[Knee arthrodesis with a double mono-bar external fixators to salvage infected knee arthroplasty: retrospective analysis of 18 knees with mean seven-year follow-up].

PURPOSE OF THE STUDY: Knee arthrodesis is sometimes the only alternative to amputation in patients with an infected knee prosthesis or in major bone damage with loss of the extensor system. We hypothesized that arthrodesis with a double mono-bar external fixators would be a valid technical solution enabling simple fixation sufficiently rigid to control infection. The main objective of our study was to assess outcome with this technique in terms of fusion. The secondary objective was to check remission of the infection at last follow-up for the infection cases.

MATERIAL AND METHODS: Mean follow-up in this retrospective analysis of 18 knee arthroplasties in 17 patients was 85 months. Mean patient age was 65 years. All patients presented destruction of the extensor system associated with infection on a total knee arthroplasty (n=14) or joint destruction (n=4). The first operative stage involved insertion of a temporary external fixator using a lateral bar to align the limb. The infected knee prosthesis was then removed or a spacer was inserted. After avivement of the bone surfaces, compression was applied with an external fixator using an anterior bar. Early weight bearing was encouraged. The lateral fixator was removed at 45 days and the anterior fixator at bone healing.

RESULTS: First-intention fusion was achieved in 16 of the 18 knees at mean five months (range 3-8 months). Fusion was achieved in one case after surgical revision using a bone autograft. Nonunion persisted in the other patient. Mean time to removal of the anterior fixator was 7.5 months (range 6-12 months). Remission of infection was noted at last follow-up in all patients with infection.

DISCUSSION: This technique provides effective treatment for infected knee prostheses or major joint destruction with loss of the extensor mechanism. Joint fusion limits function but is a better solution than above knee amputation. The rigid fixation achieved with two single-bar fixators positioned perpendicularly enables rapid weight bearing, a capital element for these often bedridden elderly patients with multiple co-morbidities. The essential element for fusion is a solid fixation. The use of external fixators also avoids implanting material in septic tissues. Associated with medical treatment for the infection we have been able to achieve complete remission of infection in all patients who underwent arthrodesis for an infected knee arthroplasty.