Purpose or Case Report: Developmental dysplasia of the hip (DDH) is the designation given to a spectrum of structural changes in the developing hip. Ultrasound is the preferred imaging method for screening this condition in newborns and children under 1 year old. Pubofemoral distance (PFD) has been proposed as a new screening method for developmental dysplasia of the hip. The aim of this study is to assess the accuracy of PFD for developmental dysplasia of the hip using the Graf method as reference standard.
Methods & Materials: A prospective single-institution study with 935 hips from 412 children at elevated risk for DDH from 1 day to 9 months of age. The Graf method was performed for diagnosis and classification of the DDH. Hips were divided into two groups according to the Graf type gradation: Group I, considered normal (Graf types Ia, Ib and IIa); and Group II, considered dysplastic (Graf types IIb or greater). In each hip the PFD was measured and the statistical analysis was performed to assess its accuracy.
Results: The sensitivitie and specificities of the indice was analyzed through receiver operating characteristic (ROC) curves. The greater area under curve was 0,63, obtained with the cutoff 3,5 mm for PFD. With this cutoff, values of Sensibility and Specificity were respectively 64% (CI 95% 0,546; 0,726) and 63% (CI 95% 0,597; 0,663).
Conclusions: The cut-off level for instability about PFD is not clear and needs to be established. In our study the cut-off value should be set lower at 3.5 mm.