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Septic arthritis in children: frequency of coexisting unsuspected osteomyelitis and implications on imaging work-up and management.

OBJECTIVE
Osteomyelitis and septic arthritis clinically present at any age with overlapping signs and symptoms. The purposes of this study were to evaluate the demographic distribution of septic arthritis and osteomyelitis in children and to explore optimal imaging guidelines for these patients.


MATERIALS AND METHODS
We performed a retrospective study of children up to 18 years old who were treated for osteomyelitis or septic arthritis between January 2011 and September 2013. All patients underwent MRI without previous intervention. Studies were reviewed to determine the incidence of septic arthritis or superimposed osteomyelitis. The reference diagnosis was based on the combined review by the orthopedic surgeon and infectious disease notes, discharge summary, operative report, and MRI examination.


RESULTS
One hundred sixty-two children who underwent 177 MRI examinations were diagnosed with acute musculoskeletal infection. One hundred three patients were included in the septic arthritis category, of whom 70 (68%) had septic arthritis with osteomyelitis. Seventy-four (42.1%) patients had isolated osteomyelitis without septic arthritis. Children under 2 years old were more likely to have septic arthritis (either isolated or with osteomyelitis) than isolated osteomyelitis compared with older children (p = 0.0003).


CONCLUSION
In children who underwent MRI for suspected musculoskeletal infection, septic arthritis was more prevalent in children under the age of 2 years than in older children. However, both septic arthritis and osteomyelitis were found frequently in older children. Musculoskeletal infection imaging workup guidelines for children of all ages should address the frequent association of osteomyelitis and septic arthritis. We recommend that MRI should be used in the evaluation of suspected musculoskeletal infections in children, and the nearest joint should always be included to evaluate the extent of articular disease.