Kocher Criteria Revisited in the Era of MRI: How Often Does the Kocher Criteria Identify Underlying Osteomyelitis?
BACKGROUND
The Kocher criteria are established clinical parameters that predict hip septic arthritis (SA) with a 93% or greater positive-predictive value when 3 or 4 variables are present. The incidence of osteomyelitis (OM) in these patients has not been reported. The purpose of this study is to evaluate the incidence of OM in patients who have 3 or 4 positive Kocher criteria.


METHODS
A total of 71 consecutive patients (mean age, 4.7 y) treated between January 2007 and July 2013 for suspected hip SA who had 3 or 4 positive Kocher criteria were retrospectively reviewed. The Kocher criteria variables include: non-weight-bearing status, fever>38.5°C, white blood cell>12 K, and erythrocyte sedimentation rate>40 mm/h. All patients underwent ultrasound (US) and magnetic resonance imaging as part of their workup.


RESULTS
There were a total of 71 patients with 3 or 4 positive Kocher criteria. Of these, 22.5% (n=16) had a diagnosis of SA and 47.9% (n=34) had a diagnosis of OM. Of the 71 patients, 52.1% (37/71) had a hip effusion on US. When an effusion was identified, 18.9% (7/37) had isolated SA, 18.9% (7/37) had isolated OM, and 24.3% (9/37) had combined SA and OM. When no effusion was identified, a total of 18/34 (52.9%) had underlying OM.


CONCLUSIONS
Patients with 3 or 4 Kocher criteria have a high incidence (47.9%) of OM. Even in patients with a hip effusion on US, the incidence of OM was equal to that of SA. These results suggest that the combination of Kocher criteria and US alone is not sufficient to make a diagnosis in patients presenting with hip irritability and consideration should be given to adding magnetic resonance imaging to their workup.


METHODS
Level III-retrospective chart review.
*Baylor College of Medicine†Texas Children's Hospital, Houston, TX.
Alex
A
Nguyen
J Herman
JH
Kan
George
G
Bisset
Scott
S
Rosenfeld
D002648:Child; D002662:Child Health Services; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D010019:Osteomyelitis / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014463:Ultrasonography