[Coxitis fugax. The role of diagnostic imaging]

Between 1990 and 1996, 129 children (mean age 4.8 years) with hip pain were examined consecutively. In group I (n = 100, mean age 4.14 +/- 2.2), transient synovitis of the hip was diagnosed; group II (n = 29, mean age 7.3 +/- 2.1) showed the following diagnoses: Perthes' disease (n = 12), early slipped capital femoral epiphysis (n = 5), Meyer's dysplasia (n = 2), septic arthritis of the hip (n = 2), osteomyelitis of the acetabulum (n = 1), abscess of the psoas (n = 1), chondromatosis of the hip joint (n = 1), Ewing's sarcoma of the os pubis (n = 1), hip dysplasia (n = 1). Three patients who had synovitis developed Perthes' disease and were assigned to group II. The efficiency of ultrasound, scintigraphy and MRI as diagnostic tools was tested in the examination of painful hip. A capsular distension was present in 73 cases and showed a significant statistical difference (t-test, P < 0.001) in group I between affected and unaffected hips. There were no differences in the measurements of the epiphyseal and metaphyseal width in group I between the affected and the nonaffected side (t-test, P = 0.91, P = 0.57) and between the first sonographic evaluation at presentation and at the follow-up (t-test, P = 0.053, P = 0.75). MRI was performed, because of persistent joint effusion, in 10 cases in group I, and Perthes' disease was excluded. In group II the use of an MRI allowed the diagnosis in 89% of the cases. Sonographic examination, together with X-ray examination and serological testing, represent the first choices in the evaluation of a painful hip at presentation and in the follow-up of transient synovitis. MRI should always be performed when abnormalities are present at the clinical and sonographic examination, and when the X-ray does not allow a clear diagnosis.