Evaluation of Sacrum Morphology in Patient with Developmental Dysplasia of the Hip for Iliosacral Screw Fixation

Background: The purpose of this study was to evaluate the patients with developmental dysplasia of the hip (DDH) in terms of sacroiliac anatomy to proper placement of iliosacral screws. Methods: We retrospectively reviewed computed tomography (CT) records of 96 patients who were referred to our clinic. We mainly divided the patients into 2 groups; the iliosacral joint on the same side with DDH evaluated in the DDH group and on the contralateral side with DDH evaluated in the control group. The presence of the five qualitative characteristics of sacral dysplasia evaluated according to Route in both groups. The DDH group divided into three subgroups according to Hartofilakidis and Rout classifications. The cross-sectional area, length of the osseous corridor, coronal and vertical angulation evaluated in both groups. Results: : Sacral dysplasia observed %87.5 in the DDH group,%83.3 in the control groups. The DDH group also exhibited a significantly lower S1 cross-sectional area and S1 iliosacral screw length than the control group (p:0.018,p:0,027; respectively). No statistically significant difference was observed according to Hartofilakidis(p>0.05). According to Rout, the S1 iliosacral screw length of the normal and transient groups were found to be significantly higher than those of the dysplastic groups (p: 0.004, p:0.0001; respectively). The transient group also exhibited a significantly lower S1 iliosacral screw length than the normal group (p:0.001). There were no significant differences in S1 and S2 axial and coronal angulation, S2 cross-sectional area, S2 iliosacral screw length in the DDH groups (p>0.05) Conclusion: When iliosacral screw is planned for patients with unilateral DDH, surgeons should consider that there are high rates of dysplastic sacral changes, differences in S1 cross sectional area and iliosacral screw length compared to the opposite side, and asymmetric sacral dysplastic changes in the upper sacrum.