© 2020, Scoliosis Research Society.Purpose: The false acetabulum lies more laterally and posteriorly compared with the true acetabulum. Spatial orientation of the pelvis is significantly altered in patients with neglected high hip dysplasia. There has been no study to investigate how pelvic or sagittal spinal alignment change after true acetabulum gains function with hip arthroplasty. The aim of this study was to investigate the effect of total hip arthroplasty with femoral shortening on spinopelvic parameters in patients with neglected high hip dysplasia. Methods: Twenty patients with Crowe type 3 or 4 hip dysplasia, who underwent total hip arthroplasty with femoral shortening in our institution were evaluated preoperatively after completion of rehabilitation and return to their normal daily life. Sagittal alignment (sacral slope, pelvic incidence, global tilt, segmental lordosis, segmental kyphosis, GAP score) and coronal alignment angles (coronal tilt, Cobb angle) of patients were measured by two independent observers. Results: Twenty patients underwent hip arthroplasty with femoral shortening followed up for a minimum of 12 months. We found higher preoperative global lordosis (68.7 ± 9.7) and sacral slope (52.1 ± 8.8) angles, but the pelvic incidences (57.9 ± 10.1) were in the normal range. No statistically significant difference in any sagittal spinopelvic parameters between pre- and postoperative measurements was detected. GAP scores also did not change significantly (p = 0.231). Coronal plane parameters (Cobb angle, coronal pelvic tilt) were the only parameters in which a statistical change was observed (p = 0.02, p = 0.05, respectively). Conclusion: Lumbar lordosis and sacral slope values are outside standard ranges in patients with neglected dysplasia of the hip. The reconstruction of the distorted mechanics of the hip joint does not normalize sagittal pelvic and spine anatomy however improvements in coronal alignment were observed. Disease specific values of sagittal spinal alignment should be used in the treatment of lumbar degenerative problems in patients with neglected high hip dysplasia. Level of evidence: IV.