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Scientific Articles   |    
Acetabular Retroversion in Developmental Dysplasia of the Hip
Masanori Fujii, MD1; Yasuharu Nakashima, MD, PhD1; Takuaki Yamamoto, MD, PhD1; Taro Mawatari, MD, PhD1; Goro Motomura, MD, PhD1; Akinobu Matsushita, MD1; Shuichi Matsuda, MD, PhD1; Seiya Jingushi, MD, PhD1; Yukihide Iwamoto, MD, PhD1
1 Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. E-mail address for M. Fujii: m-fujii@ortho.med.kyushu-u.ac.jp. E-mail address for Y. Nakashima: yasunaka@ortho.med.kyushu-u.ac.jp. E-mail address for T. Yamamoto: yamataku@ortho.med.kyushu-u.ac.jp. E-mail address for T. Mawatari: mawtaro@gmail.com. E-mail address for G. Motomura: goromoto@ortho.med.kyushu-u.ac.jp. E-mail address for A. Matsushita: a-matsu@ortho.med.kyushu-u.ac.jp. E-mail address for S. Matsuda: mazda@ortho.med.kyushu-u.ac.jp. E-mail address for S. Jingushi: Jingushi.orth@kyushuh.rofuku.go.jp. E-mail address for Y. Iwamoto: yiwamoto@ortho.med.kyushu-u.ac.jp
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Disclosure: The authors 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.

Investigation performed at the Department of Orthopaedic Surgery, Kyushu University, Fukuoka, Japan

Copyright ©2010 American Society for Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2010 Apr 01;92(4):895-903. doi: 10.2106/JBJS.I.00046
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Abstract

Background: 

Patients with developmental dysplasia of the hip are prone to the development of degenerative changes in the affected hip. The aim of this study was to evaluate the prevalence, morphological features, and clinical relevance of acetabular retroversion in these patients.

Methods: 

We investigated the version and morphological features of the acetabulum using pelvic radiographs and computed tomography images of ninety-six hips in fifty-nine patients with developmental dysplasia of the hip. A diagnosis of acetabular retroversion was based on the presence of a positive cross-over sign on the pelvic radiograph. Using computed tomography images, we determined the acetabular anteversion angle at various levels in the axial plane. The acetabular sector angle served as an indicator of acetabular coverage of the femoral head. We evaluated the association between acetabular version and the patient's age at the onset of pain. Fifty normal hips were examined as controls.

Results: 

We observed acetabular retroversion in 18% (seventeen) of the ninety-six hips in the patients with developmental dysplasia of the hip. The mean acetabular anteversion angle in the hips with acetabular retroversion was significantly smaller, at all levels, than that in the hips with acetabular anteversion; this tendency was more evident at proximal levels. There was significantly less posterior and posterosuperior coverage in the hips with acetabular retroversion than in those with acetabular anteversion, but superior acetabular coverage did not differ between the groups. Multivariate analysis showed that the onset of pain occurred at a significantly earlier age in patients with acetabular retroversion (27.9 years) than in those with acetabular anteversion (40.5 years), regardless of the severity of the dysplasia (p = 0.003).

Conclusions: 

In patients with developmental dysplasia of the hip, acetabular retroversion results from relatively deficient coverage by the posterior portion of the acetabulum. Developmental dysplasia with acetabular retroversion is associated with an earlier onset of pain than is developmental dysplasia with anteversion, suggesting a correlation between deficiency of the posterior acetabular wall and the earlier onset of pain.

Level of Evidence: 

Prognostic Level IV. See Instructions to Authors for a complete description of levels of evidence.

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    References

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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    Chen-Kun Liaw, MD, PhD
    Posted on February 11, 2011
    The Precision is Important for Acetabular Measurement
    Orthopaedic Doctor, Dept of Orthopaedics, Tao-Yuan General Hospital, Taoyuan, Taiwan, Dept of Orthopaedics, College of Medicine, National Taiwan University Hospital, Taipei City, Taiwan

    To the Editor:

    We read the recent article, "Acetabular Retroversion in Developmental Dysplasia of the Hip" by Fujii et al. (2010;92:895-903) and we had a few comments.

    First of all, we must always consider patient position when talking about the cross-over sign. In this study, the authors did not fully standardize the positions in the plain radiograph. Instead, the authors standardized the position by selecting the radiographs in which the symphysis pubis junction lined up with the center of the sacrococcygeal junction and the distance was between 25 to 40mm for males and 40 to 55mm for females. We calculated how much these different situations will affect the acetabular version as follows:

    According to our previous study (1), radiographic standardize acetabular version (Liaw's version)
    =arc sin((-h × sinφ × cosθ+v × cosφ × cosθ+ sinθ × (ssd2-h2- v2)0.5)/ssd)

    h means the horizontal position of the center of the sacral-coccygeal junction in relation to the symphysis pubis junction. In this case, h is 0.

    v means the vertical position of the center of sacral-coccygeal junction in relation to the symphysis pubis junction. In this case, v ranges from 25 to 40mm for males and 40 to 55mm for females.

    ssd is the anatomical distance between the symphysis pubis junction and the center of the sacro-coccygeal junction. As the paper assumed, we set it at 143mm (1).

    According to this formula, we calculated acetabular version differences under different positions by assuming the same Liaw's version. This calculation is equal to calculating the Liaw's version difference by assuming the same acetabular version and then calculating the Liaw's version difference with different conditions. If the inclination was 30 degrees, the Liaw's version's difference was 5.3 degrees for males and 5.4 degrees for females. If the inclination was 60 degrees, the Liaw's version's difference was 3.0 degrees for both genders (Table 1).

    Table 1: Liaw's version differences under different situations.
    Acetabular
    version
    InclinationhvLiaw's
    version
    Difference
    0300258.7085.311
    03004014.019
    03004014.0195.437
    03005519.456
    0600255.0153.025
    0600408.040
    0600408.0403.048
    06005511.087

    Clinicians might postulate that 3 to 5 degrees difference is small. However, if the anteversion or retroversion angle is smaller than this difference, this minor change will significantly interfere with the results.

    Secondly, the definition of the cross-over sign should be clarified. In the original paper by Reynolds et al., the cross-over sign is defined as the anterior edge of acetabulum lateral to the posterior edge (2). An example of a radiograph is presented in figure 1. The edges were marked with a red line. The cross-over sign was evident because the two lines crossed. If we look at the position of the two lines, the posterior edge line is lateral to the anterior edge line. How did the authors deal with this situation? Will they judge these situations as cross-over positive or negative? This important issue was not addressed in the report by the authors and warrants further study.


    Fig 1. Figure 1. An exemplary antero-posterior plain radiograph of left hip taken in Taoyuan, Taiwan in 2010. We marked the anterior and posterior edges of the acetabulum with red lines. The two lines crossed, and the posterior edge line was lateral to the anterior edge line.

    References

    1. Liaw CK, Yang RS, Hou SM, Wu TY, Fuh CS. A simple mathematical standardized measurement of acetabulum anteversion after total hip arthroplasty. Computat Math Meth Med. 2010;9:105-19.

    2. Reynolds D, Lucas J, Klaue K. Retroversion of the acetabulum. A cause of hip pain. J Bone Joint Surg Br. 1999;81:281-8.

    Masanori Fujii, MD
    Posted on February 11, 2011
    Dr. Fujii and colleagues respond to Drs. Liaw and Wu
    Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University , Japan

    We appreciate Dr. Liaw's interest in our paper. Basically, we agree with the comment that the position of the pelvis significantly affects the presence of the cross-over sign on an anteroposterior pelvic radiograph. Thus, it is important to confirm that the radiograph was taken with the patients in an appropriate pelvic position. In this study, we utilized the previously reported criterion of the normal pelvic tilt based on its validity. We believe our patient selection was practically appropriate. It would be one of the limitations to these studies that the radiograph was not taken with the entire patient in the exactly equivalent pelvic position. The formula of Dr. Liaw is a useful way to predict the acetabular version in artificial hip joint. However, we have a concern of its application for the dysplastic hip. The morphological character of the dysplastic hip such as shallow acetabulum, and the irregular profile of the natural acetabular rim jeopardize the assumption that the acetabular geometry is hemispherical. For the second pointing out, we mentioned the definition of the positive cross-over sign as the anterior aspect of the acetabular rim being more lateral than the posterior aspect in the proximal portion of the acetabulum in this study. The proximal portion of the acetabulum means the portion proximal to the point that the lines of anterior and posterior acetabular rim cross.

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