What Is the Best Technique for Performing Aspiration of Patients With Total Ankle Arthroplasty (TAA)?

Recommendation: In the absence of evidence, we recommend that ankle joint aspiration to evaluate for periprosthetic joint infection (PJI) be performed under sterile conditions via the anteromedial approach. Ultrasound guidance may be used if available but is not necessary to obtain an acceptable synovial fluid sample. Level of Evidence: Consensus. Delegate Vote: Agree: 100%, Disagree: 0%, Abstain: 0% (Unanimous, Strongest Consensus)

THE EPIDEMIOLOGY AND CLINICAL FEATURES OF SEPTIC ARTHRITIS CASES SECONDARY TO KINGELLA KINGAE IN COMPARISON TO SEPTIC ARTHRITIS FROM OTHER PATHOGENS

BACKGROUND In Europe, Kingella kingae (Kk) is considered as a significant pathogen in osteoarticular infections (OAI) in young children. Some authors suggest that a significant portion of ‘culture negative septic arthritis’ may be secondary to the inability to isolate K. kingae using conventional methods. However, its pathogenic role and prevalence remain controversial in North America. Since 2014, in order to optimize the microbiological diagnosis of OAI, all osteo-articular specimens submitted to our laboratory for bacteriology culture were simultaneously tested with a home brew multiplex PCR assay detecting Kk, Staphylococcus aureus, Streptococcus pyogenes, Streptococcus agalactiae and Streptococcus pneumoniae. Consequently, an important increase in Kk OAI proven cases was observed. The clinical presentation of Kk OAI comparatively to the other most common pathogens seen in paediatric OAI has yet to be described in North America. OBJECTIVES The aim of this study is to review all cases of acute septic arthritis (SA) in our institution to define the prevalence of Kk SA and to compare the clinical presentation of SA cases according to their bacterial etiology, with a deeper look at SA caused by Kk. DESIGN/METHODS We conducted a retrospective chart review of all cases of suspected SA who had a synovial fluid sample submitted for bacteriology culture and multiplex PCR analysis to our microbiology laboratory between May 2014 and May 2017. Only cases of acute SA (< 1 month symptom duration prior to diagnosis) were included. Children with final diagnosis that were not of infectious origin (e.g. rheumatoid arthritis, transient synovitis, etc) were excluded. Probable SA cases were defined as cases with a clinical presentation concordant with SA without any causative bacteria identified, that have received antibiotic treatment for >2 weeks. Eligible SA cases were then stratified into 4 groups according to the final microbiology diagnosis: Kk SA, S. aureus SA, “other bacteria” SA or probable SA. One-way ANOVA with Tukey’s multiple comparison test if appropriate was subsequently performed to compare demographics, clinical and biochemical data, duration of treatment and outcome between subgroups. RESULTS Of the 153 patients who submitted a synovial fluid sample, 71 met the inclusion criteria. A microorganism was found in 56 patients (79%): Kk was found in 37 cases (52%), S. aureus in 11 cases (15%), S. pyogenes in 7 patients (10%), and Salmonella in 1 patient (1%); and there were15 probable SA cases (21%). Interestingly, Kk cases were proven by PCR only in 86% (n=32/37) of cases (culture was negative). One-way ANOVA showed a significant difference in age between subgroups [F(3, 67) = 13,60, p<0,0001]:patients infected by Kk were younger (M=1,50 years old, SD=0,68) than S. aureus (M=7.48, SD=4.84), “other bacteria” (M=5,86, SD=4,37) and probable SA subgroups (M=5,80, SD=4,90). The duration of fever (days) was shorter [F(3, 67) = 14,07, p=0,028] in patients with Kk (M=4,1, SD=3,3) and probable SA (M=2,9 SD=3,6) in comparison to “other bacteria” cases (M=8,8, SD=8,3). Also, maximal CRP values [F(3, 67) = 14,80, p<0,0001] were lower in Kk (M=42,7, SD=38,1) and probable SA (M=36,4, SD=34,6) than in SA caused by other bacteria (M=178,5, SD=98,8). Similarly, maximal neutrophil count [F(3, 67) = 6.71, p=0,0005] was lower in Kk cases (M=5,6 SD=2,3) in comparison to those infected by other bacteria (M=11,6, SD=4,1). CONCLUSION In our institution, since the implementation of multiplex PCR testing for OA samples, Kk has become the most prevalent pathogen causing SA. Children with Kk SA appear to be younger and to have a less inflammatory clinical presentation, as shown by a shorter duration of fever, lower CRP and lower neutrophil values in comparison to cases attributable to other bacteria. Prevalence of Kk SA is probably underestimated in settings where only bacteriology culture is performed.

The effect of blood contamination on equine synovial fluid analysis

Summary Objective: Based on a systemic complete blood count and a synovial fluid sample, to develop a mathematical model enabling the approximation of corrected values for synovial fluid white blood cell (WBC) count, neutrophil percentage, and total protein concentration in samples of synovial fluid that were contaminated by blood. Methods: Peripheral venous blood and synovial fluid samples were obtained from ten horses. A pooled synovial fluid sample from each horse was separated into 2 mL aliquots, which were subsequently contaminated with a known percentage of autogenous blood (0 to 50% of the synovial fluid volume). A complete blood count, packed cell volume, total protein (TP) concentration, and differential cytological examination were performed in all the synovial fluid and venous blood samples. Regression analysis was used to generate a model to calculate non-contaminated synovial WBC count, TP concentration and synovial neutrophil percentage. Using a further five horses these models were applied in blinded fashion to contaminated synovial fluid samples. Calculated values were compared to non-contaminated measured values. Results: Model results for synovial WBC count and TP concentration were not significantly different from measured values. Calculated neutrophil percentage of synovial fluid WBC was a mean of 6.6% higher than measured values and was significantly different. There was no effect of the severity of contamination (as a percentage of volume) on the ability of the models to predict any of the outcome variables. Clinical significance: It is possible to calculate non-contaminated synovial fluid WBC and TP values, but not neutrophil percentage, from heavily contaminated samples. Further study would allow for improved prediction, validation and extrapolation to a wider horse population.