Temporal trends in patients undergoing transposition osteotomy of the acetabulum at a single center in Japan: A 25-year retrospective cohort study

ABSTRACT Purpose Although the clinical presentation of hip dysplasia has changed over recent decades, long-term temporal trends in patients undergoing periacetabular osteotomy remain poorly characterized. This study aimed to determine temporal trends among patients undergoing transposition osteotomy of the acetabulum (TOA) at a single center in Japan. Methods We retrospectively reviewed patients with symptomatic hip dysplasia who underwent TOA from 1998 to 2023. Demographic variables and preoperative radiographic parameters, including the Tönnis osteoarthritis grade and lateral center-edge angle, were evaluated. Temporal trends were assessed using the Cochran–Armitage trend test for categorical variables and the Mann–Kendall trend test for continuous variables. Results Overall, 715 patients (958 hips) were included. No significant temporal trends were observed in age or sex distribution, whereas body mass index showed a modest increasing trend ( p = 0.016). The proportion of hips with a history of treatment for congenital hip dislocation decreased over time ( p < 0.001). Radiographically, the proportion of hips with Tönnis grade 0 increased, whereas the proportions with grades 1 and 2 decreased over the study period ( p < 0.001). The lateral center-edge angle showed an increasing trend, indicating a reduction in severe dysplasia and an increase in mild and borderline dysplasia ( p < 0.001). Conclusions Over 25 years, patients undergoing TOA at our institution shifted toward earlier-stage osteoarthritis and milder hip dysplasia. These trends may reflect changes in disease presentation, patient selection, and institutional practice. Recognizing these trends is essential for interpreting historical outcomes and refining contemporary patient selection and surgical strategy.