Emergency Department Management of Pediatric Septic Arthritis and Osteomyelitis

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Kocher Criteria for Septic Arthritis

• Introduction
• Points & Pearls
• Why and When to Use, and Next Steps
• Calculator Review Author
• Critical Actions
• Advice
• Evidence Appraisal
• Calculator Creator
• References
• Selected Abbreviations

Introduction

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Points & Pearls

• The Kocher criteria were derived to identify the variables that are important in distinguishing between septic arthritis (SA) and transient synovitis (TS).
• In the appropriate clinical setting, patients who fall on either probability extreme (0 criteria or 4 criteria) can be readily ruled in or out for SA.
• Patients with an intermediate probability of SA (1-3 criteria) may need further workup or intervention.
• Although the Kocher criteria did not perform as well in the validation study as in the original study, the prediction rule may still be clinically useful for patients falling on either extreme, with either 0 or 4 predictors.

Why and When to Use, and Next Steps

Calculator Review Authors

Calvin Hwang, MD

Critical Actions

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.

Advice

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.

Evidence Appraisal

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.

Calculator Creator

Mininder S. Kocher, MD, MPH

References

Original/Primary Reference

• Kocher MS, Zurakowski D, Kasser JR. Differentiating between septic arthritis and transient synovitis of the hip in children: an evidence-based clinical prediction algorithm. J Bone Joint Surg Am. 1999;81(12):1662-1670. 

Validation Reference

• Kocher MS, Mandiga R, Zurakowski D, et al. Validation of a clinical prediction rule for the differentiation between septic arthritis and transient synovitis of the hip in children. J Bone Joint Surg Am. 2004;86(8):1629-1635. 

Other References

• Luhmann SJ, Jones A, Schootman M, et al. Differentiation between septic arthritis and transient synovitis of the hip in children with clinical prediction algorithms. J Bone Joint Surg Am. 2004;86(5):956-962. 
• Sultan J, Hughes PJ. Septic arthritis or transient synovitis of the hip in children: the value of clinical prediction algorithms. J Bone Joint Surg Br. 2010;92(9):1289-1293.