DELAYED ONSET DEEP INFECTION AFTER TOTAL KNEE ARTHROPLASTY: COMPARISON BASED ON THE INFECTING ORGANISM

Abstract

The aim of our study is to identify the organisms causing delayed deep infections following primary total knee arthroplasty in the current situation. We also compared the differences in outcome based on the infecting organism.

We undertook a retrospective study of all the patients who presented with delayed deep infection following primary total knee replacement during a six year period between April 1998 and March 2004. We analysed the infecting organism, sensitivity of the organism to antibiotics, number of surgical procedure carried out and the outcome of the infected arthroplasty based on the infecting organism. Statistical analysis was done using Fisher’s Exact test for categorical data and Mann-Whitney U test for the non-parametric numeric data.

The mean age at the time of primary arthroplasty was 69.9 years (range 46 to 92 years, SD=10.8). The mean follow-up (time since the initial knee replacement) was 77.3 months (range 27–170 months,). The mean follow-up since the last surgical procedure to treat infection was 31 months (range 14–47 months). Organisms were isolated in 27 of the 31 patients who presented with delayed deep infection. Forty-four % of the organisms isolated were multi-drug resistant with increasing incidence of Methicillin resistant Staphylococcus aureus and multi-drug resistant Staphylococcus epidermidis infections. Successful outcome following an infected total knee arthroplasty was lower compared to the previous studies where there were fewer multi-drug resistant organisms. The number of patients with satisfactory outcome is significantly lower when the organism isolated is multi-drug resistant. Patients infected by multi-drug resistant organisms undergo higher number of surgical procedures compared to patients where the organism is not multi-drug resistant. We conclude that deep infection with MRSA and Methicillin resistant Staphylococcus epidermidis are on the rise. Outcome is significantly better when the organism isolated is non resistant Staphylococcus aureus.