Ferdia Aidan Gallagher BMBCh, Presenter: Research funded, General Electric Company

Brendan Chiat Koo MBBCh, Abstract Co-Author: Nothing to Disclose

Philip William Bearcroft MD, Abstract Co-Author: Nothing to Disclose

To review the radiological and microbiological results of pediatric hip ultrasounds and subsequent arthrocentesis performed in our department over a five-year period.

All hip ultrasounds performed over a five-year period on 2 to 10 year-olds presenting to the emergency department with a painful hip were reviewed retrospectively. Those showing an effusion and those that subsequently underwent aspiration were recorded. The microscopy and culture results for the aspirated joint fluid were assessed to determine the incidence of microbiologically-positive septic arthritis.

Of the 452 patients referred for ultrasound, 46% were found to be positive for an effusion. Of these, aspiration was successfully performed in 65% and failed in 13%. Only one (0.7%) was initially gram-stain positive but this later failed to culture an organism. A further sample was culture positive for staphylococcus aureus but in this case the initial gram-stain was negative and the admission white cell count was markedly elevated.

Irritable hip is a common cause for hospital admission and often poses a diagnostic challenge as it is important to exclude septic arthritis. Although ultrasound has been shown to have high sensitivity in diagnosing pediatric hip effusions, it cannot consistently differentiate transient synovitis from sepsis. There is a very wide range of values recorded in the literature for the incidence of septic arthritis in patients with features of a hip effusion on ultrasound: 2-70%. This may reflect varying selection criteria for ultrasound as well as the manner in which the diagnosis is subsequently confirmed. Our study demonstrates a very low incidence of culture-positive hip aspirates from a large cohort over a long time interval; the only positive case demonstrated abnormal serum markers for inflammation on admission. This study has not however addressed the issue of whether aspiration may provide symptomatic relief for patients with transient synovitis or be therapeutic for septic arthritis.

The results suggest that the diagnosis of septic arthritis may be excluded in the absence of abnormal inflammatory markers thus eliminating the need for an invasive investigation.

Gallagher, F, Koo, B, Bearcroft, P, Retrospective Five Year Review of the Outcome of Children Presenting with an Irritable Hip for Ultrasound and Arthrocentesis.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5006991.html