Infection after total knee replacement, which is a serious and expensive complication, often represent a diagnostic and therapeutic problem. The current incidence of infection after the primary procedure is 1 to 3%, depending on the published series. A correct and timely diagnosis, classification between early and delayed infection, and which microorganisms are involved, are crucial steps in defining prevention and treatment strategies.

Determination of the annual and three years incidence of infection after primary total knee replacement; evaluation of the microorganisms involved and its resistance patterns; assessment of treatment – surgical approach and selection of antibiotics.

Collection of clinical and laboratorial data of all patients who underwent primary total knee arthroplasty between 2011 and 2013 in our hospital; definition of periprosthesic infection cases following the Musculoskeletal Infection Society (MSIS) criteria.

During the study period, 526 primary knee replacements were performed in 521 patients; with 41 patients having bilateral replacements. The mean follow-up period was 30 months; 5 patients had no follow up and 1 died in the post operatory.

We reported 9 prosthetic infections, of which 2 did not reached the MSIS criteria, but were also considered based on high clinical suspicion. The majority of the cases (6) were delayed infections. The calculated 3 year incidence of infection after primary knee replacement was 1,6%, with annual rates of 3,0% (2011), 1,7% (2012) and 0,9% (2013). The microorganisms isolated were as follows: Staphylococcus aureus and coagulase-negative staphylococci, resistant to penicillin; Streptococcus agalactiae and one isolate of Serratia marcescens, both showing multiple antibiotic resistances.

Only one case was treated with surgical debridement and conservation of prosthesis, in the other 8 cases a two-stage implant revision procedure was performed. The antibiotics selected were vancomycin, fluoroquinolones and association of gentamicin and clindamycin.

Our local infection rates are in line with the published series from reference surgical centers. The annual incidence is decreasing, probably because the majority of our infection cases are delayed (recent years, shorter follow up period) and our preventive measures are improving. The microorganisms identified are also in agreement with published data, and our antibiotic resistance pattern is a valuable information to consider in a first empirical approach.

Treatment options suitable to each case, and antibiotic protocols need to be improved in our local practice. Preventive measures in delayed infections are still under debate, and represent another future challenge.

Introduction: Prosthetic joint infections are a growing burden. Since we felt that we were far from the optimistic results recently published, we decided to find out the reality in our department. The goals were to determine:

The rate of infections in primary and revision surgery (hip and knee)

Materials and Methods: We retrospectively reviewed clinical records of all patients that underwent surgical treatment due to infected hip or knee prosthetic joint between 1st July 2001 and 31st December 2007.

Results: Since the majority of infections (67%) presented in the first two years after surgery, we determined the rate of infections taking in to consideration a minimum two years follow-up. We calculated a 1.8% (12/678) rate of infection for primary total hip and 3.3% (20/588) for primary total knee arthroplasty. There was no statistically significant difference between the two groups. Revision hip surgery had a 5.4% (15/243) infection rate and revision knee surgery revealed an even higher rate of 10.3% (4/42). The difference between primary and revision surgery was statistically significant both for hip and knee.

Considering an infection free arthroplasty as the goal, the overall success rate of treatment was under 48% (30/69). The success of treating infections with debridement and retention of components was even lower (29%). Further analysis revealed a higher success of this approach (45%) when considering more appropriate candidates (short term infections). An interesting statistically significant difference was found favoring this approach in the knee.

Two-stage revision strategy was successful in achieving revision arthroplasty in 43% (20/46) of the cases. Most patients were never considered candidates to the second stage procedure. Knee joint and resistant microorganisms were found to be predictors of bad prognosis.

There was a 90% (18/20) survival rate of revision arthroplasties after two years average follow-up. There were only 2 cases of relapsing infection both controlled without prosthetic removal.

Conclusion: Our results compare poorly with the latest published data from different centers. They led us to implement new prophylactic measures as well as review our diagnostic and treatment options.