Management of pediatric patients with synovial fluid white blood-cell counts of 25,000 to 75,000 cells/mm³ after aspiration of the hip

Aspirations Dashed: Conventional Synovial Fluid Analysis Is Superior to Synovial Fluid and Blood Neutrophil-to-Lymphocyte Ratios in Diagnosing Pediatric Septic Arthritis of the Hip and Knee

INTRODUCTION

Recent research suggests that synovial fluid neutrophil-to-lymphocyte ratio (SF-NLR) is a superior diagnostic for pyogenic septic arthritis (SA) in adults compared with synovial fluid white blood cell count (SF-WBC) ≥50,000 cells/μL or ≥90% polymorphonuclear leukocytes (SF-%PMN). Other research also indicates that the neutrophil-to-lymphocyte ratio in the blood (B-NLR) may be of diagnostic significance. However, it is not known whether these findings extend to the pediatric population.

METHODS

Medical records at a large urban tertiary-care children's hospital were queried for emergency department visits between 2012 and 2023, where synovial fluid (SF) analysis was performed to evaluate for SA of the hip or knee. Patients 18 years old and above were excluded. The "conventional composite test" (CCT) for SA was considered positive if SF analysis showed any of the following: (1) SF-WBC ≥50,000 cells/μL, (2) ≥90% PMNs, or (3) organisms reported on gram stain. Patients with aspirate and/or operating room (OR) cultures (or supplemental testing, ie, nucleic acid identification) revealing an offending organism were considered to have culture-positive septic arthritis (CPSA). The remaining patients were considered culture-negative (CN). Serum and SF test data were analyzed to assess their diagnostic utility in identifying CPSA. Receiver operating characteristic (ROC) curves were examined to compare the predictive value of SF-NLR and B-NLR versus conventional indicators of SA.

RESULTS

A total of 394 patients met the inclusion criteria. In all, 58.6% (n=231) were male, 67.5% (n=266) involved the knee, and 20.1% (n=79) had CPSA. Those with CPSA had higher ESR and CRP compared with CN patients (P<0.01). Bivariate testing did not show a difference in SF-NLR or B-NLR between those with CPSA and CN patients (P=0.93 and 0.37, respectively). The CCT showed 91% sensitivity and 35% specificity using conventional thresholds. ROC analysis showed that SF-WBC was superior to SF-NLR and B-NLR in the diagnosis of CPSA (AUC=0.71 vs. 0.50 and 0.53, respectively; both P<0.01). Among CCT (+) patients who ended up culture negative, Lyme testing was positive in 48.8% (100/205).

CONCLUSION

In contrast to adults, SF-NLR and B-NLR were not found to be strong diagnostic indicators of SA of the hip or knee in pediatric patients. This may be because competing diagnoses in children come with systemic inflammatory responses similar to that seen in pyogenic SA, while noninfectious conditions that might represent the major alternate diagnoses in adults do not increase systemic inflammatory markers as significantly. Given the high incidence of Lyme disease seen among patients in this study, this topic should be further studied at pediatric centers outside Lyme-endemic areas to better understand the generalizability of these findings.

SIGNIFICANCE

Despite excitement regarding SF-NLR and B-NLR as diagnostics for adult SA, these criteria appear less useful in the diagnosis of pyogenic SA in pediatric patients in Lyme-endemic areas.

Joint Fluid Cell Count in Acute Bacterial Arthritis Patients Proven Positive Culture in Children

BACKGROUND

Acute bacterial arthritis (ABA) is a serious, pediatric infection that can result in motor comorbidities. Normally, a joint fluid white blood cell (WBC) count of 50,000 or more cells/mm 3 is used to make a presumptive diagnosis of ABA. This study evaluated the utility of the joint fluid WBC count for diagnosing pediatric ABA confirmed by a positive culture result.

METHODS

Patients with ABA between March 2010 and March 2023 at Tokyo Metropolitan Children's Medical Center were included. ABA was confirmed by positive joint fluid culture results for a pathogenic organism. Patients with negative results and those without a joint fluid WBC count were excluded. Electronic medical records were retrospectively reviewed for demographic data, timing of arthrocentesis, culture results and the joint fluid WBC count.

RESULTS

Ninety-five patients with ABA were identified; of these, 22 were included. The median age was 5 years [interquartile range (IQR): 2-10 years]. Males comprised 55% of the population. The median joint fluid WBC count was 19,575 (IQR: 6806-47,388) cells/mm 3 , and 23% of the patients had 50,000 cells/mm 3 or more. The median time from symptom onset to arthrocentesis was 3 days (IQR: 2-5 days). The isolated organisms were methicillin-susceptible Staphylococcus aureus (50%), methicillin-resistant S. aureus (9%), Streptococcus pyogenes (27%), Streptococcus pneumoniae (5%), Klebsiella pneumoniae (5%) and Salmonella spp. (5%).

CONCLUSIONS

Most of the patients with ABA confirmed by positive results of a joint fluid culture had a joint fluid WBC count of less than 50,000 cells/mm 3 .

Clinical Practice Guideline by the Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA): 2023 Guideline on Diagnosis and Management of Acute Bacterial Arthritis in Pediatrics

This clinical practice guideline for the diagnosis and treatment of acute bacterial arthritis (ABA) in children was developed by a multidisciplinary panel representing the Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA). This guideline is intended for use by healthcare professionals who care for children with ABA, including specialists in pediatric infectious diseases and orthopedics. The panel's recommendations for the diagnosis and treatment of ABA are based upon evidence derived from topic-specific systematic literature reviews. Summarized below are the recommendations for the diagnosis and treatment of ABA in children. The panel followed a systematic process used in the development of other IDSA and PIDS clinical practice guidelines, which included a standardized methodology for rating the certainty of the evidence and strength of recommendation using the GRADE approach (Grading of Recommendations Assessment, Development and Evaluation) (see Figure 1). A detailed description of background, methods, evidence summary and rationale that support each recommendation, and knowledge gaps can be found online in the full text.

A devastating complication from neonate knee septic arthritis due to conservative treatment: A case report

INTRODUCTION

Septic arthritis in the neonate is a devastating condition that affects children and causes irreversible limb dysfunction or deformity. Neonatal septic arthritis is harmful and will end with skeletal abnormalities.

PRESENTATION OF CASE

Neonate born with ileal atresia and underwent surgical treatment. Postoperatively, the patient experienced sepsis and was accompanied by septic arthritis. The patient was given triple IV antibiotic treatment without surgical debridement. Ten months later the deformity became prominent with physeal destruction of the affected area at distal femur. At age six the patient came to the orthopaedic outpatient clinic and there was a 3 cm limb-length discrepancy of both legs.

DISCUSSION

Early diagnosis of septic arthritis is critical for successful treatment, since neonates with delayed proper diagnosis have been shown to have poor long-term prognosis. In our case the patient was only managed by IV antibiotics administration and continued with oral antibiotics. The reason for this decision due to general condition was improved after medication although clinically he still has a small amount of knee swelling.

CONCLUSION

Neonatal septic arthritis is dangerous and may have a devastating long term complication. Surgical management should be considered as treatment of choice if there is a lack or no progression from clinical and laboratory examination after antibiotic adiminstration. Growth arrest on the distal femur will result in leg length disparity and angular deformity.

Surgical (over) treatment of pediatric Lyme arthritis: a need for faster Borrelia testing

Pediatric Lyme arthritis is described but not well-characterized in urban populations. Similarities in clinical features between Lyme and septic arthritis also results in some patients with Lyme arthritis undergoing surgical treatment. The aims of this study are to (1) characterize Lyme arthritis in an urban population and (2) determine what factors predispose patients with Lyme arthritis to undergoing surgery. We performed a retrospective review of children with Lyme arthritis at a single academic institution in New York City from 2016 to 2021. Inclusion criteria were age ≤18 years, involvement of a major joint, and positive Lyme serology. Patients treated with irrigation and debridement were compared to those treated non-surgically using Chi-squared tests with a significance of P  < 0.05. A total of 106 children with Lyme arthritis were included. Mean age was 9.5 years; 61.3% were male, and 71.7% were Caucasian. 46.2% lived in regions with an average household income >$100 000; 70.8% had private insurance. Ten patients (9.4%) underwent surgery for suspected septic arthritis. The operative group was more likely to have an elevated heart rate, white blood cell count, C-reactive protein level, erythrocyte sedimentation rate level and synovial cell count ( P  < 0.05). Patients were more likely to undergo surgery if they presented to the emergency department than to the clinic ( P  = 0.03). The average time for a Lyme test to result was 43.5 h, averaging 8.7 h after the surgical start time. Lyme arthritis occurs commonly in an urban pediatric population. Surgery is performed in ~10% of Lyme arthritis patients. More efficient diagnostic tests may reduce this rate.

Familial Mediterranean fever with pseudo-septic arthritis: A case report and review of the literature

Familial Mediterranean fever (FMF) is a hereditary auto-inflammatory disease resulting from mutations of the MEFV gene. The disease is characterised by recurrent attacks of abdominal pain and fever. Most FMF patients develop arthritis at some point in their life usually manifesting as self-limiting monoarthritis. On very rare occasions, arthritis in FMF can mimic septic arthritis (pseudo-septic arthritis) with very similar clinical and laboratory findings. We report a case of a young male patient who presented with recurrent attacks of prolonged monoarthritis. For 2 years, he had undergone multiple admissions and operations for drainage of suspected septic joints. The synovial aspiration showed culture-negative pus with very high synovial white blood cell counts highly suggestive of septic arthritis. The patient was later found to have FMF based on homozygous M694V mutation of the MEFV gene. He was treated with colchicine monotherapy with a quick improvement of arthritis and later good control of his disease. The literature review showed very few case reports with similar presentations, most of which responded well to colchicine. FMF can mimic septic arthritis resulting in unnecessary expensive and invasive interventions and prolonged courses of antibiotics. Pseudo-septic arthritis is usually associated with M694V homozygous mutation and can complicate FMF at any time throughout the disease course. It is important to consider FMF in the differential diagnosis of septic arthritis, particularly with a family history of FMF and in patients from communities with a high prevalence of MEFV gene mutation.

Fever and Knee Effusion in the Pediatric Patient

ABSTRACT

The pediatric patient with fever and knee effusion is always a cause for clinical concern. A thorough history and physical examination is required to guide appropriate diagnostic evaluation and management. Although pediatric knee effusions are common in the setting of trauma, the presence of fever should prompt consideration of infectious, rheumatologic, vasculitic, and malignant etiologies. This review covers the key components of the history, physical examination, diagnostic strategies, common etiologies, and initial management of the pediatric patient with fever and knee effusion.

Diagnostic Utility of Synovial Fluid Cell Counts and CRP in Pediatric Knee Arthritis: A 10-Year Monocentric, Retrospective Study

Background: Orthopedic surgeons often use the intra-articular white blood counts (WBCs) and the percentage of polymorphonuclear cells (PMN) in the diagnosis of an acute swollen and painful knee joint in children. Today, there is no established threshold for the synovial WBC, and their differentiation, as indicative of native joint knee bacterial arthritis. We determine the sensitivity and specificity of synovial WBCs and PMN percentages in the prediction of a community-acquired, acute bacterial native joint septic arthritis (SA) in the pediatric population. Methods: A retrospective study on healthy children 0–16 years of age who underwent knee joint aspiration for a community-acquired, acute irritable knee effusion in our tertiary-care children’s hospital between May 2009 and April 2019 was conducted. We divided the study population into two groups according to the detection of bacterial arthritis in the synovial fluid (bacterial arthritis versus its absence) and compared the intra-articular leukocyte and C-reactive protein (CRP) levels. Results: Overall, we found a statistically significant difference regarding the total CRP (p = 0.017), leukocyte or PMN counts (p ≤ 0.001 in favor of a bacterial arthritis). In contrast, the percentage of the neutrophils was not determinant for the later confirmation of bacterial pathogens, and we were unable to establish diagnostically determining minimal thresholds of the intra-articular CRP and leukocyte levels. Conclusions: This pilot study suggests that either the leukocyte or PMN counts may be associated with a bacterial origin of knee arthritis in children. We plan a larger prospective interventional study in the future to confirm these findings including the investigation of other joint aspirate biomarkers.

Primary Septic Arthritis in Children Demonstrates Presumed and Confirmed Varieties Which Require Age-specific Evaluation and Treatment Strategies

BACKGROUND

There is uncertainty involved in the evaluation and treatment of children suspected to have septic arthritis particularly when no causative pathogen is confirmed. This study evaluates children with primary septic arthritis to refine the processes of evaluation and treatment and improve the rate of pathogen confirmation.

METHODS

Children suspected to have septic arthritis from 2009 to 2019 were retrospectively studied. Diagnosis of primary septic arthritis, defined as hematogenous joint infection without associated osteomyelitis, was established by clinical evaluation, radiology and laboratory results, including joint fluid analysis. Excluded cases were categorized by etiology. Children with primary septic arthritis were divided into confirmed and presumed cohorts for statistical comparison.

RESULTS

A total of 355 children (average age 4.4 y, range 0.05 to 18 y) were initially treated as septic arthritis. Eighty-seven (24.5%) were excluded due to other conditions, including 34 (9.6%) with noninfectious conditions. Among 268 children with primary septic arthritis, 134 were confirmed and 134 were presumed. A higher rate of 16S polymerase chain reaction (PCR) acquisition (71.6% vs. 45.5%) occurred in the confirmed cohort. Overall yield for various methods of pathogen identification were 27 of 239 (11.3%) by blood culture, 83 of 268 (31.0%) by joint fluid culture and 85 of 157 (54.1%) by PCR. PCR identified a pathogen in 87.5% of children with confirmed septic arthritis. Antibiotic pretreatment was associated with a lower rate of joint fluid culture positivity. Pathogens aggregated within specific age groups. The 4 to 9-year-old age group displayed the widest spectrum of pathogens with limited predictability.

CONCLUSIONS

This study emphasizes the need for systematic processes of evaluation and treatment for children suspected to have primary septic arthritis, including minimization of antibiotic pretreatment, age-based empiric antibiotic selection, and sufficient follow-up to ensure noninfectious conditions are distinguished in culture-negative cases. Extended observation, before intervention, may be appropriate for some children.

LEVEL OF EVIDENCE

Level III-retrospective control study.

Diagnostic Criteria for the Painful Swollen Pediatric Knee: Distinguishing Septic Arthritis From Aseptic Effusion in a Non-Lyme Endemic Area

Purpose: The child with a painful swollen knee must be worked-up for possible septic arthritis; the classic clinical prediction algorithms for septic arthritis of the hip may not be the best models to apply to the knee. Materials and methods: This was a retrospective case-control study of 17 years of children presenting to one hospital with a chief complaint of a painful swollen knee, to evaluate the appropriateness of applying a previously described clinical practice algorithm for the hip in differentiating between the septic and aseptic causes of the painful knee effusions. The diagnoses of true septic arthritis, presumed septic arthritis, and aseptic effusion were established, based upon the cultures of synovial fluid, blood cultures, synovial cell counts, and clinical course. Using a logistic regression model, the disease status was regressed on both the demographic and clinical variables. Results: In the study, 122 patients were included: 51 with true septic arthritis, 37 with presumed septic arthritis, and 34 with aseptic knee effusion. After applying a backward elimination, age <5 years and C-reactive protein (CRP) >2.0 mg/dl remained in the model, and predicted probabilities of having septic knee arthritis ranged from 15% for the lowest risk to 95% for the highest risk. Adding a knee aspiration including percent polymorphonucleocytes (%PMN) substantially improved the overall model performance, lowering the lowest risk to 11% while raising the highest risk to 96%. Conclusions: This predictive model suggests that the likelihood of pediatric septic arthritis of the knee is >90% when both "age <5 years" and "CRP > 2.0 mg/dl" are present in a child with a painful swollen knee, though, in the absence of these factors, the risk of septic arthritis remains over 15%. Aspiration of the knee for those patients would be the best next step.

Septic Arthritis of the Knee in Children: A Critical Analysis Review

» Septic arthritis of the knee is the most common type of septic arthritis in children, and it may result in irreversible joint damage. » Staphylococcus aureus is the most common pathogen associated with septic arthritis, but other causative pathogens are possible in children with certain risk factors. » The diagnosis of septic arthritis of the knee is based on history and physical examination, blood tests, and arthrocentesis. » Empiric treatment with anti-staphylococcal penicillin or a first-generation cephalosporin is usually recommended but may be tailored according to local resistance patterns and clinical culture data. » Open or arthroscopic surgical debridement including extensive lavage is effective in eradicating infection, and most patients do not require additional surgical intervention.

Test characteristics of history, examination and investigations in the evaluation for septic arthritis in the child presenting with acute non-traumatic limp. A systematic review

BACKGROUND

Septic arthritis is an uncommon but potentially significant diagnosis to be considered when a child presents to the emergency department (ED) with non-traumatic limp. Our objective was to determine the diagnostic accuracy of clinical findings (history and examination) and investigation results (pathology tests and imaging) for the diagnosis of septic arthritis among children presenting with acute non-traumatic limp to the ED.

METHODS

Systematic review of the literature published between 1966 and June 2019 on MEDLINE and EMBASE databases. Studies were included if they evaluated children presenting with lower limb complaints and evaluated diagnostic performance of items from history, physical examination, laboratory testing or radiological examination. Data were independently extracted by two authors, and quality assessment was performed using the Quality Assessment Tool for Diagnostic Accuracy Studies 2 tool.

RESULTS

18 studies were identified, and included 2672 children (560 with a final diagnosis of septic arthritis). There was substantial heterogeneity in inclusion criteria, study setting, definitions of specific variables and the gold standard used to confirm septic arthritis. Clinical and investigation findings were reported using varying definitions and cut-offs, and applied to differing study populations. Spectrum bias and poor-to-moderate study design quality limit their applicability to the ED setting.Single studies suggest that the presence of joint tenderness (n=189; positive likelihood ratio 11.4 (95% CI 5.9 to 22.0); negative likelihood ratio 0.2 (95% CI 0.0 to 1.2)) and joint effusion on ultrasound (n=127; positive likelihood ratio 8.4 (95% CI 4.1 to 17.1); negative likelihood ratio 0.2 (95% CI 0.1 to 0.3)) appear to be useful. Two promising clinical risk prediction tools were identified, however, their performance was notably lower when tested in external validation studies.

DISCUSSION

Differentiating children with septic arthritis from non-emergent disorders of non-traumatic limp remains a key diagnostic challenge for emergency physicians. There is a need for prospectively derived and validated ED-based clinical risk prediction tools.

Existing and emerging methods of diagnosis and monitoring of pediatric musculoskeletal infection

Methods of diagnosing and monitoring pediatric musculoskeletal infections are rapidly evolving. Key serologic tests are typically used in screening patients with suspected infections, and remain an integral part of the initial work-up. Synovial studies from arthrocentesis in possible septic arthritis, and source-specific cultures have been the foundation of our treatment algorithm. Given the prevalence of soft tissue abscesses and osteoarticular infections, advanced imaging is an advantageous tool. More affordable use and expanded access to MRI has made it a valuable adjunct to clinical picture and existing tests in order to comprehensively visualize the extent of musculoskeletal infections in children. Ongoing validation for criteria to help determine the patients that stand to benefit the most from MRI, even when surgical intervention may be delayed, remains of significant clinical interest. Given the rates of culture-negative infections, and the need for timely diagnosis, new diagnostic techniques are always being considered. The search for more accurate biomarkers, and technology such as Whole genome sequencing (WGS) and next-generation sequencing (NGS) that can rapidly identify pathogens of all types of phyla based on a small sample of DNA, has promising clinical implications. While once novel and prohibitively expensive, these tests are now being applied in university and tertiary care centers in certain scenarios. Applying these techniques to pediatric musculoskeletal will require a large change in lab workflow and training. However, the benefits of acquiring diagnostic information along with will make them a superior tool in our arsenal of diagnostic tests.

Current Variation in Joint Aspiration Practice for the Evaluation of Pediatric Septic Arthritis

Pediatric septic arthritis (SA) is a condition that can be associated with significant morbidity. Although previous research has been on predictive care pathways, scrutiny of the literature continues to reveal wide differences in the patient evaluation and management. The purpose of this study was to define the differences in joint aspiration for the evaluation of pediatric SA across pediatric tertiary care institutions in the United States.

Septic arthritis in children: Updated epidemiologic, microbiologic, clinical and therapeutic correlations

BACKGROUND

Septic arthritis (SA) is an infection characterized by significant epidemiologic and microbiologic differences between developed and developing regions and between age groups.

OBJECTIVES

To determine the epidemiologic, clinical, microbiologic and therapeutic aspects of pediatric SA in Southern Israel.

METHODS

A retrospective case-series study based on the records of children <16 years of age admitted with SA at Soroka Medical Center, Beer-Sheva, during 2006-2013.

RESULTS

189 patients were enrolled. There were 119 (63%) Bedouin and 70 (37%) Jewish children. The knee (39.7%), hip (28%) and ankle (13.8%) were the most commonly involved joints. Blood and/or synovial fluid cultures were positive in 48 (25.4%) patients. Overall SA incidence among children <16 years and <5 years was 11.7 and 25.4/100,000, respectively, without changes throughout the study period. SA incidence among Bedouin children was higher than among Jewish children (15.4 vs. 8.3/100,000 cases). Staphylococcus aureus was the most commonly isolated pathogen (18, 19.5% of all patients), followed by Kingella kingae (10, 5.3%)-(37.5% and 20.8% among culture-positive patients, respectively). The number of children with culture-positive SA that required surgery was higher than those with culture-positive SA treated conservatively (P < 0.001). Hospitalization was longer in children treated surgically than in those treated conservatively (P < 0.001).

CONCLUSION

This study is the largest single-center series on pediatric SA published in the last five years and provided an updated picture on incidence and the microbiologic, clinical and therapeutic aspects of pediatric SA in Southern Israel. The study supports a regional presentation pattern of SA and may guide its therapeutic management.

Septic Arthritis of the Hip in Children: A Critical Analysis Review

Septic arthritis of the hip is a common and potentially devastating condition in children. Septic arthritis is most commonly caused by Staphylococcus aureus, but other pathogens should be considered on the basis of patient age and presence of risk factors. Diagnosis of septic arthritis is based on history and physical examination, laboratory tests, radiographs, ultrasound, and arthrocentesis. Treatment comprises empiric antibiotics and joint debridement, and antibiotics are subsequently tailored on the basis of culture data, local resistance patterns, and clinical response. Late sequelae of septic arthritis include osteonecrosis, chondrolysis, growth disturbance, subluxation or dislocation, and progressive ankylosis. Surgical treatments to address these issues have been described.

Pediatric Septic Arthritis of the Knee: Predictors of Septic Hip Do Not Apply

BACKGROUND

The early diagnosis of pediatric septic arthritis is paramount to the prevention of long-term sequela. The purpose of this study is to investigate if the commonly used criteria developed by Kocher and colleagues for hip septic arthritis can be used for screening children with suspected septic knee.

METHODS

We retrospectively reviewed the charts of patients under the age of 19, between June 2002 to June 2017, who presented to a major tertiary-care children's hospital with septic knee. Diagnostic criteria included either a positive synovial culture from the knee, synovial white blood cell (WBC)>50,000 cells/mm, or synovial WBC count >25,000 cells/mm and clinical agreement of diagnosis from Infectious Disease and Orthopaedic colleagues. Collected data included the initial criteria described by Kocher and colleagues: history of fever, non-weight-bearing, erythrocyte sedimentation rate, and serum WBC as well as a recently modified criterion: C-reactive protein. Univariate analysis was used to determine the quality of these variables in ruling out septic knee.

RESULTS

One hundred four patient charts were found to meet our inclusion criteria demonstrating C-reactive protein>20 mg/L (75%), fever (65%), non-weight-bearing status (64%), erythrocyte sedimentation rate>40 mm/h (60%), and WBC>12,000 cells/mm (49%). With the 25 different combinations of these predictors adjusted for, in an escalating manner, 0 predictors suggested a sensitivity of 0.02, 1 predictor a sensitivity of 0.06, 2 predictors a sensitivity of 0.2, 3 predictors a sensitivity of 0.32, 4 predictors a sensitivity of 0.3, and 5 predictors a sensitivity of 0.11.

CONCLUSIONS

According to the Kocher criteria of the hip, at 3 or more criteria the probability of septic arthritis becomes 93% with a sensitivity of 0.84 provoking many physicians to use this cutoff in their assessment of hip pain. This study suggests that if these criteria were applied to the knee, 52% of septic knee cases could be missed. There is a need for further investigation of specific criteria of the knee as the markers of the hip septic arthritis are not necessarily applicable in the knee.

LEVEL OF EVIDENCE

Level III.

Synovial fluid cell counts and its role in the diagnosis of paediatric septic arthritis

PURPOSE

Clinical presentation of paediatric septic arthritis (SA) can be similar to other joint pathologies. Despite potential for infection in all major joints, most diagnostic criteria are based on values from the hip. This study identifies the best joint aspirate values in diagnosing SA in all joints.

METHODS

In all, 166 patients who underwent 172 joint aspirations at the authors' institution between 01 September 2004 and 01 September 2014 were retrospectively identified. Recorded measures included age, sex, duration of symptoms, fever history, weight-bearing status, aspiration results, serum results and antibiotic administration. Patients were placed in the following four categories: 'culture confirmed SA' (C-SA), 'suspected SA' (S-SA), 'Other' and 'Other-rheumatologic' (Other-R), a subcategory of 'Other'.

RESULTS

Most common sites of aspiration were the knee (55%) and hip (29%). Diagnostic grouping was as follows: C-SA = 44, S-SA = 45, Other = 83 (Other-R = 21). Fever and non-weight-bearing prior to admission were useful predictors of SA, though in C-SA patients, 21% did not have a fever and 23% could weight bear at the time of admission. Aspirate white blood cell (WBC) count was significantly greater in both C-SA (92 000 cells/hpf) and S-SA (54 000) than in Other (10 000) and Other-R (18 000) patients. The percentage of polymorphonuclear (%PMN) was also significantly greater in C-SA (81.1%) and S-SA (80.9%) than in Other (57.9%) and Other-R (63.3%).

CONCLUSION

Joint aspirate values, especially %PMN, are valuable in diagnosing SA. Additionally, antibiotics pre-aspiration did not affect %PMN, facilitating subsequent diagnosis of infection. Lastly, while aspirate WBC count was a valuable indicator of SA, this finding is not as definitive as previous research suggests.

LEVEL OF EVIDENCE

IV Case Series.

Septic arthritis of the pediatric hip: update on diagnosis and treatment

PURPOSE OF REVIEW

To review the clinical diagnosis, management and natural history of septic arthritis of the hip (SAH) in the pediatric patient, and to highlight new information that may improve the management of these patients.

RECENT FINDINGS

The basics of management of possible pediatric SAH have remained largely unchanged for generations. New questions have been raised regarding the role and timing of advanced imaging (MRI) in the evaluation of patients with possible SAH. Published criteria have been derived to guide the need for MRI studies in these patients. Validation of these guidelines continues. Recent reviews have highlighted the possibility of Lyme disease as a potential cause of monoarticular pediatric hip pain. The role of PCR technology in the diagnosis and management of SAH remains unclear at this time.

SUMMARY

The child with a limp remains a common and urgent clinical concern. There may be expanded roles for MRI and PCR to better diagnose and treat the involved joint itself, as well as any associated nonarticular area of infection. Lyme disease should remain on the list of possible differential diagnoses in this population, particularly in geographic areas where the disease vector is known to be endemic.

Lyme Arthritis of the Pediatric Elbow: A Case Series

Most patients with untreated Lyme disease will experience joint symptoms. Owing to their resemblance in clinical presentation, Lyme arthritis and septic arthritis are often difficult to differentiate. However, their treatment is different. The elbow is rarely the first joint to present with symptoms. Therefore, Lyme disease is not commonly included in the differential diagnosis for children presenting with isolated elbow pain. The authors report 4 cases of monoarticular Lyme arthritis presenting in the elbow. There was an average delay of diagnosis of 4.75 days. Three cases were treated with oral antibiotics alone; 1 case was treated with unnecessary surgery due to uncertainty of the diagnosis and the delay in the laboratory performing the Lyme serology tests. The authors strongly recommend that Lyme serology be performed on an emergent basis to prevent unneeded surgery. [Orthopedics. 2018; 41(4):e511-e515.].

Hip Synovial Fluid Cell Counts in Children From a Lyme Disease Endemic Area

BACKGROUND

Patients with septic hip arthritis require surgical drainage, but they can be difficult to distinguish from patients with Lyme arthritis. The ability of synovial fluid white blood cell (WBC) counts to help discriminate between septic and Lyme arthritis of the hip has not been investigated.

METHODS

We assembled a retrospective cohort of patients ≤21 years of age with hip monoarticular arthritis and a synovial fluid culture obtained who presented to 1 of 3 emergency departments located in Lyme disease endemic areas. Septic arthritis was defined as a positive synovial fluid culture result or synovial fluid pleocytosis (WBC count ≥50 000 cells per µL) with a positive blood culture result. Lyme arthritis was defined as positive 2-tiered Lyme disease serology results and negative synovial fluid bacterial culture results. All other patients were classified as having other arthritis. We compared median synovial fluid WBC counts by arthritis type.

RESULTS

Of the 238 eligible patients, 26 (11%) had septic arthritis, 32 (13%) had Lyme arthritis, and 180 (76%) had other arthritis. Patients with septic arthritis had a higher median synovial fluid WBC count (126 130 cells per µL; interquartile range 83 303-209 332 cells per µL) than patients with Lyme arthritis (53 955 cells per µL; interquartile range 33 789-73 375 cells per µL). Eighteen patients (56%) with Lyme arthritis had synovial fluid WBC counts ≥50 000 cells per µL. Of the 94 patients who underwent surgical drainage, 13 were later diagnosed with Lyme arthritis.

CONCLUSIONS

In Lyme disease endemic areas, synovial fluid WBC counts cannot always help differentiate septic from Lyme arthritis. Rapid Lyme diagnostics could help avoid unnecessary operative procedures in patients with Lyme arthritis.

Patient Factors Associated With Methicillin-Resistant Staphylococcus aureus Septic Arthritis in Children

Staphylococcus aureus is the most common causative organism in pediatric septic arthritis, with methicillin-resistant Staphylococcus aureus (MRSA) being responsible for a significant portion of these infections. Early identification and initiation of proper treatment may improve outcomes by minimizing potential morbidity. The purpose of this study was to identify variables obtained on initial patient presentation associated with MRSA septic arthritis. Sixteen factors were retrospectively evaluated in 109 consecutive pediatric patients diagnosed with culture-confirmed septic arthritis. Graphical and logistical regression analyses were employed to determine factors independently predictive of MRSA septic arthritis. Twenty-seven (25%) patients had MRSA and 82 (75%) had non-MRSA septic arthritis. C-reactive protein of 13.7 mg/L or greater, duration of symptoms of 4 days or more, heart rate of 126 beats per minute or greater, and absolute neutrophil count of 8.72×10³ cells/µL or greater were associated with MRSA septic arthritis. Ultimately, 98% of patients with 1 or no risk factors had non-MRSA and 96% of patients with MRSA septic arthritis had 2 or more positive risk factors. Elevated C-reactive protein, duration of symptoms, heart rate, and absolute neutrophil count are predictive of MRSA infection in the setting of pediatric septic arthritis and can be obtained on initial evaluation. In patients for whom there is concern for MRSA infection, this may guide more expedient treatment, such as early initiation of contact precautions and appropriate antibiotic therapy before culture results become available. [Orthopedics. 2018; 41(2):e277-e282.].

Distinguishing Pediatric Lyme Arthritis of the Hip from Transient Synovitis and Acute Bacterial Septic Arthritis: A Systematic Review and Meta-analysis

Objective

Lyme arthritis is an increasingly recognized clinical entity that often prompts orthopaedic evaluation in pediatric patients. While Lyme arthritis is most common in the knee, the clinical presentation of Lyme arthritis of the hip can be similar to both acute bacterial septic arthritis and transient synovitis. Accurately distinguishing these clinical entities is important since the definitive treatment of each is distinct. Because there is limited literature on monoarticular Lyme arthritis of the hip, the purpose of this study was to perform a systematic review and meta-analysis of clinical and laboratory parameters associated with Lyme arthritis (LA) of the hip and compare them to septic arthritis (SA) and transient synovitis (TS). 

Study design

A systematic review of the literature was performed using the following search terms, including the variants and plural counterparts “hip” and “Lyme arthritis.” A final database of individual patients was assembled from the published literature and direct author correspondence, when available. A previously published cohort of patients with hip transient synovitis or septic arthritis was used for comparative analysis. A comparative statistical analysis was performed to the assembled database to assess differences in laboratory and clinical variables between the three diagnoses. 

Results

Data on 88 patients diagnosed with Lyme arthritis of the hip was collected and consolidated from the 12 articles meeting inclusion criteria. The average age of patients presenting with Lyme arthritis was 7.5 years (± 3.5 years), the mean erythrocyte sedimentation rate (ESR), and the C-reactive protein (CRP) was 41 mm/hr and 3.9 mg/L, respectively. Peripheral white blood cell (WBC) count averaged 10.6 x 10⁹cells/L with the synovial WBC count averaging 55,888 cells/mm³. Compared to a previous cohort of patients with confirmed transient synovitis or septic arthritis, the 95% confidence interval for ESR was 21 - 33 mm/hr in those diagnosed with toxic synovitis (TS), 37 - 46 mm/hr for Lyme arthritis (LA), and 44 - 64 mm/hr for septic arthritis (SA). Synovial WBC counts (cells/mm³) 95% confidence intervals (CI) were 5,644 - 15,388 cells/mm³ for TS, 47,533 - 64,242 cells/mm³ for LA, and 105,432 - 260,214 cells/mm³ for SA. There was a statistically significant difference in the incidence of fever > 38.5^oC (P < 0.001) and refusal to bear weight (P < 0.01) between SA, LA, and TS.

Conclusions

Monoarticular Lyme arthritis can be a cause of hip pain in certain geographic areas and has clinical and diagnostic overlap with transient synovitis and acute bacterial septic arthritis. This study consolidates the available literature and represents the largest series of patients diagnosed with Lyme arthritis of the hip to date. We propose a diagnostic algorithm that serially incorporates ESR, followed by a synovial neutrophil count, when evaluating pediatric patients with an irritable hip in Lyme endemic areas. 

Pediatric Lyme Arthritis of the Hip: The Great Imitator?

BACKGROUND

Lyme arthritis (LA) of the hip can present similarly to septic arthritis (SA) and transient synovitis (TS). The primary purpose of this study was to determine clinical and laboratory parameters differentiating LA of the hip from SA or TS among children who had undergone hip aspiration during the evaluation of hip pain.

METHODS

This was a retrospective review of all patients who underwent hip aspiration for the evaluation of hip pain at a tertiary care children's hospital in a Lyme endemic area. Clinical and laboratory data were reviewed and comparative analyses were performed between those diagnosed with LA, SA, and TS. Independent samples t test, ANOVA, and χ test were used to compare clinical and laboratory variables as appropriate. Multivariable logistic regression was used to elucidate independent predictors of LA. Statistical significance was set at P<0.05.

RESULTS

Ninety-three hip aspirations (93 patients) were included in the final analysis. Seventeen patients were diagnosed with LA, 40 with SA, and 36 with TS. Multivariable logistic regression revealed febrile history (OR=16.3; 95% CI, 2.35-113.0) and increased peripheral white blood cell (WBC) count (OR=1.26; 95% CI, 1.01-1.58) to be significantly associated with increased odds of being diagnosed with SA versus LA. Increased erythrocyte sedimentation rate (ESR) was significantly associated with increased odds of being diagnosed with LA versus TS (OR=1.06; 95% CI, 1.02-1.10), whereas febrile history (OR=0.06; 95% CI, 0.01-0.49) and increased peripheral WBC count (OR=0.8; 95% CI, 0.65-0.98) were associated with decreased odds of LA.

CONCLUSIONS

Children presenting in a Lyme endemic area with an isolated hip effusion are more likely to have LA versus SA if they have no history of fever and a decreased peripheral WBC count. Compared with TS, patients with LA are more likely to have an elevated ESR. This study adds to existing knowledge because there are few investigations examining isolated LA of the hip.

LEVEL OF EVIDENCE

Level III-retrospective case-control study.

[Acute haematogenous osteomyelitis in children : Diagnostic algorithm and treatment strategies]

Acute haematogenous osteomyelitis (AHO) in children is a severe condition. A delay in diagnosis and insufficient treatment may result in deformities, chronicity and sepsis. Therefore a structured diagnostic workup has to be followed in order to diagnose or rule out osteomyelitis. To identify the causative agent for targeted antibiotic treatment, a bone biopsy or puncture should be performed. However, approximately 25% of cases are culture-negative even after biopsy. The knowledge of the typical age-dependent bacterial spectrum is essential for empirical antibiotic therapy. The principal causative organism is Staphylococcus aureus. Surgery is not routinely required in paediatric acute osteomyelitis but surgical intervention is indicated if an abscess is detected. Secondary septic arthritis is a serious complication which has to be treated immediately by surgical intervention. Nevertheless, complete regeneration can be expected in up to 80% of children with AHO.

Polymerase chain reaction detection of Kingella kingae in children with culture-negative septic arthritis in eastern Ontario

BACKGROUND

The bacterium Kingella kingae may be an under-recognized cause of septic arthritis in Canadian children because it is difficult to grow in culture and best detected using molecular methods.

OBJECTIVES

To determine whether K kingae is present in culture-negative joint fluid specimens from children in eastern Ontario using polymerase chain reaction (PCR) detection methods.

METHODS

K kingae PCR testing was performed using residual bacterial culture-negative joint fluid collected from 2010 to 2013 at a children's hospital in Ottawa, Ontario. The clinical features of children with infections caused by K kingae were compared with those of children with infections caused by the 'typical' septic arthritis bacteria, Staphylococcus aureus and Streptococcus pyogenes.

RESULTS

A total of 50 joint fluid specimens were submitted over the study period. Ten were culture-positive, eight for S aureus and two for S pyogenes. Residual joint fluid was available for 27 of the 40 culture-negative specimens and K kingae was detected using PCR in seven (25.93%) of these samples. Children with K kingae were significantly younger (median age 1.7 versus 11.3 years; P=0.01) and had lower C-reactive protein levels (median 23.8 mg/L versus 117.6. mg/L; P=0.01) than those infected with other bacteria.

CONCLUSIONS

K kingae was frequently detected using PCR in culture-negative joint fluid specimens from children in eastern Ontario. K kingae PCR testing of culture-negative joint samples in children appears to be warranted.

Aspirations of the ilium and proximal femur increase the likelihood of culturing an organism in patients with presumed septic arthritis of the hip

PURPOSE

To test the hypothesis that collecting material for culture from metaphyseal bone of the ilium and proximal femur at the time of a hip aspiration will increase the sensitivity to detect an infectious organism in patients with presumed septic arthritis of the hip.

METHODS

We retrospectively reviewed a series of 36 patients with presumed septic arthritis of the hip, based on clinical exam and serum inflammatory markers, who underwent aspirations of hip synovial fluid as well as blood from the ilium and proximal femur. Culture results from aspirates of synovial fluid and bone and tissue from capsule were compared to determine the sensitivities and specificities of a synovial aspirate alone versus synovial aspirate plus aspirates of the ilium and proximal femur to detect infection.

RESULTS

The sensitivity of hip synovial fluid aspirates to detect infection via positive culture was only 63 %, though this increased significantly to 100 % when the results of cultures of aspirates of the ilium and proximal femur were included. The specificities were equivalent in both modalities (≥90 %). We conclude that obtaining aspirates of the ilium and proximal femur at the time of hip synovial fluid aspiration increases the likelihood that the procedure will return an infectious organism.

CONCLUSION

Positive cultures from a child with a septic hip or peri-articular hip infection help to efficiently and effectively guide antibiotic treatment. The child with a septic hip or peri-articular hip infection and positive cultures is likely to receive more narrow-spectrum therapy, potentially decreasing the overuse of broad-spectrum antibiotics.

LEVEL OF EVIDENCE

DIAGNOSTIC STUDY LEVEL III: Development of diagnostic criteria on the basis of a series of non-consecutive patients (with universally applied reference "gold standard").

Polyarticular Septic Arthritis Caused by Haemophilus influenzae Serotype f in an 8-Month-Old Immunocompetent Infant: A Case Report and Review of the Literature

Background. The standard use of vaccinations against pathogens has resulted in a decreased incidence of musculoskeletal infections caused by these previously common bacterial pathogens. Consequently, the incidence of infections caused by atypical bacteria is rising. This report presents a case of septic arthritis caused by non-type b H. influenzae in a pediatric patient. Methods. We report a case of an infant with polyarticular septic arthritis caused by H. influenzae serotype f. A literature review was conducted with the inclusion criteria of case reports and studies published between 2004 and 2013 addressing musculoskeletal H. influenzae infections. Results. An 8-month-old female presented with pain and swelling in her right ankle and left elbow. The patient was diagnosed with septic arthritis and underwent incision and drainage. Wound and blood cultures were positive for Haemophilus influenzae serotype f. In addition to treatment with IV antibiotics, the patient underwent immunocompetency studies, which were normal. Subsequent follow-up revealed eradication of the infection. Conclusions. Haemophilus influenzae non-type b may cause serious invasive infections such as sepsis or septic arthritis in children with or without predisposing factors such as immunodeficiency or asplenia. Optimal treatment includes surgical management, culture driven IV antibiotics, and an immunologic workup.