Background/Purpose:

Delays in diagnosis and treatment of septic arthritis may be associated with significant morbidity. While many patients with suspected or proven septic arthritis are treated surgically, aggressive surgical intervention may be unnecessary when the diagnosis is not secure. This includes patients with negative synovial fluid cultures, representing up to 40% of patients with clinically suspected septic arthritis. We aim to characterize patients with presumed septic arthritis who were treated surgically, but who had negative synovial fluid cultures. This may help predict which patients could be treated safely without surgical intervention.

Methods:

We conducted a restrospective cohort study of patients 18 years and older admitted to a single tertiary care center from January 2010 to May 2014 with a presumptive diagnosis of septic arthritis leading to operative management. Patients were stratified into culture-positive and culture-negative groups based on synovial fluid testing. Length of hospital stay (LOHS) was designated as the primary outcome. Secondary outcomes included 60 ̵ day readmission rate and establishment of an alternative diagnosis to explain the index admission within a year of discharge.

Results:

Of 208 patients with clinically suspected septic arthritis who underwent surgical intervention, 90 (43.3%) were synovial fluid culture ̵positive. The culture ̵ positive and culture ̵ negative groups were similar with respect to gender (approximately half were female), age (mean of 63 years), frequency of prosthetic joint involvement (about 60%), and frequency of knee involvement (about 60%). For the culture-positive group, mean LOHS and 60 ̵ day readmission rate were 11.4 days and 26.7%, respectively; in the culture-negative group, mean LOHS and 60-day readmission rate were 9.9 days and 36.4%, respectively (p = 0.09 for LOHS; p = 0.18 for 60-day readmission rate). An alternative diagnosis to explain the index admission was made in 3 (3.3%) cases in the culture ̵positive group and in 10 (9.3%) cases in the culture ̵ negative group (p = 0.16). Among patients with native joints, mean LOHS, 60-day readmission rate, and frequency of alternative diagnosis did not differ significantly between the culture ̵ positive and culture ̵ negative groups.

Conclusion:

In our medical center, the majority of patients with clinically suspected septic arthritis managed operatively had negative synovial fluid cultures at the time of diagnosis. While those with positive and negative synovial fluid cultures had similar baseline features, we observed a trend toward shorter length of hospital stay and more alternative diagnoses in the culture-negative group. The inclusion of additional presenting features (currently underway), including the presence of comorbidities, prior use of antibiotics, systemic signs of infection, and synovial fluid characteristics, may identify a subset of patients with suspected septic arthritis who may be managed safely without surgery.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-characteristics-and-outcomes-in-synovial-fluid-culture-%cc%b5-negative-septic-arthritis/