Predictors of failure after initial arthroscopic washout in septic arthritis of native knee joint- a retrospective analysis.

Background: Acute septic arthritis of the knee is an orthopaedic emergency requiring prompt debridement and washout to reduce infection. However, more than one washout procedure may be required to eradicate infection. This study was performed to analyse the factors associated with the failure of a single arthroscopic washout.

Methods: This is a retrospective analysis of 78 patients with septic arthritis of the knee over 6 years from January 2015 from a single trauma centre. We analysed the variables like patient demographic factors, comorbidities, laboratory parameters and various operative and non-operative factors with regard to the outcome after a single arthroscopic washout. Statistical analysis using univariate and multivariate logistic regression analysis were performed to identify the variables associated.

Results: Out of the 78 patients who underwent arthroscopic washout for a diagnosis of septic arthritis, 31 patients (39.74%) had failure of a single arthroscopic washout, with six patients (7.69%) requiring two additional washouts and one patient (1.28%) requiring three additional washouts to eradicate infection. Statistical analysis identified high temperature at presentation (p value 0.084), BMI >45 (p value 0.025), high CRP (0.014), high neutrophil count (p value 0.113) and high creatinine (p value 0.111) as the predictors of failure of a single arthroscopic washout.

Conclusion: A high failure rate (39.74%) was seen with a single arthroscopic washout procedure. A high BMI, elevated CRP, higher temperature at presentation, elevated neutrophil count were identified as the predictors of failure of a single arthroscopic washout for septic arthritis of the knee in our study.