Manual versus digital radiographic measurements in acetabular dysplasia.

The intraobserver and interobserver variability of common radiographic measurements associated with hip dysplasia from plain and digital radiographs was assessed. Only the interobserver reliability of measuring Hilgenreiner's distance was found to be potentially clinically significant. The average Spearman correlation coefficients between groups were 0.81 acetabular index, 0.80 medial teardrop to medial metaphysis distance, and 0.77 Hilgenreiner's distance. The average difference between digital and plain radiographs was acetabular index 0.97 +/- 0.6 degrees, medial teardrop to medial metaphysis distance 0.5 +/- 0.56 mm, and Hilgenreiner's distance 0.41 +/- 0.78 mm. These values are clinically insignificant; therefore, digital radiographs are as reliable as conventional radiographs in assessing hip dysplasia.