Relationship between the clinical characteristics of osteomyelitis and the finding of extraosseous fat on MRI in pediatric patients.

BACKGROUND: MRI is frequently utilized to evaluate patients for osteomyelitis. The findings of intramedullary and extramedullary fat globules as well as extramedullary fat-fluid levels can help improve the specificity of MRI for this diagnosis.

OBJECTIVE: To correlate these MRI findings with the clinical characteristics in children with osteomyelitis.

MATERIALS AND METHODS: A retrospective electronic medical record search for pediatric patient charts from March 2004 to November 2009 that contained the word "osteomyelitis" in the "principal diagnosis" portion of the international classification of disease (ICD) billing code. Each electronic chart was reviewed. MRI examinations of selected children were reviewed by a pediatric radiologist, a general radiologist and a transitional year resident.

RESULTS: A total of 10 patients/11 MRI studies were included. Five of the 11 had the MRI finding of extramedullary globular fat signal. There was a significantly increased likelihood of seeing this finding in children of pubertal or postpubertal age compared to those of prepubertal age (p < 0.05).

CONCLUSION: This study provides evidence that the MRI finding of extramedullary fat globules in children with acute osteomyelitis is associated with the clinical characteristic of being within or above the age range for puberty.