Introduction To treat neglected developmental dysplasia of the hip (DDH), we performed Salter innominate osteotomy with a modification of transiliac lengthening. We asked whether this modified technique caused posterior coverage problems and triradiate cartilage injury. Methods We retrospectively reviewed 45 patients with unilateral DDH treated by open reduction and femoral shortening and modified Salter innominate osteotomy. The age at operation was 38.44 ± 19.79 months (mean ± standard deviation). Minimum follow-up was 24 months (mean ± standard deviation 49.84 ± 27.73 months; range 24–112 months). We measured the tilt of the iliac bone (difference of preoperative and postoperative acetabular index values). We divided the hips into two groups. There were 29 hips in Group 1 (deviation amount <20°) and 16 hips in Group 2 (deviation amount ≥20°). At the latest follow-up, frontal and axial plane computed tomographic analyses were performed. We measured medial wall thickness, teardrop width, and hemipelvis heights to evaluate triradiate cartilage intactness indirectly. Posterior center edge angle, which reflects posterior coverage of the hip, was also measured. Results We found no differences between groups regarding all measured parameters. Conclusions Modified Salter osteotomy with transiliac lengthening can be performed safely in the treatment of neglected DDH.