Background <p>Emerging evidence suggests that developmental dysplasia of the hip involves not only localized acetabular dysplasia but also internal rotation of the entire innominate bone. Pemberton acetabuloplasty is widely used to improve acetabular coverage in walking-age children and generally yields favorable radiographic and clinical outcomes. However, the effect of this procedure on the global rotational alignment of the innominate bone has not been systematically investigated.</p> Methods <p>This retrospective comparative study included patients with a primary diagnosis of developmental dysplasia of the hip who underwent Pemberton acetabuloplasty at a tertiary care center between January 2011 and October 2021. Postoperative pelvic computed tomography scans were available for 20 unilateral and 12 bilateral cases, all of which were included in the analysis. In unilateral cases, the operated hemipelvis was compared with the contralateral side using paired t-tests to minimize inter-individual variability. Pelvic rotational parameters were further compared between unilateral and bilateral groups. Finally, data from all operated hips were pooled to evaluate the association between postoperative innominate rotational alignment and acetabular anteversion using Pearson’s correlation coefficient.</p> Results <p>In unilateral cases, the operated side demonstrated significantly greater external rotation of the upper pelvis compared with the contralateral side (mean difference, 3.3°; 95% confidence interval [CI], 0.7°–5.9°; <i>p</i> = 0.002), whereas acetabular anteversion and lower pelvic rotation did not differ significantly. No significant differences in pelvic rotational parameters or acetabular anteversion were observed between unilateral and bilateral procedures. When all operated hips were pooled for analysis, lower pelvic rotation demonstrated a moderate positive correlation with acetabular anteversion (<i>r</i> = 0.614, <i>p</i> &lt; 0.001), while upper pelvic rotation showed a weak but statistically significant correlation (<i>r</i> = 0.308, <i>p</i> = 0.042).</p> Conclusions <p>Postoperative excessive external rotation of the upper hemipelvis was observed following Pemberton acetabuloplasty, suggesting that structural alterations may extend beyond localized acetabular reshaping. These findings offer additional insight into the broader morphological changes associated with the procedure. Further prospective studies incorporating longitudinal imaging and objective functional assessment are warranted to better define the clinical significance of these structural alterations.</p> <i>Level of Evidence</i> <p>Level III, Retrospective comparative study.</p>