LAUSR

Background: The purpose of this study is to identify risk factors associated with repeat surgical irrigation in pediatric septic hip arthritis. Methods: A single center retrospective case-control study was performed. Patients who underwent ≥2 washouts (cases) were compared with those who had only 1 washout (controls). Demographic, clinical, laboratory, microbial, and magnetic resonance imaging data were compared between cases and controls and a prediction model was developed using logistic regression. A risk score was then constructed by counting the number of risk factors from the model that were present in each patient. Results: We identified 26 patients between 1994 and 2015 who underwent ≥2 washouts for septic hip arthritis, and 63 control patients who had only a single washout. Twenty-two patients had 2 washouts, 3 had 4 washouts, 1 had 5 washouts. Median number of days between first and second washout was 5 (interquartile range, 4 to 8). The most common reason for repeat washout was persistent fever (N=21), followed by persistently elevated laboratory values (N=13), abnormal magnetic resonance imaging findings (N=12), and continued pain (N=12). Repeat washout cases demonstrated higher temperature preoperatively (P<0.001), had more frequent initial misdiagnosis (P=0.002), and had a longer time from symptom onset to surgery (P=0.02). Laboratory values in these cases showed higher C-reactive protein (P=0.003), and more frequent left shift (P=0.03) at presentation, with a greater proportion of positive cultures (P<0.001). Postoperatively, repeat washout cases had higher temperatures (P<0.001), more frequent wound drainage (P=0.02), and complications (P=0.001). A risk score for predicting the likelihood of undergoing repeat washout was constructed by counting the number of the following factors present: presence of left shift in CBC, positive blood or synovial fluid cultures, and postoperative temperature over 39°C. Seventy percent of cases had ≥2 of these risk factors and 80% of controls had ≤1 risk factor. Conclusions: Cases of pediatric septic arthritis which undergo repeat washout are associated with left shift, high postoperative temperatures, and positive cultures. They have more frequent misdiagnosis leading to delayed treatment and subsequent medical complications. Level of Evidence: Level III.