Ultrasound as a diagnostic tool for femoral head containment disorders in children between one and 12 years of age

PURPOSE: Ultrasound has been used to diagnose hip dysplasia in neonates and to screen until the end of their first year. For older children, femoral head containment disorders such as developmental dysplasia of the hip, Legg-Calvé-Perthes disease or cerebral palsy are usually diagnosed with plain radiographs. The aim of the present study was to evaluate ultrasound in comparison with radiographic imaging in children up to age 12 years and to determine reference values for sonographic containment parameters. METHODS: Hip ultrasound and radiographic imaging were acquired on the same day and then compared. As a reference, normal acetabular angle and acetabulum head index were determined on radiographs. Lateral cartilage distance (LCD), lateral head distance (LHD) and femoral head extrusion angle (HA) were measured on ultrasound images. RESULTS: We included 96 patients with 167 healthy hips in the study. A total of 55 patients were female and 41 male. The mean age was 5.2 years (sd 3.3; 1.0 to 11.9). LCD(ultrasound), LHD(ultrasound) and HA(ultrasound) correlated significantly with radiographic parameters. The following ultrasound values were calculated as limits for impending loss of containment: LCD(ultrasound) ≥ 6.5 mm, LHD(ultrasound) ≥ 3.3 mm and HA(ultrasound) ≥ 27.6°. CONCLUSION: Ultrasound is a simple, radiation-free diagnostic tool to detect femoral head containment disorders, even in children older than one year. This study provides reference values for hip ultrasound in children up to 12 years. LEVEL OF EVIDENCE: III