Septic arthritis and osteomyelitis in pediatric patients represent true emergencies, and can quickly threaten life and limb. A high index of suspicion should be maintained, as these conditions often present with a subacute course of illness and vague signs and symptoms. Septic arthritis and osteomyelitis can occur concurrently, so suspicion for one should also prompt investigation for the other. The diagnostic evaluation should include blood work as well as samples from the infected joint or bone for culture. Management with antibiotics is a standard approach, but the duration of antibiotic therapy is controversial. This issue reviews the current literature and provides an evidence-based approach for the evaluation and management of pediatric patients with septic arthritis and osteomyelitis.
A 15-month-old boy presents to the ED with sudden onset of fever to 39.5°C (103.1°F), left knee swelling, and refusal to bear weight. His mother reports that the boy fell 2 days prior. He had a minor abrasion with some mild swelling to the left knee, but he was walking normally. This morning, the boy woke up with a fever, increased swelling and warmth of the left knee, and he refused to bear weight on the left leg. He is otherwise healthy, with no medical or surgical history. Aside from ibuprofen, he has not been given any other medication. His vital signs are notable for fever and tachycardia. During the physical examination, he refuses to walk and asks to be held. The right knee is normal, with normal range of motion. The left knee is erythematous, swollen, and has limited range of motion. You discuss with the mother that the differential diagnosis for this presentation is broad, and you would like to obtain some lab tests and imaging. You order acetaminophen for the persistent fever as well as a complete blood cell count, erythrocyte sedimentation rate, C-reactive protein, blood cultures, and plain radiography. You begin to think: Do you need to obtain additional imaging studies? What procedures should be performed?
A 4-year-old boy presents to the ED with intermittent fever, right leg pain, and difficulty walking the last 3 days. His parents report that the child has a history of sickle cell disease and takes folic acid and penicillin for infection prophylaxis. The patient has never had surgery. On physical examination, there is point tenderness over the right thigh and an area of overlying edema, and the boy's vital signs are within the normal limits for his age. You order a complete blood cell count, erythrocyte sedimentation rate, C-reactive protein, blood cultures, bone culture, and plain radiography. What special bacterial pathogen must be considered in this case? How does this affect antibiotic treatment?
Pediatric patients with septic arthritis (SA) and osteomyelitis (OM) commonly present to the emergency department (ED) with vague and nonspecific complaints, but fever and joint pain are usually present. Both diagnoses are true emergencies, and these conditions must be promptly diagnosed and treated.
Acute SA, or pyogenic arthritis, is a bacterial invasion of the synovium and joint space followed by an inflammatory process.1 SA can threaten both life and limb due to its potential for rapid destruction of the joint, causing significant disability within hours to days. Presenting symptoms vary based on age. Neonates and infants present with signs of septicemia, cellulitis, or fever without a source. Older children most commonly present with fever, joint pain, limited range of motion around the affected joint, and/or refusal to bear weight. SA is a surgical emergency, and it has a reported annual incidence of 1 to 37 cases per 100,000 children per year, although there is variation in different geographic areas.2 Peak incidence in the pediatric population is between 2 and 3 years of age, and boys are more commonly affected than girls.3
SA is often a hematogenous infection in children. The most commonly affected locations in the body are the large joints of the lower limbs (hip, knee, and ankle), accounting for approximately 80% of cases;3 the knee is the most commonly affected joint.4,5 SA most often affects previously healthy children, but certain groups are at higher risk for infection; these higher-risk individuals include patients who are immunocompromised (eg, diabetic patients, HIV-positive patients, patients who are on corticosteroid therapy), patients who were premature infants, or patients who have chronic illnesses requiring frequent phlebotomy.6
2. “The patient presented with vague/nonspecific pain. I didn’t consider a bone or joint infection.”
Both pediatric SA and OM present in a similar fashion, and the initial symptoms may be vague and nonspecific, so it is important to maintain a high index of suspicion. A thorough musculoskeletal examination should be completed and imaging should be obtained in order to fully assess the joint/bone involved.48,50
8. “I wanted to tailor the antibiotics to the specific microbial pathogen, so I decided to wait for culture results prior to starting antibiotic therapy.”
Ideally, empiric antibiotic therapy should be started after obtaining a reliable culture sample, but the initiation of antibiotics should not be delayed while awaiting results of culture samples. The antibiotics are geared toward the organisms known to be the most likely cause of SA and OM.22
10. “I instructed my patient to continue antibiotics at least until his symptoms improved.”
Incomplete antibiotic treatment duration and/or microbial coverage can attribute to antibiotic resistance and recurrence of symptoms. Both OM and SA require initial inpatient parenteral antibiotic therapy followed by oral antibiotic therapy lasting several weeks.6
Evidence-based medicine requires a critical appraisal of the literature based upon study methodology and number of subjects. Not all references are equally robust. The findings of a large, prospective, randomized, and blinded trial should carry more weight than a case report.
To help the reader judge the strength of each reference, pertinent information about the study is included in bold type following the reference, where available. In addition, the most informative references cited in this paper, as determined by the author, are highlighted.
Why to Use
Differentiating between SA and TS of the hip in children can be difficult. The Kocher criteria can be used to quickly identify subsets of patients who need urgent orthopedic consultation and those who can be observed.
When to Use
The Kocher criteria can be applied to all pediatric patients with an acutely irritable hip for whom SA and TS are in the differential diagnosis.
Abbreviations: CBC, complete blood cell; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; SA, septic arthritis; TS, transient synovitis.
Calvin Hwang, MD
Patients who meet none of the Kocher criteria can potentially be discharged; those who meet all 4 of the criteria require urgent orthopedic consultation for washout. Patients who meet some but not all of the Kocher criteria (1-3 predictors) may require hip arthrocentesis.
Diagnostic hip aspiration should be considered when there is a clinical concern for septic arthritis along with the presence of at least 1 predictor. If there is high clinical suspicion for SA, orthopedic consultation should not be delayed. Observation and/or discharge with close follow-up should be considered for well-appearing patients when there is low clinical suspicion for SA and no predictors are present.
In 1999, Kocher et al published a retrospective chart review of 282 patients who had been evaluated between 1979 and 1996 for an acutely irritable hip, and for whom the differential diagnosis included TS and SA. SA was diagnosed by a positive joint fluid culture or by a white blood cell (WBC) count in the joint fluid of ≥ 50,000 cells/mcL. Eighty-two patients were diagnosed with SA, while 86 were diagnosed with TS (defined as a WBC count of < 50,000 cells/mcL, with a negative joint fluid culture and resolution of symptoms without antimicrobial therapy).
The study identified 4 independent multivariate predictors for differentiation between SA and TS: (1) history of fever; (2) non–weight-bearing; (3) ESR > 40 mm/hr; and (4) serum WBC count > 12,000 cells/mcL. The probabilities for SA based on the number of predictors were as follows: 0 predictors = < 0.2%; 1 predictor = 3%; 2 predictors = 40%; 3 predictors = 93.1%; and 4 predictors = 99.6%.
In a 2004 study, Kocher et al prospectively applied the criteria to patients with an acutely irritable hip who had presented to a major tertiary-care children's hospital between 1997 and 2002. The cohort included 213 consecutive patients, 51 of whom whom were diagnosed with SA and 103 with TS. In this study, the probabilities for SA based on the number of predictors were as follows: 0 predictors = 2%; 1 predictor = 9.5%; 2 predictors = 35%; 3 predictors = 72.8%; and 4 predictors = 93%.
Other authors have retrospectively applied the Kocher criteria to their study populations. Luhmann et al (2004) found that having all 4 predictors yielded a probability for SA of just 59%, but they did not publish the rate of SA found when no predictors were present. Sultan et al (2010) retrospectively applied the Kocher criteria and found a predicted probability for SA of 59.9% when all 4 predictors were present, although the study was limited by having only 5 patients with SA, and no cases of SA in a patient with no predictors present.
Mininder S. Kocher, MD, MPH
Prakriti Gill, MD; Jennifer E. Sanders, MD
Richard M. Cantor, MD, FAAP, FACEP; Susan Fraymovich, DO
December 2, 2019
January 1, 2023
4 AMA PRA Category 1 Credits™, 4 ACEP Category I Credits, 4 AAP Prescribed Credits, 4 AOA Category 2-A or 2-B Credits. Specialty CME Credits: Included as part of the 4 credits, this CME activity is eligible for 4 Infectious Disease CME and 0.5 Pharmacology CME credits.
Date of Original Release: December 1, 2019. Date of most recent review: November 15, 2019. Termination date: December 1, 2022.
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