Radiographic parameters for evaluating hip development are altered by Salter osteotomy, and their prognostic value require further validation. A total of 63 patients who underwent open reduction and Salter osteotomy for unilateral hip dysplasia were evaluated with Severin classification 10.8 years later. The initial first-year postoperative acetabular index, c/b ratio, head–teardrop distance, and head coverage were compared with the final outcome of Severin classification. Greater c/b ratio was significantly associated with later Severin class III hip. Using receiver operating characteristics curve, a c/b ratio greater than 0.72 at 6 months and 1 year postoperatively can predict the possibility of a class III hip in 30 and 60% of patients, respectively.