Traumatic disruption of the acetabular triradiate cartilage is an infrequent injury. When it occurs in young children, it may lead to premature physeal closure, even with little or no displacement of the innominate bones at the time of injury. Premature physeal closure results in a physeal osseous bar and progressive thickening of the wall of the acetabulum. This causes the acetabular cavity to become more shallow, resulting in gradual extrusion of the femoral head, subluxation, and eventually, hemipelvic hypoplasia and dysplasia of the hip1,2,10,13. Acetabular reconstruction is sometimes used to correct these abnormalities. Variable irregularities of growth at the proximal end of the femur, such as flattening of the medial side of the femoral capital epiphysis and coxa valga, also may occur.
In some patients, the physeal osseous bar may be small and located in a position that is amenable to excision. We are reporting the case of a patient who had what we believe to be the first successful excision of such a bar. The patient was followed for twelve years and four months postoperatively.
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
†Mayo Clinic, 200 First Street, S.W., Rochester, Minnesota, 55905. Please address requests for reprints to Dr. Peterson.
‡6565 South Yale, Suite 1200, Tulsa, Oklahoma 74136.
The growth and development of the normal triradiate cartilage have been well documented2,9. Research on animals3-5,7,8,12 and case reports1,2,6,8,10,11,13,14 have documented that premature closure of the triradiate cartilage following trauma or infection has deleterious effects on the growth of the acetabulum, resulting in a shallow acetabulum, lateral extrusion of the femoral head, subluxation, and eventually dysplasia. Several types of corrective pelvic osteotomies have been performed in an attempt to correct these abnormalities1,2,11,13.
In 1982, Bucholz et al. stated: "Theoretically, if the osseous bridge were removed surgically, growth would resume and the normal shape of the acetabulum might be preserved. However, the rapid development of the osseous bridge and progression to closure of the triradiate cartilage certainly suggest that resection of the bridge and implantation of fat . . . may not have much success." Indeed, in 1980, Dias et al. reported a failure after excision of a triradiate osseous bridge that was filled with fat.
In the case reported here, after excision of the osseous bridge (in September 1982), the physis remained open and endochondral ossification proceeded normally, as evidenced by the increase in distance between the metal markers. Initially after the excision, the depth of the acetabulum and the width of its inner wall remained equal to those of the contralateral, normal acetabulum. After further growth and some time in adolescence, the acetabular triradiate cartilage on the right apparently closed earlier than that on the left, resulting in a very slight increase in the thickness of the acetabular wall and lateral displacement of the femoral head. This commonly occurs after excisions of the bars at other sites as well. Nevertheless, the result in our patient is superior to that reported for a patient who had a similar lesion but no treatment1. That patient had more severe thickening of the acetabular wall and more lateral displacement of the femoral head.
Small physeal bars of the triradiate cartilage may be amenable to excision. Early recognition and treatment before premature closure of the entire physis and before permanent osseous deformity are essential for a good outcome.