A Clinical Prediction Algorithm to Stratify Pediatric Musculoskeletal Infection by Severity

Admission Neutrophil-to-Lymphocyte Ratio Is Superior to WBC Count at Predicting the Presence and Severity of Pediatric Musculoskeletal Infection

BACKGROUND

Accurately determining the presence and severity of pediatric musculoskeletal infection (MSKI) is crucial for effective triage and treatment. Although the white blood-cell (WBC) count is often used as a marker for MSKI, we hypothesized that the use of the WBC count is limited by age-related variability in children. We proposed that the absolute neutrophil-to-lymphocyte ratio (NLR), which has less age-related variability, is a more reliable indicator for both diagnosing and assessing the severity of MSKI. The present study aims to compare the utility of WBC against that of the NLR, as well as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), for predicting MSKI presence and severity in children.

METHODS

A retrospective cohort study was conducted with use of a database of pediatric orthopaedic consultations for suspected MSKI between January 2013 and July 2022. Diagnoses were categorized as MSKI or no infection, and the severity of any present infection was stratified as local or disseminated. Admission laboratory values were collected. Statistical modeling was performed to assess the capabilities of the WBC, NLR, CRP, and ESR to diagnose MSKI and to assess infection severity, with cutoff thresholds established for clinical use.

RESULTS

This study included 650 patients (median age, 5.2 years; 63% male; 75% White). Of these, 247 patients had no infection, while 403 were diagnosed with an MSKI. Median WBC count, NLR, CRP, and ESR were all significantly higher in pediatric cases of confirmed MSKI. WBC was a poor predictor of infection severity, whereas NLR, CRP, and ESR each positively correlated with infection severity. At the time of admission, an NLR of 4 was highly specific for detecting the presence of infection, and an NLR of 5.8 was highly specific for predicting infection dissemination. CRP was the best predictor of both infection presence and severity, demonstrating the highest specificity and sensitivity, followed by NLR, which outperformed ESR and WBC.

CONCLUSIONS

Because of considerable age-related variability, the predictive value of the WBC count for pediatric MSKI presence and severity is limited. NLR, which is less affected by age-related variability, is superior at predicting MSKI severity. Although CRP remains the benchmark, the NLR offers a valuable alternative to the WBC. Our study provides a comparative framework for these biomarkers, enhancing MSKI assessment across various clinical settings.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Multicenter Retrospective Analysis of 702 Pediatric Cases of Bone and Joint Infections: Definition of Clinical and Biological Features to Discriminate K. kingae, S. aureus, and Other Bacterial Infections

This study aimed to identify key differences between K. kingae infections and those caused by S. aureus or other pathogens. Differentiating these infections is crucial due to their nonspecific clinical presentations and overlapping laboratory and radiological findings, particularly when isolates are unavailable. We retrospectively analyzed data from 702 pediatric patients with bone and joint infections from 2010 to 2023 across two hospitals. The most common diagnoses were osteomyelitis (35.3%) and arthritis (29.6%), with fever present in 46.0% of cases. Pathogen identification showed K. kingae (40.9%) and S. aureus (36.5%) as the most frequent. Patients with K. kingae were significantly younger (median age 1.5 years) than those with S. aureus (10.4 years) or other pathogens (6.8 years) (p < 0.001). Fever was more common in S. aureus (64.3%) and other pathogens (57.5%) than in K. kingae (26.4%) (p < 0.001). CRP levels were lower in K. kingae infections (median 1.5 mg/dl) compared to S. aureus (6.1 mg/dl) and other pathogens (5.0 mg/dl) (p < 0.001). K. kingae infections were predominantly treated with penicillin-clavulanate and had shorter treatment durations and lower sequelae rates (2.3%) compared to other pathogens (19.0%). These findings emphasize K. kingae's distinct clinical profile and milder course compared to S. aureus and other pathogens.

Navigating the Enigma of Pediatric Musculoskeletal Infections: A Race Against Time

Musculoskeletal infection (MSKI) in children is a critical condition in pediatric orthopedics due to the potential for serious adverse outcomes, including multiorgan dysfunction syndrome, which can lead to death. The diagnosis and treatment of MSKI continue to evolve with advancements in infectious organisms, diagnostic technologies, and pharmacologic treatments. It is imperative for pediatric orthopedic surgeons and medical teams to remain up to date with the latest MSKI practices.

CRP Predicts the Need to Escalate Care After Initial Debridement for Musculoskeletal Infection

BACKGROUND

Musculoskeletal infections (MSKIs) are a major cause of morbidity in the pediatric population and account for nearly 1 in every 10 consultations with a pediatric orthopaedic provider at a tertiary care center. To prevent or deescalate the risk of adverse medical and musculoskeletal outcomes, timely medical intervention in the form of antibiotics and potential surgical debridement is required. While there have been numerous studies indicating the value of laboratory testing during the initial workup of a child with MSKI, few studies to date have examined the utility of longitudinal assessment of laboratory measures in the acute setting to monitor the efficacy of antibiotic therapy and/or surgical intervention. The purpose of this investigation was to retrospectively determine whether measuring changes in the inflammatory response could indicate the need for escalated care. Specifically, this study examined the hypothesis that serial measurements of C-reactive protein (CRP), immediately preoperatively and 2 days after surgical debridement, could predict the need for medical (change in antibiotics) or surgical (additional debridement) escalation.

METHODS

Retrospective review of pediatric patients undergoing operative debridement for the treatment of MSKI between September 2009 and December 2015 from whom laboratory data (CRP) was obtained preoperatively and at postoperative day (POD) 2. Patient demographics, the need for escalated care, and patient outcomes were evaluated.

RESULTS

Across 135 pediatric patients, preoperative CRP values >90 mg/L and a positive change in CRP at POD2 effectively predicted the need for escalation of care after initial surgical debridement (Area under the Receiver Operator Curve: 0.883). For each 10-unit increase in preoperative CRP or postoperative change in CRP, there was a 21% or 22% increased risk of needing escalated care, respectively. Stratification by preoperative CRP >90 mg/L and change in CRP postoperatively likewise correlated with increased rates of disseminated disease, percent tissue culture positivity, length of stay, and rate of adverse outcomes.

CONCLUSIONS

This study demonstrates the utility of serial CRP to assess the need for escalated care in patients being treated for MSKI. As serial CRP measurements become standard of practice in the acute setting, future prospective studies are needed to optimize the timing of CRP reassessment during inpatient hospitalization to prognosticate patient outcomes, weighing both improvements of patient care and clinical burden.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

D-dimer may aid in the diagnosis of pediatric musculoskeletal infections: a prospective study

Musculoskeletal infections, including septic arthritis, osteomyelitis, and soft tissue infections, are critical morbidity factors for children and adolescents. This study investigated the role of D-dimer levels for diagnosing childhood musculoskeletal infections. This single-center prospective study was initiated in April 2020 following approval from the local ethics committee. The study included 54 children, divided into the infection group ( n = 21), comprising patients who underwent surgical treatment for childhood musculoskeletal infections and had macroscopically visible purulent discharge during surgery, and the control group ( n = 33), comprising healthy children. In the infection group, the mean values of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), plasma D-dimer, and white blood cell (WBC) were 39.42 ± 27.00 mm/h, 101.50 ± 76.90 mg/l, 2.34 ± 2.59 mg/l, and 15.55 ± 6.86 × 10 9 /l, respectively. On comparison, the infection group showed higher levels of WBC, CRP, ESR, D-dimer, and neutrophil-to-lymphocyte ratio than the control group. When the D-dimer cutoff value of 0.43 mg/l was taken, it was observed that it had 95.2% sensitivity and 81.8% specificity. The area under curve (AUC) of the above-mentioned parameters calculated via receiver operating characteristic curves showed CRP levels as the optimum predictor of childhood musculoskeletal infections, followed by the ESR, plasma D-dimer, and WBC levels in descending order (AUC: 0.999, 0.997, 0.986, and 0.935, respectively). D-dimer is another test, which in combination with other conventional established tests (CRP and ESR) can be helpful in diagnosis of pediatric infection. We recommend the addition of D-Dimer to ESR, CRP, and WBC as a first-line investigation in cases with suspected pediatric musculoskeletal infections.

Novel Uses of Traditional Algorithms for Septic Arthritis

BACKGROUND

Pediatric musculoskeletal infection (MSKI) is a bacterial infection of the bone, joint, and/or muscle that can be difficult to diagnose. The Kocher and Caird algorithms were developed to distinguish septic arthritis (SA) from transient synovitis (TS) in the hip. These algorithms have been applied to all patients presenting with painful, swollen monoarticular joints regardless of suspicion for SA. The aim of this analysis was to assess the test performance of Kocher and Caird to distinguish MSKI among all pediatric patients presenting with monoarticular joint pain. A secondary aim was to validate the original algorithms.

METHODS

We conducted a secondary analysis of a prospective cohort study evaluating the test performance of procalcitonin for suspected SA in a pediatric emergency department. Patients aged 0 to 16 years old who presented with a painful or swollen monoarticular joint were considered for enrollment. We compared the test performance of the traditional algorithms in an expanded population of MSKI versus alternate joint pain using sensitivity, specificity, and area under the curve (AUC). As a sensitivity analysis, missing data for predictors like temperature, erythrocyte sedimentation rate, C-reactive protein, and inability to bear weight were multiply imputed using the Stata program, mi impute, for changed equations.

RESULTS

The Caird algorithm had better test performance compared to the Kocher in all populations. Both algorithms were most discriminative in comparing SA to TS in all joints (AUC: 0.84 Caird and 0.75 Kocher). However, the Caird criteria performed almost as well discriminating MSKI from other causes of monoarticular joint pain in all joints (AUC: 0.79; 95% confidence interval: 0.72, 0.85) and nonhip joints (AUC: 0.80; 95% confidence interval: 0.71, 0.88).

CONCLUSION

Based on the findings of this study, it is clinically reasonable to apply the Caird algorithm to pediatric patients presenting with monoarticular joint pain of medium and large joints such as the knee, ankle, shoulder, elbow, and wrist, in addition to the hip.

LEVEL OF EVIDENCE

Level III-retrospective study of novel applications of SA algorithms.

Clinical Practice Guideline by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America: 2021 Guideline on Diagnosis and Management of Acute Hematogenous Osteomyelitis in Pediatrics

This clinical practice guideline for the diagnosis and treatment of acute hematogenous osteomyelitis (AHO) in children was developed by a multidisciplinary panel representing 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 AHO, including specialists in pediatric infectious diseases, orthopedics, emergency care physicians, hospitalists, and any clinicians and healthcare providers caring for these patients. The panel's recommendations for the diagnosis and treatment of AHO are based upon evidence derived from topic-specific systematic literature reviews. Summarized below are the recommendations for the diagnosis and treatment of AHO 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 (Grading of Recommendations Assessment, Development and Evaluation) approach. 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.

External Validation of an Algorithm to Predict Adjacent Musculoskeletal Infection in Pediatric Patients With Septic Arthritis

BACKGROUND

Septic arthritis (SA) remains a potentially morbid disease in the pediatric population. Magnetic resonance imaging (MRI) is the most sensitive tool for recognizing associated osteomyelitis and intramuscular abscess, but is a limited resource. The aim of this study is to externally validate a previously developed algorithm (Rosenfeld and colleagues) to predict adjacent infection in pediatric patients diagnosed with SA.

METHODS

We identified 120 children under 16 with presumed SA presenting to a tertiary referral center between 2008 and 2018. Patients without confirmed SA, those with insufficient data, and patients who did not receive perioperative MRI were excluded, leaving 53 patients. The previous algorithm suggests that patient age (above 4 y), C-reactive protein (>8.9 mg/L), platelet count (<310×10cells/µL), duration of symptoms (>3 d), and absolute neutrophil count (>7.2×10cells/µL) are risk factors for adjacent infection, with 3 or more variables signifying a "positive" result. Comparing against the gold standard of MRI, the accuracy of the algorithm was validated in terms of sensitivity, specificity, likelihood ratio (LR), and positive and negative predictive value. Discrimination and calibration of this algorithm have been assessed using receiver operating curve analysis and calibration plots.

RESULTS

The sensitivity and specificity of criteria from Rosenfeld algorithm were 73% and 44%, respectively. Receiver operating curve showed poor discrimination [area under the curve=0.54, confidence interval (CI): 0.26-0.83]. The positive predictive value was 55.9% and the negative predictive value was 63.1% with LR +1.23 (CI: 0.87-1.98) and LR -0.61 (CI 0.28-1.30). Only 53% of patients with 4 or more criteria had an adjacent infection on MRI. Examining our cohort, children with a positive MRI finding had higher mean C-reactive protein (77 vs. 122 mg/L, P=0.04) and were more likely to have waited >72 hours days between symptom onset and hospital presentation (P=0.03).

CONCLUSION

Although treatment algorithms are an attractive tool to guide clinicians and resource allocation, they need to take into account the local population characteristics before routine implementation.

LEVEL OF EVIDENCE

Level IV-retrospective cohort study.

The Heterogeneity of Pediatric Knee Infections: A Retrospective Analysis

BACKGROUND

Musculoskeletal infection is a major cause of morbidity in the pediatric population. Despite the canonical teaching that an irritable joint and signs of infection likely represent an infected joint space, recent evidence in the pediatric hip has demonstrated that alternative diagnoses are equally or more likely and that combinations of pathologies are common. The knee is the second most commonly infected joint in children, yet there remains a paucity of available data regarding the epidemiology and workup of the infected pediatric knee. The authors hypothesize that there is heterogeneity of pathologies, including combinations of pathologies, that presents as a potentially infected knee in a child. The authors aim to show the utility of magnetic resonance imaging and epidemiologic and laboratory markers in the workup of these patients.

METHODS

A retrospective review of all consults made to the pediatric orthopaedic surgery team at a single tertiary care center from September 2009 through December 2015 regarding a concern for potential knee infection was performed. Excluded from the study were patients with penetrating trauma, postoperative infection, open fracture, no C-reactive protein (CRP) within 24 hours of admission, sickle cell disease, an immunocompromised state, or chronic osteomyelitis.

RESULTS

A total of 120 patients were analyzed in this study. There was marked variability in pathologies. Patients with isolated osteomyelitis or osteomyelitis+septic arthritis were older, had an increased admission CRP, were more likely to be infected with Staphylococcus aureus, required an increased duration of antibiotics, and had an increased incidence of musculoskeletal complications than patients with isolated septic arthritis.

CONCLUSIONS

When considering a child with an irritable knee, a heterogeneity of potential underlying pathologies and combinations of pathologies are possible. Importantly, the age of the patient and CRP can guide a clinician when considering further workup. Older patients with a higher admission CRP value warrant an immediate magnetic resonance imaging, as they are likely to have osteomyelitis, which was associated with worse outcomes when compared with patients with isolated septic arthritis.

LEVEL OF EVIDENCE

Level III-retrospective research study.

Defining the volume of consultations for musculoskeletal infection encountered by pediatric orthopaedic services in the United States

Objective

Adequate resources are required to rapidly diagnose and treat pediatric musculoskeletal infection (MSKI). The workload MSKI consults contribute to pediatric orthopaedic services is unknown as prior epidemiologic studies are variable and negative work-ups are not included in national discharge databases. The hypothesis was tested that MSKI consults constitute a substantial volume of total consultations for pediatric orthopaedic services across the United States.

Study design

Eighteen institutions from the Children’s ORthopaedic Trauma and Infection Consortium for Evidence-based Study (CORTICES) group retrospectively reviewed a minimum of 1 year of hospital data, reporting the total number of surgeons, total consultations, and MSKI-related consultations. Consultations were classified by the location of consultation (emergency department or inpatient). Culture positivity rate and pathogens were also reported.

Results

87,449 total orthopaedic consultations and 7,814 MSKI-related consultations performed by 229 pediatric orthopaedic surgeons were reviewed. There was an average of 13 orthopaedic surgeons per site each performing an average of 154 consultations per year. On average, 9% of consultations were MSKI related and 37% of these consults yielded positive cultures. Finally, a weak inverse monotonic relationship was noted between percent culture positivity and percent of total orthopedic consults for MSKI.

Conclusion

At large, academic pediatric tertiary care centers, pediatric orthopaedic services consult on an average of ~3,000 ‘rule-out’ MSKI cases annually. These patients account for nearly 1 in 10 orthopaedic consultations, of which 1 in 3 are culture positive. Considering that 2 in 3 consultations were culture negative, estimating resources required for pediatric orthopaedic consult services to work up and treat children based on culture positive administrative discharge data underestimates clinical need. Finally, ascertainment bias must be considered when comparing differences in culture rates from different institution’s pediatric orthopaedics services, given the variability in when orthopaedic physicians become involved in a MSKI workup.

Knee orthopedic problems in newborns and infancy: a review

PURPOSE OF REVIEW

We present the reader with insight on the most common disorders of the knee in newborns and infants. Knee issues in this population may confuse the first contact physicians due to certain peculiarities of the immature immune system, small size and underdevelopment of joint anatomy. Data presented here are recent and significant, and something to bear in mind when caring for children of this age.

RECENT FINDINGS

With the advent of new diagnostic methods, a shift in the causative agent of pediatric knee infections has been noted. Minimally invasive methods such as arthrocentesis and arthroscopy are successfully employed in treatment of knee problems in newborns and infants. A trial of conservative therapy in congenital patellar instability can give good results, and obviate the need for surgery in some cases. Various syndromes that affect the knee have specific characteristics that need to be recognized early to avoid problems in the future.

SUMMARY

Although rare, knee problems in infants can and do occur. Their cause varies significantly and good outcomes require a multidisciplinary approach. Early diagnosis, referral and initiation of treatment protocols can significantly influence the fate of the joint and with it the patients' functional status for life.

Septic Arthritis of the Hip-Risk Factors Associated With Secondary Surgery

INTRODUCTION

Septic arthritis of the hip (SAH) is a common condition encountered by pediatric orthopaedic surgeons and is treated with arthrotomy and irrigation. Depending on the response to initial treatment, some patients require surgical treatment beyond the index procedure. The purpose of this study was to investigate risk factors for repeat surgical intervention after initial arthrotomy for presumed SAH.

METHODS

A multicenter retrospective review of all children who underwent surgical arthrotomy for presumed SAH over a ten-year period was conducted. Variables queried included demographics, clinical presentation, laboratory parameters, imaging, infecting organism, presence of osteomyelitis, and surgical interventions performed. Logistic regression was used to predict the risk of a second procedure. Chi-square was used to compare patients who required further surgery and those who did not.

RESULTS

One hundred and thirty-eight patients (139 hips) qualified for inclusion. The average age at initial surgery was 6.1 years (range, zero to 17 years), and 57% of the patients were male. Concomitant osteomyelitis was diagnosed in 55 cases (40%). An infecting organism was identified from 70 (50%) index intraoperative cultures, with Staphylococcus aureus infections (methicillin-resistant Staphylococcus aureus [MRSA], 27; methicillin-sensitive Staphylococcus aureus, 25) being the most frequent. Fifty-six patients (41%) underwent subsequent surgical intervention, at an average of 5.5 days (range, 2 to 95) from the index procedure. Independent risk factors for repeat surgical procedures included presenting C-reactive protein >10 mg/dL (P = 0.002) and presenting erythrocyte sedimentation rate >40 (P = 0.011). The odds of repeat surgical intervention were significantly increased by the presence of concomitant osteomyelitis (odds ratio, 3.4; P = 0.001) and positive index intraoperative cultures for MRSA (odds ratio, 1.19; P = 0.001). Preoperative MRI before the index procedure was not universal (73/138; 53%), and acquisition of preoperative MRI was not associated with secondary surgical intervention (P = 0.389).

DISCUSSION

Forty-one percent of children in this multicenter cohort underwent at least one repeat surgical procedure after the index arthrotomy for management of presumed SAH. Risk factors for return to the operating room include elevated initial erythrocyte sedimentation rate and C-reactive protein, infection with MRSA, and presence of osteomyelitis.

LEVEL OF EVIDENCE

Level 3, case-cohort series. Type of evidence, therapeutic.

Double-Edged Sword: Musculoskeletal Infection Provoked Acute Phase Response in Children

The acute phase response has a crucial role in mounting the body's response to tissue injury. Excessive activation of the acute phase response is responsible for many complications that occur in orthopedic patients. Given that infection may be considered continuous tissue injury that persistently activates the acute phase response, children with musculoskeletal infections are at markedly increased risk for serious complications. Future strategies that modulate the acute phase response have the potential to improve treatment and prevent complications associated with musculoskeletal infection.