Introduction: We studied from July 1997 infected hip and knee arthroplasties treated with only antimicrobial therapy without removal of the implants. The patients enrolled were not eligible for surgical operation or refused it. We tried to understand the role of this kind of therapy for the infections at stage I, II and III.

Material and Methods: We evaluated patients with hip or knee infected arthroplasties at stage I, II and III, respectively: an early infection (2–4 weeks after the prosthesis implantation), a chronic infection that appears more than one month after the operation and an hematogenous infection. The prosthetic hip infections were treated with an oral therapy for 6 months, while the prosthetic knee infections were treated for 9 months. Follow up examinations were conducted regularly for two years

Results: We observed 35 patients from July 1997: 15 with an infection at stage I, 17 at stage II: and 3 at stage III. In 23 patients the prosthesis affected was the hip, while in 12 patients it was the knee. The infections were due in most cases to Staphylococci (85.7%), while in 4 patients (3 cases of hematogenous infection) the pathogens isolated were Gram negative bacteria and 1 infection was due to Clostridium perfrigens. Only in 9 (25.6%) patients was performed a debridement before the beginning of the medical therapy. The overall success rate at one year of follow up was 72.7% (24/33), the success for the patients in stage I was 86.6%(13/15), in stage II 60% (9/15) and for stage III was 66.6% (2/3).

Conclusions: In patients with arthroplasty infection at stage I and III a long-term antimicrobial treatment, without the implant removal, could be a good chance, especially when the pathogen isolated is a S. aureus or a S. coagulase negative. As we expected the success rate for infection at stage II was the lower that we observed between all the prosthetic joint infection, treated with the only antimicrobial therapy. The gold standard for the treatment of stage II should be prosthesis revision (1 or 2 stages); but in our study we enrolled patients not eligible for surgical operation, because of severe clinical conditions, or patients that refused it. With these results we cannot recommend the medical therapy alone, but we can use it as a salvage therapy. As for the infections at stage I and III, no relapse had been observed after one year of follow up; we think that, especially for infections at stage II, a one-year follow up could be sufficient for the identification of the relapses.