Late presenting developmental dysplasia of the hip after a normal hip ultrasound at 6 weeks of age: A report of two cases.

Developmental hip dysplasia (DDH) is a paediatric condition in which the 'ball and socket' hip joint fails to form properly during infancy. The increased mechanical stress on the hip joint from DDH can contribute to the development of osteoarthritis during adulthood. Therefore, careful physical examination and imaging of all infants to diagnose DDH is critical to provide the best possible functional outcome. Ultrasonography (US) is a useful diagnostic test in providing a real-time evaluation and three-dimensional view of the hip in infants less than 4 months. In infants with a normal hip ultrasound, the risk of subsequent development of hip dysplasia at an older age and the need for further follow-up is assumed to be unnecessary. In the present study, we report 2 cases of late presenting DDH in infant girls born breech with a previous normal hip exam and normal hip ultrasound at 6 weeks of age.