Reliability of Ultrasonography in the follow-up of Hip Dysplasia in Children above 2 Years of Age

Abstract

Purpose: the aim of the present study was to assess whether ultrasonography (US) was reliable in the follow-up of children above 2 years of age who had previously been treated for congenital or developmental hip dislocation or dysplasia (HD).

Material and Methods: As part of the routine follow-up, we examined 53 children (106 hips), aged 2–12 years (mean 6 years). Using US, the coverage of the femoral head was assessed by the distance from the lateral tangent of the ossified femoral head to the lateral bony acetabular rim (lateral head distance, LHD). the corresponding distance was measured on radiographs (LHDR). the radiographic femoral head coverage was assessed by the migration percentage (MP) and the center-edge (CE) angle.

Results: We found a good accordance between sonographic LHD and the radiographic parameters MP and CE in all age groups, indicating that femoral head coverage was reliably assessed by US. There was also a high correlation between LHD and LHDR (r=0.85). All hips with subluxation were detected by US. In 11 hips that appeared normal on US, but with dysplasia or uncertain findings by radiography, the condition spontaneously normalized in 9 out of 9 examined hips with further follow-up.

Conclusion: Because a reliable assessment of the hip is obtained, we recommend that US should be used as the primary imaging technique in the routine follow-up of children above 2 years of age with previous HD. Radiography should be omitted when US shows normal findings and is only needed when the US LHD is above the upper normal limit or the hip looks abnormal or suspicious by subjective evaluation.