ALGORITHM FOR SEPTIC KNEE ARTHRODESIS: INDICATION – TECHNIQUES AND RESULTS

Abstract

Introduction: Knee arthrodesis is a well-recognized salvage procedure in patients with septic destruction of the knee joint. If fusion can be achieved, it offers the opportunity for a stable lower limb and eradication of infection, but at the expense of knee motion. However, knee arthrodesis in this setting may be difficult to achieve because of poor bone stock, persistent infection and soft tissue compromise. In this study we present clinical and radiological results after knee fusion as well as an algorithm according to different surgical techniques (hybrid external fixator (HEF), antegrad compression nail (ACN) and modular cement less titanium rod (MCR)) and types of soft tissue damages and bone loss caused by infection

Patients and Methods: Between 10/2000 and 10/2002 in 37 patients knee arthrodesis was indicated after septic joint destruction. In 23 Pat. (67.0 y, 19.4–88,8 y) septic failure of total knee arthroplasty (TKA)caused severe bone loss and soft tissue damage. Because solid bony fusion was not to be expected weight bearing capability was restored by the use of MCR in a second stage procedure, using a PMMA Gentamycin spacer for eradication. In 14 Pat. (54.3 y, 23.l–87.7 y) remaining bone stock indicated direct fusion. In 10 of these cases HEF was used (6x primary joint infection, 3x septic failure of TKA, lx infected osteosynthesis). 2 pat. denied written consent for HEF, another 2 pat. had infected ipsilaterale midshaft femor-and/or tibia non unions. Because of these we used the ACN.

Results: In 5 pat. (21.7%) treated with MCR 1,4 revision procedures were indicated to eradicate infection before the implantation of MCR. Recurrence of infection after implantation occurred in 13% (n=3): 2 pat. were treated non surgically, lx amputation had to be done. No radiological signs for implant loosening were seen. HEF was removed after 15 weeks (12–18w) on average. 5 revision procedures were necessary in HEF cases (lx Pin-, lx ring exchange, lx sequestrectomy after pintractinfection,)- hi 2 cases the procedure was changed to MCR because of a non-union. Using the ACN we saw a 100% fusion rate, in one case the sinus tract persisted. The check up examinations were done 8,7 month (2,4–22,4mo) after arthrodesis procedure. 82,6% of pat. after MCR, 100% after HEF- and ACN-had full weight bearing capability. Eradication of infection was achieved in 86,9% (n=20) after MCR, in 70% (n=7) after HEF and in 75% (n=3) after ACN. In all 3 groups soft tissue reconstruction by flap surgery was indicated in 20%.

Conclusion: HEF is indicated when bone loss allows bony fusion. Failure occurred when bone defects were underestimated ort he fixator was removed before the 14th week. MCR can be used when eradication of infection is success and because of bone defects direct fusion is not possible. When eradication is not possible and bone stock makes the fusion reliable the ACN can be used under ongoing infection. ACN is also used when HEF is not recommended by the patient or because of mechanical reasons (floating knee).