Introduction. Knee arthrodesis is a limb salvage procedure considered as an alternative to an amputation in case of severely infected total knee arthroplasties, associated with large damage of the extensor mechanism. The techniques are various and the series in the literature not always homogenous. In this study we assessed the results of knee arthrodesis performed with two monolateral external fixators in two perpendicular planes .

Material and methods . This retrospective series of 19 knee arthrodeses was done in 18 patients, which were 65 years old on average. All patients had severe damage on their extensor mechanism associated with an infection of their implant. In all cases the infection was documented and patients were treated by antibiotics during on average 9 months. The first surgical step consisted in a debridement of the knee which was provisionally fixated with the lateral external fixator. The second step consisted in the removal of the infected implant or of the spacer . The bony surfaces were freshened and the anterior external fixator was applied with a compressive effect on the fusion site . Full weight bearing was allowed 45 days after surgery.

Results. Radiological fusion was observed in 17 cases after 4,6 months on average and the external fixators were removed after 8 months on average. Two patients experienced wound healings problems that required additional plastic surgery. Two cases were revised and bone grafting was performed. One patient suffered from malunion at the last follow up ( 7 years in this study).

Discussion. This type of fixation avoids internal fixation in septic conditions. The transquadricipital pins of the anterior fixator are well tolerated. The rigidity of the combination of two monolateral fixators in two perpendicular planes allows quick reloading , which is essential in old patients, often debilitated by numerous procedures.

Conclusion. Arthrodesis is functionally an acceptable alternative to an amputation in these patients. This technique is reliable, has the advantage of avoiding an internal device in an infected knee, of stabilizing the fusion site thanks to the biplanar fixation and of allowing quick weight bearing,.