Spinopelvic assessment in preoperative planning of total hip arthroplasty: a comparative cohort analysis.

Objective: This study aimed to evaluate the utility of preoperative spinopelvic analysis in reducing dislocation risk and to assess changes in spinopelvic mobility following total hip arthroplasty (THA). Methods: This cohort was assessed between 2018 and 2021, including 123 patients (123 hips) who underwent THA via the posterolateral approach. Group 1 (63 hips, 61 patients) underwent spinopelvic analysis with standing and sitting radiographs preoperatively and at 1- and 2-year follow-up, while Group 2 (62 hips, 62 patients) did not. Patients with Crowe type III-IV dysplasia, neurological or cognitive disorders, or acute trauma were excluded. Sacral slope (SS), spinopelvic tilt (sPT), and pelvic femoral angle were assessed. Intergroup comparisons were performed to evaluate the dislocation rates and changes in spinopelvic mobility. Results: One dislocation occurred in Group 1 and 3 in Group 2. In Group 1, significant changes were observed in sitting SS (preoperative to year 1: P < .001; year 2: P=.003) and sitting sPT (year 1: P=.004; year 2: P=.043), while standing measurements remained stable (SS: P=.762-.470; sPT: P=.683-.600). Mean sitting hip flexion also increased significantly (P < .001). Among 26 patients with hypermobility, 18 demonstrated normalization at 1 year, and 2 additional patients normalized at 2 years. In 1 patient with hypomobility, adjustment of acetabular anteversion based on spinopelvic findings successfully prevented dislocation. Conclusion: Preoperative spinopelvic analysis enabled the identification of mobility abnormalities and allowed for targeted surgical adjustments that may reduce dislocation risk. Notably, dislocations could potentially have been avoided with prior spinopelvic evaluation, underscoring its clinical relevance in preoperative planning. Postoperatively, SS increased exclusively in the sitting position, while remaining unchanged in standing position, reinforcing the necessity of seated imaging for comprehensive assessment. Level of Evidence: Level II, Cohort Study.