Septic arthritis of the knee: the use and effect of antibiotics prior to diagnostic aspiration

Utility of Synovial Fluid Biomarkers for Culture-Positive Septic Arthritis in a Lyme Disease-Endemic Region

OBJECTIVE

To evaluate the performance of synovial fluid biomarkers to identify children with culture-positive septic arthritis.

METHODS

We identified children 6 months to 18 years old presenting to a single emergency department between 2007 and 2022 undergoing evaluation for septic arthritis defined by having a synovial fluid culture obtained. Our primary outcome was septic arthritis defined by a positive synovial fluid culture. We evaluated the ability of synovial fluid biomarkers to identify children with septic arthritis using area under the receiver operating characteristic curve (AUC) analyses. We measured the sensitivity and specificity of commonly used synovial fluid biomarkers.

RESULTS

We included 796 children, of whom 79 (10%) had septic arthritis. Compared with synovial white blood cell count (AUC, 0.72; 95% confidence interval [CI], 0.65-0.78), absolute neutrophil count (AUC, 0.72; 95% CI, 0.66-0.79; P = 0.09), percent neutrophils (AUC, 0.66; 95% CI, 0.60-0.71; P = 0.12), and glucose (AUC, 0.78; 95% CI, 0.67-0.90; P = 0.33) performed similarly, whereas protein (AUC, 0.52; 95% CI, 0.40-0.63, P = 0.04) had lower diagnostic accuracy. Synovial fluid white blood cell count ≥50,000 cells/μL had a sensitivity of 62.0% (95% CI, 50.4%-72.7%) and a specificity of 67.0% (95% CI, 63.4%-70.4%), whereas a positive synovial fluid Gram stain had a sensitivity of 48.1% (95% CI, 36.5%-59.7%) and specificity of 99.1% (95% CI, 98.1%-99.7%) for septic arthritis.

CONCLUSIONS

None of the routinely available synovial fluid biomarkers had sufficient accuracy to be used in isolation in the identification of children with septic arthritis. New approaches including multivariate clinical prediction rules and novel biomarkers are needed.

Effect of Antibiotic Therapy Before Arthrocentesis on Synovial Fluid Cell Count and Differential for Diagnosis of Native Joint Septic Arthritis

We examined the effect of preoperative antibiotic exposure and duration on synovial fluid samples from patients with native joint septic arthritis of the hip/knee. While exposure before diagnostic arthrocentesis did not affect fluid parameters, increased duration was associated with a decreased total nucleated cell count, underscoring the complex antibiotic effects on synovial fluid parameters.

Does arthroscopic or open washout in native knee septic arthritis result in superior post-operative function? A systematic review and meta-analysis of randomised controlled trials and observational studies

AIMS

Septic arthritis (SA) of the native knee joint is associated with significant morbidity. This review compared post-operative functional outcomes (patient-reported outcome measures (PROMs) and range of movement (ROM)) following arthroscopic washout (AW) and open washout (OW) amongst adult patients with SA of the native knee. The need for further operative intervention was also considered.

METHODS

Electronic databases of PubMed, MEDLINE, Embase, Cochrane, Web of Science and Scopus were searched between 16 February 2023 and 18 March 2023. Randomised controlled trials (RCTs) and comparative observational analytic studies comparing function (reflected in PROMs or ROM) at latest follow-up following AW and OW were included. A narrative summary was provided concerning post-operative PROMs. Pooled estimates for mean ROM and re-operation rates were conducted using the random-effects model. The risk of bias was assessed using the Cochrane risk-of-bias assessment tool-2 for RCTs and the Risk of Bias in Non-Randomized Studies of Interventions tool for observational analytic studies.

RESULTS

Of 2580 retrieved citations, 7 articles (1 RCT and 6 cohort studies) met the inclusion criteria. Of these, five had some concerns/moderate risk of bias, and two had serious risk. There was a slight tendency for superior mean PROMs following AW compared with OW, but due to small effect sizes, this was unlikely clinically relevant. Additionally, the use of four different PROMs scales made direct comparisons impossible. AW was associated with superior ROM (mean difference 20.18° (95% CI 14.35, 26.02; p < 0.00001)), whilst there was a tendency for lower re-operation requirements following AW (OR 0.64, 95% CI 0.26, 1.57, p = 0.44).

CONCLUSIONS

AW was associated with equivalent to superior post-operative function and lower requirement for further intervention compared with OW. Results need to be interpreted cautiously, taking into consideration the methodological and clinical heterogeneity of the included studies.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO 2022, CRD42022364062.

Effect of Antibiotic Administration Before Joint Aspiration on Synovial Fluid White Blood Cell Count in Native Joint Septic Arthritis

Background

This study was performed to assess the impact of preaspiration antibiotics on synovial fluid analysis and timing of operative treatment in native-joint septic arthritis.

Methods

We performed a retrospective record review of adult patients from an urban level 1 trauma center with native joint septic arthritis in 2015-2019, identified by means of codes from the International Classification of Diseases (Ninth Revision and Tenth Revision). Univariate and multivariate analyses were performed to determine whether antibiotics were associated with lower synovial fluid white blood cell counts (WBCs), the percentage of polymorphonuclear neutrophil (PMNs), and rate of culture positivity. Secondary analysis included time elapsed from aspiration to surgery.

Results

Of the 126 patients with septic joints included, nearly two-thirds (n = 80 [63.5%]) received antibiotics before joint aspiration. The synovial fluid WBC count, percentage of PMNs, and rate of culture positivity were significantly lower in patients who received preaspiration antibiotics than in those who did not (mean WBC count, 51 379.1/μL [standard deviation, 52 576.3/μL] vs 92 162.7/μL [59 330.6/μL], respectively [P < .001]; PMN percentage, 83.6% [20.5%] vs 91.9% [6.0%; P = .01]; and culture positivity, 32.5% vs 59.1% [P = .008]). Multivariable analyses revealed that these associations remained after controlling for potential confounders (change in PMNs, -42 784.60/μL [95% confidence interval, -65 355/μL to -20 213.90/μL [P < .001]; change in PMNs, -7.8% [-13.7% to -1.8%] [P = .01]; odds ratio, 0.39 [.18-.87; P = .02). Patients with a synovial fluid WBC count ≤50 000/μL experienced significant delay in time from joint aspiration to operative intervention (mean [standard deviation], 10.5 [11.3] vs 17.9 [17.2] hours; P = .02).

Conclusions

The administration of antibiotics before joint aspiration for suspected septic arthritis appears to decrease the synovial fluid WBC count, the percentage of PMNs, and the rate of culture positivity. Efforts to limit antibiotic administration before joint aspiration are important to minimize diagnostic dilemmas and circumvent treatment delays.

Arthroscopic versus open irrigation and debridement in native knee septic arthritis: A retrospective review

Introduction

Native knee septic arthritis is a rare condition with a potential for high morbidity if not promptly treated. Treatment involves surgical decompression of the affected joint along with systemic antibiotic therapy. The purpose of this study is to compare arthroscopic versus open irrigation and debridement for treatment of native knee septic arthritis.

Methods

A retrospective review was conducted at a single academic institution of all patients treated for native knee septic arthritis from January 2007 until August 2018 utilizing ICD and CPT codes. Patient demographics, type of surgical procedure, need for reoperation, laboratory values, length of stay, and comorbidities were compared.

Results

A cohort of sixty-six patients who underwent 85 surgeries were included. Among these surgeries, 52 (61%) were arthroscopic while 33 (39%) were open arthrotomies, and 21% required more than one operation. While not statistically significant, the odds of reoperation was higher for those that underwent arthroscopic compared to open irrigation and debridement on univariable (OR = 4.05, p = .08) and multivariable analysis (OR = 4.39, p = .10). Additionally, patients were more likely to require a longer hospital stay if they initially underwent arthroscopic rather than open debridement (RR = 1.31, p = .02).

Conclusion

Native knee septic arthritis can be treated with a single surgery in the majority of cases. In our sample, there was an increased odds of reoperation in those treated arthroscopically compared to open, though this finding was not statistically significant. We found longer length of stay for patients undergoing arthroscopic rather than open irrigation and debridement - even after controlling for multiple operations, culture status, sex, age, and comorbidities.

Influence of Staphylococcus epidermidis on Collagen Crimp Patterns of Soft Tissue Allograft

BACKGROUND

Postoperative infections, commonly from Staphylococcus epidermidis, may result in anterior cruciate ligament graft failure and necessitate revision surgery. In biomechanical studies, S. epidermidis has been shown to establish biofilms on tendons and reduce graft strength.

PURPOSE/HYPOTHESIS

The goal of this study was to determine the effect of bacterial bioburden on the collagen structure of tendon. It was hypothesized that an increase in S. epidermidis biofilm would compromise tendon crimp, a pattern necessary for mechanical integrity, of soft tissue allografts.

STUDY DESIGN

Controlled laboratory study.

METHODS

Cultures of S. epidermidis were used to inoculate tibialis anterior cadaveric tendons. Conditions assessed included 5 × 105 colony-forming units or concentrated spent media from culture (no living bacteria). Incubation times of 30 minutes, 3 hours, 6 hours, and 24 hours were utilized. Second-harmonic generation imaging allowed for visualization of collagen autofluorescence. Crimp lengths were determined using ImageJ and compared based on incubation time.

RESULTS

Incubation time positively correlated with increasing S. epidermidis bioburden. Both fine and coarse crimp patterns lengthened with increasing incubation time. Significant coarse crimp changes were observed after only 30-minute incubations (P < .029), whereas significant fine crimp lengthening occurred after 6 hours (P < .0001). No changes in crimp length were identified after incubation in media lacking living bacteria.

CONCLUSION

The results of this study demonstrate that exposure to S. epidermidis negatively affects collagen crimp structure. Structural alterations at the collagen fiber level occur within 30 minutes of exposure to media containing S. epidermidis.

CLINICAL RELEVANCE

Our study highlights the need for antimicrobial precautions to prevent graft colonization and maximize graft mechanical strength.

Efficacy of Lavage by Tube under Local Anesthesia versus Arthroscopic Treatment of Acute Septic Arthritis of Native Knee

Although arthroscopic treatment is a minimally invasive surgery that effectively treats septic arthritis of the knee joint, it requires general or regional anesthesia. This study aimed to compare the clinical results of lavage after tube insertion versus arthroscopic treatment. Patients treated with arthroscopic treatment were included in group I (n = 76), while those treated with lavage by tube were included in group II (n = 34). We investigated the following in all patients: demographics, underlying disorders, initial serum white blood cell (WBC) count, C-reactive protein (CRP) level, synovial fluid WBC and polymorphonuclear cell counts, causative organism, initial Kellgren-Lawrence grade, lavage number, interventional delay, hospitalization days, CRP normalization time, and Western Ontario McMaster Universities Osteoarthritis index scores for clinical outcomes at 3 months postoperative. The mean interventional delay was significantly greater in group I (23.6 ± 15.6 h vs. 8.7 ± 9.3 h, p < 0.001). The lavage by tube featured a significantly shorter interventional delay time than arthroscopy, while the CRP decrease rate did not differ between groups. Moreover, lavage by tube showed no significant differences in outcomes, including laboratory results and functional outcomes at 3 months postoperative.

Retrospective evaluation of 103 cases of septic arthritis in dogs

OBJECTIVE

This study examines inciting causes, diagnosis, treatment and risk factors for the recurrence and outcome of septic arthritis (SA) in dogs.

STUDY DESIGN

Medical records spanning 17 years from five referral hospitals were surveyed for presumptive and confirmed cases of SA.

RESULTS

SA was identified in 103 cases. Spontaneous septic SA was the most common inciting cause. The most commonly affected joints were the stifle (40%) and elbow (24%). Pre-existing osteoarthritis (OA) was present in 63% of septic joints and was associated with recurrence (p = 0.03). Treatment with antibiotics prior to presentation was associated with a negative synovial fluid culture (p = 0.014). A successful outcome was associated with early treatment (p = 0.001) and SA due to direct penetration (p = 0.04) or spontaneous cause (p = 0.003). Recurrence was more likely in dogs with unsuccessful outcomes (p = 0.004) and bodyweights >30 kg (p = 0.009).

CLINICAL SIGNIFICANCE

SA should be considered as a differential diagnosis in large breed dogs with pre-existing OA presenting with either an acute or chronic monoarthropathy. In the majority of cases, a successful outcome was achieved regardless of treatment type. Recurrence rates were low, but associated with pre-existing OA and higher bodyweight. Although treatment should be implemented as soon as possible to maximise outcome success, synovial fluid samples should ideally be obtained before empiric antibiotic administration.

Synovial fluid leukocyte cell count before versus after administration of antibiotics in patients with septic arthritis of a native joint

BACKGROUND

Antibiotics have been shown to affect the accuracy of cultures; so antibiotics are held prior to obtaining cultures intra-operatively. No study has evaluated the effects of antibiotics on synovial fluid leukocyte cell count. The purpose of the current study is to compare the leukocyte cell count of native joints with septic arthritis when antibiotics have been given before aspiration and when no antibiotics have been given prior to aspiration.

METHODS

This study was performed at a community hospital and a level 1 urban trauma hospital after IRB approval from both institutions from July 2007 to July 2017. Inclusion criteria comprised of a diagnosis of septic arthritis with positive cultures and a recorded arthrocentesis with cell count performed. Patients with septic arthritis were identified using ICD-9 codes 711.00-711.99 and ICD-10 codes M00 - M02. A retrospective chart review was performed and data was collected. Patients were placed into one of two groups. Group 1 received no antibiotics for two weeks prior to arthrocentesis, group 2 received antibiotics within 24 h prior to arthrocentesis. Demographic information, cell count number and differential, and blood lab values were collected. Timing data was also collected on timing of admission, antibiotics, joint irrigation, and discharge from the inpatient setting.

RESULTS

There were 81 patients meeting final inclusion criteria. The average cell count for the group which received antibiotics (n = 30) was 40,408 ± 29,433 while the average cell count for the group receiving no antibiotics (n = 51) was 93,824 ± 73,875 (p < .0001). The average length of stay was not significantly different between the antibiotic group versus no antibiotic group (14.0 days vs 12.1 days p = .4). The time from admission to arthrocentesis and admission to washout was longer for the antibiotic group versus no antibiotic group (p = .004 and p = .002, respectively).

CONCLUSION

When antibiotics are given prior to arthrocentesis of a septic joint, there is an associated lower synovial fluid leukocyte count compared to when no antibiotics are given prior.

LEVEL OF EVIDENCE

Level III.

Septic Arthritis: An Evidence-Based Review of Diagnosis and Image-Guided Aspiration

OBJECTIVE. The purpose of this evidence-based review is to equip radiologists to discuss and interpret findings obtained with various imaging modalities, guide patient selection for percutaneous aspiration, and safely perform arthrocentesis to assess for infection in both native and prosthetic joints. CONCLUSION. Septic arthritis is an emergency that can lead to rapidly progressive, irreversible joint damage. Despite the urgency associated with this diagnosis, there remains a lack of consensus regarding many aspects of the management of native and periprosthetic joint infections.

2020 French recommendations on the management of septic arthritis in an adult native joint

Septic arthritis (SA) in an adult native joint is a rare condition but a diagnostic emergency due to the morbidity and mortality and the functional risk related to structural damage. Current management varies and the recommendations available are dated. The French Rheumatology Society (SFR) Bone and Joint Infection Working Group, together with the French Language Infectious Diseases Society (SPILF) and the French Orthopaedic and Trauma Surgery Society (SOFCOT) have worked according to the HAS methodology to devise clinical practice recommendations to diagnose and treat SA in an adult native joint. One new focus is on the importance of microbiological documentation (blood cultures and joint aspiration) before starting antibiotic treatment, looking for differential diagnoses (microcrystal detection), the relevance of a joint ultrasound to guide aspiration, and the indication to perform a reference X-ray. A cardiac ultrasound is indicated only in cases of SA involving Staphylococcus aureus, oral streptococci, Streptococcus gallolyticus or Enterococcus faecalis, or when infective endocarditis is clinically suspected. Regarding treatment, we stress the importance of medical and surgical collaboration. Antibiotic therapies (drugs and durations) are presented in the form of didactic tables according to the main bacteria in question (staphylococci, streptococci and gram-negative rods). Probabilistic antibiotic therapy should only be used for patients with serious symptoms. Lastly, non-drug treatments such as joint drainage and early physical therapy are the subject of specific recommendations.

Antimicrobial susceptibility patterns of bacterial isolates cultured from synovial fluid samples from horses with suspected septic synovitis: 108 cases (2008-2017)

OBJECTIVE

To describe the antimicrobial susceptibility patterns of the most commonly isolated bacteria cultured from synovial fluid samples from horses with suspected septic synovitis treated at an equine referral hospital between May 1, 2008, and September 24, 2017.

SAMPLE

131 synovial fluid samples from 108 client-owned horses.

PROCEDURES

A retrospective medical record search was conducted to identify horses with suspected septic synovitis and results of synovial fluid bacterial culture and antimicrobial susceptibility testing. Data collected included signalment, known or suspected origin of synovial contamination, synovial structures affected, antimicrobial treatment, and results of synovial fluid cytologic evaluation and bacterial culture and susceptibility testing. Horses were grouped as adults (≥ 6 months old) or foals (< 6 months old).

RESULTS

Results of bacterial culture were positive for 34 of 70 (49%) and 18 of 61 (30%) samples from 68 adult horses and 40 foals, respectively. Gram-positive bacteria were more common in adult horses, whereas gram-negative bacteria were more common in foals. No multidrug-resistant microorganisms were identified. For adult horses, 92% (23/25) of gram-positive isolates tested with penicillin and gentamicin were susceptible to the combination. For foals, 94% (15/16) of isolates tested with penicillin, gentamicin, or both had susceptibility to 1 or both antimicrobials.

CONCLUSIONS AND CLINICAL RELEVANCE

Periodic review of bacterial profiles and antimicrobial susceptibility in horses with septic synovitis can help to detect early changes in bacterial pressure and antimicrobial resistance. Findings suggested that in the geographic area we serve, a combination of penicillin and gentamicin would be an effective empirical antimicrobial treatment for most horses with septic synovitis while results of bacterial culture and susceptibility are pending.

Acute Gout Attack Immediately After Total Knee Arthroplasty: A Case Report

CASE

We report a case of acute gouty arthritis-mimicking infection that occurred immediately after right total knee arthroplasty in a 73-year-old man. Repetitive laboratory tests showed acute inflammation and did not easily distinguish acute gout from bacterial infection. Surgical treatment was undertaken for diagnostic and therapeutic purposes. A large amount of chalky whitish crystals suggestive of acute gout was found in both knees without the suspicion of bacterial infection, and thorough irrigation and debridement were performed.

CONCLUSIONS

Although conservative treatment is generally administered for acute gouty arthritis, early surgical intervention may ensure a good clinical result in a prosthetic joint.

Pilot study of a novel serum mRNA gene panel for diagnosis of acute septic arthritis

BACKGROUND

Septic arthritis is an orthopedic emergency requiring immediate surgical intervention. Current diagnostic standard of care is an invasive joint aspiration. Aspirations provide information about the inflammatory cells in the sample within a few hours, but there is often ambiguity about whether the source is infectious (e.g. bacterial) or non-infectious (e.g. gout). Cultures can take days to result, so decisions about surgery are often made with incomplete data. Novel diagnostics are thus needed. The “Sepsis MetaScore” (SMS) is an 11-mRNA host immune blood signature that can distinguish between infectious and non-infectious acute inflammation. It has been validated in multiple cohorts across heterogeneous clinical settings.

AIM

To study whether the SMS holds diagnostic validity in determining the etiology of acute arthritis.

METHODS

We conducted a blinded, prospective, non-interventional clinical study of the SMS. All patients undergoing work-up for a septic primary joint were enrolled. Patients proceeded through the normal standard-of-care pathway, including joint aspiration and inflammatory labs [white blood cell (WBC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP)]. Venous blood was also drawn into PAX gene RNA-stabilizing tubes and mRNAs were measured using Nano String nCounter™. SMS was calculated blinded to clinical results.

RESULTS

A total of 20 samples were included, of which 11 were infected based on aspiration or intra-operative cultures. The SMS had an area under the ROC curve (AUROC) of 0.87 for separating infectious from non-infectious conditions. For comparison, the AUROCs for ESR = 0.58, CRP = 0.6, and WBC = 0.59. At 100% sensitivity for infection, the specificity of the SMS was 40%, meaning nearly half of non-septic patients could have been ruled out for further intervention.

CONCLUSION

In this pilot study, SMS showed a high level of diagnostic accuracy in predicting septic joints compared to other diagnostic biomarkers. This quick blood test could be an important tool for early, accurate identification of acute septic joints and need for emergent surgery, improving clinical care and healthcare spending.

Diagnosis of peripheral bone and prosthetic joint infections: overview on the consensus documents by the EANM, EBJIS, and ESR (with ESCMID endorsement)

OBJECTIVES

Peripheral bone infection (PBI) and prosthetic joint infection (PJI) are two different infectious conditions of the musculoskeletal system. They have in common to be quite challenging to be diagnosed and no clear diagnostic flowchart has been established. Thus, a conjoined initiative on these two topics has been initiated by the European Society of Radiology (ESR), the European Association of Nuclear Medicine (EANM), the European Bone and Joint Infection Society (EBJIS), and the European Society of Clinical Microbiology and Infectious Diseases (ESCMID). The purpose of this work is to provide an overview on the two consensus documents on PBI and PJI that originated by the conjoined work of the ESR, EANM, and EBJIS (with ESCMID endorsement).

METHODS AND RESULTS

After literature search, a list of 18 statements for PBI and 25 statements for PJI were drafted in consensus on the most debated diagnostic challenges on these two topics, with emphasis on imaging.

CONCLUSIONS

Overall, white blood cell scintigraphy and magnetic resonance imaging have individually demonstrated the highest diagnostic performance over other imaging modalities for the diagnosis of PBI and PJI. However, the choice of which advanced diagnostic modality to use first depends on several factors, such as the benefit for the patient, local experience of imaging specialists, costs, and availability. Since robust, comparative studies among most tests do not exist, the proposed flowcharts are based not only on existing literature but also on the opinion of multiple experts involved on these topics.

KEY POINTS

• For peripheral bone infection and prosthetic joint infection, white blood cell and magnetic resonance imaging have individually demonstrated the highest diagnostic performance over other imaging modalities. • Two evidence- and expert-based diagnostic flowcharts involving variable combination of laboratory tests, biopsy methods, and radiological and nuclear medicine imaging modalities are proposed by a multi-society expert panel. • Clinical application of these flowcharts depends on several factors, such as the benefit for the patient, local experience, costs, and availability.

Consensus document for the diagnosis of prosthetic joint infections: a joint paper by the EANM, EBJIS, and ESR (with ESCMID endorsement)

Background

For the diagnosis of prosthetic joint infection, real evidence-based guidelines to aid clinicians in choosing the most accurate diagnostic strategy are lacking.

Aim and Methods

To address this need, we performed a multidisciplinary systematic review of relevant nuclear medicine, radiological, orthopaedic, infectious, and microbiological literature to define the diagnostic accuracy of each diagnostic technique and to address and provide evidence-based answers on uniform statements for each topic that was found to be important to develop a commonly agreed upon diagnostic flowchart.

Results and Conclusion

The approach used to prepare this set of multidisciplinary guidelines was to define statements of interest and follow the procedure indicated by the Oxford Centre for Evidence-based Medicine (OCEBM).

Electronic supplementary material

The online version of this article (10.1007/s00259-019-4263-9) contains supplementary material, which is available to authorized users.

The impact of lifestyle risk factors on the rate of infection after surgery for a fracture of the ankle

Aims

Lifestyle risk factors are thought to increase the risk of infection after acute orthopaedic surgery but the evidence is scarce. We aimed to investigate whether smoking, obesity and alcohol overuse are risk factors for the development of infections after surgery for a fracture of the ankle.

Patients and Methods

We retrospectively reviewed all patients who underwent internal fixation of a fracture of the ankle between 2008 and 2013. The primary outcome was the rate of deep infection and the secondary outcome was any surgical site infection (SSI). Associations with the risk factors and possible confounding variables were analysed univariably and multivariably with backwards elimination.

Results

A total of 1043 patients were included; 64 (6.1%) had a deep infection and 146 (14.0%) had SSI. Obesity was strongly associated with both outcomes (odds ratio (OR) 2.21, p = 0.017 and OR 1.68, p = 0.032) in all analyses. Alcohol overuse was similarly associated, though significant only in unadjusted analyses. Surprisingly, smoking did not yield statistically significant associations with infections.

Conclusion

These findings suggest that obesity and possibly alcohol overuse are independent risk factors for the development of infection following surgery for a fracture of the ankle. This large study brings new evidence concerning these common risk factors; although prospective studies are needed to confirm causality. Cite this article: Bone Joint J 2017;99-B:225–30.

Adult Native Septic Arthritis in an Inner City Hospital: Effects on Length of Stay

The objective of this retrospective study was to assess what factors affected length of stay (LOS) in 183 adult patients with native septic arthritis. Diagnosis was based on a representative physical examination, fluid cell count/Gram stain, and organisms isolated from joint fluid culture. Data included demographics, comorbidities, laboratory results, treatment, and discharge times. Joint fluid cultures were positive in 55% (100 of 183) of the patients, and these patients were the subjects of this study. Blood cultures were taken for 65 patients and were positive in 54%; when positive, they were found to be the same as isolates from joint fluid analysis 91% of the time. Pathogens found in joint fluid analysis were as follows: methicillin-susceptible Staphylococcus aureus (MSSA), 44%; methicillin-resistant S aureus (MRSA), 21%; Streptococcus species, 14%; Pseudomonas, 10%; and other organisms, 11%. Surgical washout less than 24 hours from diagnosis affected LOS (12.25 vs 16.96 days for >24 hours; P<.05), but pathogen type and comorbid conditions did not. Average time for culture sensitivities was 4±1 days. Almost half of the patients had MSSA. Delays that could be controlled were getting an early diagnosis and expedient surgical washout of the joint. A lack of insurance and a requirement of intravenous antibiotics prolonged stay, whereas age, sex, and ethnicity did not. Waiting for bacterial sensitivities was a factor that could not be controlled. The authors believe that polymerase chain reaction or other technologies could lead to early diagnosis and expedient surgery. Effective oral antibiotics against resistant organisms would help the patients leave the hospital earlier. [Orthopedics. 2016; 39(4):e674-e679.].

Etiology of bone and joint infections: a case series of 363 consecutive patients from an orthopaedic infection unit

BACKGROUND

Bone and joint infections remain a clinical challenge with potentially serious consequences. Nevertheless there is a lack of studies with strict criteria for diagnosis and etiology. The primary aim of this study was to determine the causative agents in orthopaedic infections using strict diagnostic criteria for infection and etiology. The secondary aim was to assess the timing of post-operative infections in relation to pathogens and to compare causative bacteria in different parts of the body.

METHODS

A retrospective registry study of 363 consecutive cases of bone and joint infections was performed. Microbiological data on sampling and culture results were registered.

RESULTS

Staphylococcus aureus dominated in both operated (45%) and non-operated (44%) patients, followed in frequency by coagulase-negative staphylococci (CoNS) in operated patients (11%) and beta-haemolytic streptococci in non-operated patients (16%) (p < 0.001). There were no polymicrobial infections in non-surgical cases (p < 0.001). For operated patients, Gram-negative bacilli were observed in 6%, almost exclusively isolated from the lower extremity. Propionibacterium spp. was the most common finding after spinal surgery. In 90/363 (25%), the agent responsible for the infection could not be defined according to the strict criteria used.

CONCLUSION

S. aureus dominated as etiological agent in all bone and joint infections, including operated patient given peri-operative prophylaxis. Improved timing of antibiotic prophylaxis seen after the introduction of the Swedish national project PRISS may have changed this. The number of infections with uncertain etiology was high, stressing the importance of more studies on diagnostics, as well as strict diagnostic algorithms.

Evaluation of a Genus- and Group-Specific Rapid PCR Assay Panel on Synovial Fluid for Diagnosis of Prosthetic Knee Infection

We evaluated a genus- and group-specific PCR assay panel using 284 prosthetic knee synovial fluid samples collected from patients presenting to our institution with implant failure. Using the Musculoskeletal Infection Society diagnostic criteria, 88 and 196 samples were classified as showing prosthetic joint infection (PJI) and aseptic failure (AF), respectively. Sensitivities of the synovial fluid PCR panel and culture were 55.6% and 76.1% (P ≤ 0.001), respectively, and specificities were 91.8% and 97.4% (P = 0.016), respectively. Among the 70 subjects who had received antibiotics within the month preceding synovial fluid aspiration (48 of whom had PJI), PCR panel and synovial fluid culture sensitivities were 64.5% and 85.4%, respectively (P < 0.0001). In this group, the PCR panel detected Staphylococcus aureus in two culture-negative PJI cases. Overall, the evaluated molecular diagnostic tool had low sensitivity when applied to synovial fluid.

Conventional diagnostic challenges in periprosthetic joint infection

Periprosthetic joint infection remains a clinical challenge with no benchmark for diagnosis. The diagnosis is based on many different clinical variables that may be difficult to interpret, especially in the setting of chronic systemic disease. Synovial fluid aspiration, diagnostic imaging, traditional culture, peripheral serum inflammatory markers, and intraoperative frozen sections each have their limitations but continue to be the mainstay for diagnosis of periprosthetic joint infection. As molecular- and biomarker-based technologies improve, the way we interpret and diagnose periprosthetic joint infection will ultimately change and may even improve diagnostic accuracy and turnaround time. Future research on this topic should be focused on improving diagnostic criteria for low-virulence organisms, improving interpretation of intraoperative frozen sections, and establishing improved synovial fluid and peripheral serum biomarker profiles for periprosthetic joint infection.

Synovial fluid findings in children with knee monoarthritis in lyme disease endemic areas

BACKGROUND

Although Lyme and septic arthritis of the knee may have similar clinical presentations, septic arthritis requires prompt identification and treatment to avoid joint destruction. We sought to determine whether synovial fluid cell counts alone can discriminate between Lyme, septic, and other inflammatory arthritis.

METHODS

We conducted a retrospective cohort study of children aged 1 to 18 years with knee monoarthritis who presented to 1 of 2 pediatric emergency departments located in Lyme endemic areas. We included children who had both a synovial fluid culture and an evaluation for Lyme disease. Septic arthritis was defined as a positive synovial fluid culture or synovial fluid pleocytosis (white blood cell [WBC] ≥40,000 cells/μL) with a positive blood culture. Lyme arthritis was defined as positive Lyme serology without a positive bacterial culture. All other children were considered to have other inflammatory arthritis. We compared the synovial fluid counts by arthritis type.

RESULTS

We identified 384 children with knee monoarthritis, of whom 19 (5%) had septic arthritis, 257 (67%) had Lyme arthritis and 108 (28%) had other inflammatory arthritis. Children with other inflammatory arthritis had lower synovial WBC and absolute neutrophil count, as well as percent neutrophils, than those with either Lyme or septic arthritis. There were no significant differences in the synovial fluid WBC, absolute neutrophil count, and percent neutrophils for children with Lyme and septic arthritis.

CONCLUSIONS

In Lyme endemic areas, synovial fluid results alone do not differentiate septic from Lyme arthritis. Therefore, other clinical or laboratory indicators are needed to direct the care of patients with knee monoarthritis.

Multifocal infections of the musculoskeletal system: description of a safe one-step procedure for eradication of associated spinal infections

BACKGROUND

The aim of this study was to evaluate the clinical outcome after radical surgical treatment of multifocal infections involving the spine.

METHODS

The study demonstrates a retrospective chart review of seven patients who had more than three different abscesses in the musculoskeletal system and at least one of them in the area of the spinal column. All patients had a sepsis.

RESULTS

Beside different musculoskeletal abscesses four patients had a spondylodiscitis in the cervical spine segments C4/5 or C5/6. Six patients had inflammatory processes in the lumbar spine with epidural abscesses, diffuse thoracolumbar paravertebral abscesses and a spondylodiscitis in different segments. In all cases we performed a radical surgical treatment of all related inflammatory focuses. Prompt radical surgical treatment of the spine included decompression, debridement and in the cases of spondylodiscitis a fusion of the involved segments. For more than one focus at the spine, a surgical one-step procedure was performed. An antibiotic therapy was administered for six to eight weeks. In follow up examinations no signs of ongoing inflammatory processes were seen in imaging studies or laboratory tests.

CONCLUSIONS

In the event of multiple abscesses of the musculoskeletal system involving the spine an early correct diagnosis and radical surgical treatment is recommended. We strongly favor a surgical single-stage procedure for treatment of multiple infections of the spine. In addition to a radical debridement and a sufficient decompression, the segmental fusion of affected areas in spondylodiscitis is essential. At the same time a surgical therapy of all other infected sites should be performed.