Spontaneous fusion of 'os acetabuli' after triple pelvic osteotomy.

In acetabular dysplasia, an overloading of the acetabular rim can cause a stress fracture, creating an 'os acetabuli', or a lesion of the acetabular labrum. At puberty, the os acetabuli seems to be the epiphysis of the os pubis. We present the case of a 14-year-old girl with acetabular dysplasia and spontaneous fusion of an 'os acetabuli' after biomechanical correction by triple pelvic osteotomy. Our report supports the correctness of the biomechanical principle: reorientation of the acetabulum results in a better coverage of the femoral head, reduces the stress at the acetabular rim, shifts the os acetabuli out of the stress region, and may allow union of the bony fragment with the acetabulum.