Radiographic measurements in developmental dysplasia of the hip: reliability and validity of a digitizing program.

A fundamental goal of research in developmental dysplasia of the hip (DDH) has been the identification of radiographic quantitative factors predictive of long-term outcome. The rapid development of digital imaging modalities opens the possibility for more systematic, automated measurement of radiographs. The authors have developed a software program for the study of DDH that integrates a user interface to select, store, and edit prescribed landmarks on digital radiographs. These points are used to construct and display reference lines analogous to those commonly drawn on physical films. Measurements are stored as a printable text file and as a data record. The results of this study demonstrated very good intrarater and interrater reliability coefficients and intermethod validity coefficients for the digitizing program. If this program is added to a software reporting system, measurements can be done on a real-time basis and can be included in the patient's medical record.