To The Editor:

In the paper "Hip Rotational Acetabular Osteotomy for Advanced Osteoarthritis Secondary to Dysplasia of the Hip" (1), Yasunaga et al. presented their experience on acetabular osteotomy to treat advanced osteoarthritis secondary to hip dysplasia in the young adults. The authors measured many radiological parameters, including the center-edge angle, the mean acetabular roof angle, the mean head lateralization index, and the mean minimum width of the joint space.

However, they did not report the anteversion values of these acetabulae pre or post operatively. The report of Parvizi et al.(2) states that range of motion of the hip is influenced by the anteversion of acetabulum and it will be expected to change after pelvic osteotomy. In addition, suitable correction is important because retroversion of the hip (positive cross- over sign) may predispose to osteoarthritis.(3,4,5)

Since this article(1) did not provide the radiographs for study, we reviewed the radiographs of patients presented in the article by Ninomiya and Tagawa(6) that discussed the same osteotomy technique. We determined the presence or absence of the cross-over sign before and after operation, and we measured the radiographic anteversion of the hips using our previous published method(7). Fig.1A(below) shows that there is negative cross-over sign (anteverted hips) preoperatively, and figure 1B shows a positive cross-over sign (neutral or retroverted hips) postoperatively in one of the patients presented in that article(6). Fig.2(below) uses our method(7) to measure the radiographic anteversion of the acetabulum in one of the hips from the same patient (6). In this example, the anteversion is 17 degrees.

In Table 1 (below) we show the presence or absence of the cross-over sign and magnitude of radiographic anteversion that we measured on the 4 patients (5 hips) presented in the paper by Ninomiya and Tagawa(6). The cross-over sign was negative in four of five hips before operation, while after operation the cross-over sign was positive in all hips which indicates reduced anteversion or retroversion. The mean radiographic anteversion of the acetabulum before osteotomy was 17.4 degrees (range: 10 to 25 degrees. In contrast,the post osteotomy mean anteversion was 2 degrees(range: -10 to 5 degrees)(paired t-test, p=0.001). Since correction into anteversion may play an important role in preventing osteoarthritis progression, we would be grateful to know the pre and post operative anteversion values of the patients reported in the present study (1).

Fig. 1-A

Fig. 1-B

Fig. 2

Table 1

The authors of this did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.

References:

1. Yuji Yasunaga, Mitsuo Ochi, Hiroshi Terayama, Ryuji Tanaka, Takuma Yamasaki and Yoshimasa Ishii. Hip rotational acetabular osteotomy for advanced osteoarthritis secondary to dysplasia of the hip. J Bone Joint Surg Am. 2006;88:1915-1919.

2. Parvizi J., Campfield A., Clohisy J. C., Rothman R. H., Mont, MA. Management of arthritis of the hip in the young adult. J Bone Joint Surg Br. 2006 88-B: 1279-1285

3. Ganz R, Parvizi J, Beck M, et al. Femoroacetabular impingement: A cause for osteoarthritis of the hip. Clin Orthop. 2003;417:112-20.

4. Parvizi J, Ganz R. Femoroacetabular impingement. Sem Arthroplasty. 2005;16:33-37.

5. Siebenrock KA, Schoengiger R, Ganz R. Anterior femoroacetabular impingement due to acetabular retroversion: treatment with periacetabular osteotomy. J Bone Joint Surg Am. 2003;85-A:278-86.

6. S Ninomiya, H Tagawa. Rotational acetabular osteotomy for the dysplastic hip. J Bone Joint Surg Am. 1984;66:430-436.

7. Liaw CK, Hou SM, Yang RS, et al. A new tool for measuring cup orientation in total hip arthroplasties from plain radiographs. Clin Orthop. 2006;451:134-139.