Can Excessive Lateral Rotation of the Ischium Result in Increased Acetabular Anteversion? A 3D-CT Quantitative Analysis of Acetabular Anteversion in Children With Unilateral Developmental Dysplasia of the Hip

Background: The purposes of this study were to observe whether increased acetabular anteversion was a universal finding and whether excessive lateral rotation of the ischium was correlated with increased acetabular anteversion. Methods: We retrospectively reviewed 90 patients with unilateral developmental dysplasia of the hip (DDH), including 77 female patients and 13 male patients with an average age of 18 months (range, 6 to 60 mo). A total of 31 children were involved in the normal control group, including 14 girls and 17 boys with an average age of 21 months (range, 7 to 48 mo). The acetabular anteversion angle (AA), pubic relative length (PRL), ischiac relative distance (IRD), lateral rotational angle of the ischium (IA), and pubic rotational angle were compared between the affected hips and the unaffected hips in the unilateral DDH group and between the right hips and left hips in the normal control group. Results: No retroverted acetabulum was found in any hip. No significant differences in AA, IA, pubic rotational angle, IRD, and PRL were found between the left and right hips in the normal control group. However, the PRL was shorter in the affected hips than in the unaffected hips (P<0.05). The average IA, AA, and IRD in the affected hips were larger than that in the unaffected hips (P<0.05). The IA was positively correlated with AA and IRD in the DDH group. Conclusions: Increased acetabular anteversion in affected hips is a universal finding in unilateral DDH. The deficiency of the anterior wall in the acetabulum is not a unique reason for increased acetabular anteversion in unilateral DDH, because it is also correlated with excessive lateral rotation of the ischium.