Periacetabular osteotomy for hip dysplasia treatment through a mini-invasive technique. Our results at mid-term in 131 cases L. Ramírez-Núñez; J. Payo-Ollero; M. Comas; C. Cárdenas; V. Bellotti; E. Astarita; G. Chacón-Cascio; M. Ribas;