Acetabular dysplasia may present as previously undiagnosed or as a sequel to treated DDH in a young adult, with a natural history of subsequent development of early osteoarthritis.

Patients with acetabular dysplasia and a normal neck shaft angle, no significant leg length inequality and who demonstrate congruency at arthrogram are considered suitable for realignment pelvic osteotomy.

We report the results of 15 young adults who underwent a modified Tonnis triple osteotomy with a mean 21-month follow up. The modification was the ischial osteotomy being performed through a groin incision.

The only common complication was the requirement of catheterisation post-operatively (60%). There were no infections. There was 1 delayed union but no non-unions. One patient developed a deep vein thrombosis. All patients reported an improvement in their symptoms and level of activity, with a mean post-operative Harris hip score of 92. All showed an improved centre-edge angle of 28° (mean increase of 18°) and acetabular angle 37° (mean decrease of 13°).

The early results of this procedure show this to be a safe and useful option to delay the natural history of early osteoarthritis in the young adult.