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The natural history of sonographic developmental dysplasia of the hip was determined in a population-based study in which 5170 infants were screened by ultrasound using Graf's method. Of the normal hips at the age of 1 month, 99.6 were still normal at the age of 3 months. Of the immature type IIaIIa and type IIa− hips, if untreated, 95.3 and 84.4 had become normal, respectively. Of the infants with type IIc, D and IIIIV hips at the age of 1 month 70, 58.3 and 90.9 were treated, respectively. This study shows that normal hips remain normal in nearly 100 of cases, but development to abnormality is possible. It shows also that most of the immature hips at the age of 1 month become normal without treatment. Although treatment seems to be indicated in the majority of sonographically abnormal hips, the occurrence of overtreatment could not be excluded in our study.

In this prospective study, 41 dislocated hips in 40 patients were classified according to Graf's sonographic classification. Of them, 29 hips were Graf type III and 12 hips Graf type IV. All were treated in a Pavlik harness to relocate the dislocated hip dynamically. In type III hips, this was successful in 97 and 50 in type IV hips. We conclude that Graf's classification in dislocated hips has prognostic significance in treatment with the Pavlik harness.