Repeat irrigation & debridement for patients with acute septic knee arthritis: Incidence and risk factors

Septic knee arthritis is considered an orthopedic emergency due to its significant morbidity and potential to be life-threatening. One important outcome in treatment of septic knee arthritis is whether return to the operating room for repeat irrigation and debridement is required. This complication presents extra burden to the patient, as well as to the health care system. This study aims to first isolate the incidence of repeat irrigation and debridement at the authors' home institution and then define risk factors for repeat washout for septic arthritis of the knee.

Records from all patients at a single academic institution with acute septic knee arthritis who had arthroscopic or open I&D of the knee joint from January 2005-December 2015 were collected retrospectively. Patients were initially identified on the basis of diagnosis coding in the institution's medical information system. Following collection/screening based on strict inclusion/exclusion criteria, a cohort of 63 patients was ultimately included. 18 patients were assigned to a "repeat washout" (RW) cohort and 45 patients were assigned to a "no repeat washout" (NRW) cohort. Univariate analyses and multivariable regression models were performed between the two washout cohorts to identify variables associated with repeat washout.

Patients requiring a repeat washout (RW) had a statistically significant association with African American/Hispanic race, higher BUN levels, higher serum white blood cell (WBC) count on admission, concurrent infection, and isolated bacteremia when compared to those patients who did not require a repeat washout (NRW) (all respective P < 0.05). Multivariable regression analysis demonstrated concurrent infection and higher synovium WBC count to increase the risk for another repeat washout. Patients who had a concurrent infection were shown to have nearly 12-fold higher odds of needing a repeat washout than those without a concurrent infection (95% CI:2.40-56.88; P = 0.0023). For every 1000 unit increase in synovium WBC count, the odds of needing a repeat washout increased by 1% in patients with concurrent infection (95% CI:1-2%; P = 0.0168).

This study retrospectively isolated risk factors associated with repeat surgical lavage. In the multivariable regression analysis, both concurrent infection and increased synovial WBC count were significantly associated with the need for repeat knee I&D. This finding is significant, as it may signify a potential for increased infectious resilience for acute septic arthritis of the knee secondary to seeding from systemic infection, thus requiring multiple I&Ds to meet resolution. This finding may carry clinical significance in the early stages of patient counseling regarding hospital course and prognosis.

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