The periacetabular osteotomies are effective but technically demanding surgical procedures in the treatment of adult dysplastic hips. We developed a modified technique which combines the two most popular surgeries: the rotational acetabular osteotomy (RAO), and the Bernese osteotomy. Transtrochanteric approach was used in our new spherical osteotomy and provided a good surgical exposure for redirecting the acetabulum with minimal complications. This article describes the surgical procedures in detail and reports the preliminary results in the first 32 hips. As the experiences are encouraging in terms of technical ease and reproducibility, the authors feel that this new osteotomy with transtrochanteric exposure is an ideal choice of surgery in treating residual hip dysplasia in the adult. Key words: osteotomy, periacetabular, hip dysplasia, adult.