Traumatic premature fusion of the triradiate cartilage is a rare complication of fractures of the pelvis in children. Only five cases were reported, leading eventually to subluxation of the hip. A case of premature closure of the triradiate cartilage where the injury occurred at the age of four years is reported. Severe hip subluxation with marked shallow acetabulum and widening of its medial wall was noted at the age of 15 years. Intrapelvic epiphysiodesis of the triradiate cartilage, without disturbing the hip joint, was performed in young rabbits, leading to thickening of the acetabular medial wall and subluxation of the hip. Fusion of the triradiate cartilage in young age leaves the growth plate inside the acetabulum intact, it continues to grow, displacing the acetabulum laterally. As the acetabulum becomes more shallow, the hip progresses to subluxation.