[Ultrasonography in the diagnosis and follow-up of hip pain in children].

Fifty-seven subjects aged 1.5-14 years (mean: 6.5; standard deviation: 3.3) complaining of hip pain and/or limp underwent clinical, US and radiologic examinations on admission and after variable time intervals. Twenty-eight of them were found to be affected with transient synovitis, 2 with rheumatic fever, 2 with slipped capital femoral epiphysis and 5 with Legg-Calvè-Perthes disease. The extant 20 subjects with normal US and X-ray findings were diagnosed as having irritable hip without effusion. No false-negative results were obtained from US (100% sensitivity), whereas X-ray provided false-negative results in 28 of 37 patients with hip disorders other than irritable hip without effusion (24.3% sensitivity). No significant difference in the extent of hip joint effusion was found at US between the various groups. In the transient synovitis group, joint effusion was apparent on X-ray image in 3 of 28 patients, in whom the effusion was significantly more severe than in the extant 25 patients. Capsular joint effusion resolved more rapidly in transient synovitis than in Legg-Calvè-Perthes disease. The patients with both rheumatic fever and transient synovitis exhibited the most rapid onset of symptoms. On the basis of our results, we suggest that each patient complaining of hip pain and/or limp should undergo US first and that X-rays be performed second, in selected cases only.