Ultrasonography for diagnosis of slipped capital femoral epiphysis. Comparison with radiography in 9 cases.

In 7 of 8 patients with non-acute slipped capital femoral epiphysis, the slip was visualized by ultrasound. The mean epiphyseal displacement was 6.0 mm, measured on an anterior ultrasound scan. Grading of slip severity by ultrasound was consistent with the radiographic assessment. Two patients had a moderate hip joint effusion which did not affect the final outcome, whereas one patient with an acute slip had a pronounced effusion, and necrosis of the epiphysis occurred. The anteversion angles of the affected hips were reduced as compared to those of the normal hips. It was concluded that ultrasonography was reliable in detecting pronounced and mild degrees of epiphyseal slips, whereas minimal slips could be missed. The detection of hip effusion is important because a tamponade may cause vascular impairment of the epiphysis, unless aspirated.