a sufficient re-arthrodesis. In two cases above-knee-amputation was necessary. Peri-implant fractures were detected in 3 cases. All of them could be cured by changing the arthrodesis stem and to a longer one bridging the fracture. In one case a stem loosening was seen. This was as well addressed by the use of a longer stem.

Knee arthrodesis by a modular non cemented system is a god alternative in order to preserve the weight-bearing lower extremity. The complication rate is rather high due to the fact, that this procedure presents the final alternative to do so in patients, who are in extremis in terms of a long lasting aggressive peri-arthroplasty infection the lead to massive destruction of the soft tissue around the knee and a significant loss of function.