Risk factors for subsequent debridement in pediatric patients with septic arthritis of the knee: A case control study

Background: Septic knee arthritis in pediatric patients is rare; however, timely diagnosis and treatment is key in preventing damage to articular cartilage and other structures in the joint. Risk and prognostic factors associated with treatment failure have not yet been studied in this patient population. In this study, we aim to assess how various lab and clinical findings at time of initial presentation associate with need for subsequent debridement among pediatric septic knee patients. Methods: This is a retrospective, single-center, case–control study comparing patients who did and did not receive subsequent irrigation and debridement for septic arthritis of the knee. Risk factors were assessed through univariate comparisons, utilizing chi-squared tests, t -tests, and Fisher-exact tests, as appropriate. Multivariate logistic regression and area under the receiver operating characteristic (AUROC) analysis was used to assess discriminatory ability of identified risk factors. Significance was defined as p < 0.05. Results: A total of 41 patients were included in this study, of which 18 underwent subsequent debridement. Patients requiring subsequent debridement had higher rates of positive blood culture (43.8% vs. 6.7%, p = 0.04), positive synovial cultures (66.7% vs. 26.1%, p = 0.01), and synovial white blood cell counts (WBC) > 100,000 cells/L (53.3% vs. 20.0%, p = 0.04). When these three variables were placed in a logistic model, an AUROC of 0.82 was observed (95% confidence interval: 0.64–0.99) Conclusions: Positive blood and synovial cultures, and synovial WBC > 100,000 cells/L, were identified as significant prognostic factors for subsequent septic knee surgery. Clinicians should consider these factors when counseling patients and caregivers about risk for subsequent debridement. Level of Evidence: III; Retrospective Case–Control Study.