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Validity of the alpha angle measurements on plain radiographs in the evaluation of cam-type femoroacetabular impingement in patients with slipped capital femoral epiphysis

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Abstract

Objective

The purpose of the study was to investigate the correlation of two different alpha angle (a-angle) measurements (“anatomical method and “three-point method”) with the anterior offset ratio (AOR), femoral head ratio (FHR), and lateral femoral head ratio (LFHR) in patients with slipped capital femoral epiphysis (SCFE).

Materials and methods

We included 39 hips of 26 patients. The a-angles were measured on the frog-leg lateral view (Lat) and anteroposterior (Ap) view, FHR was measured on the Ap view, and LFHR and AOR were measured on the Lat view. A t test was performed to analyze the means of the alpha angles measured using the three-point method and the anatomical method, and also, a correlation was conducted to assess the association of the a-angles among the FHR, LFHR, and AOR.

Results

The mean a-angles in the Ap plane in the three-point method and anatomical method were 76° ± 15° and 64° ± 10° respectively (p < 0.001). The mean a-angles in the Lat plane in the three-point method and anatomical method were 67° ± 13° and 56° ± 11° respectively (p < 0.001). The AOR showed a significant correlation only with the anatomical method a-angle values in the Lat plane (p = 0.026). The a-angles in the three-point method in the Lat plane did not show any significant correlation with the AOR, FHR, and LFHR. Both the FHR and LFHR values correlated significantly with the Ap plane a-angles in the three-point method and anatomical method. However, none of these correlations was strong.

Conclusions

The a-angle measurement methods described in patients without femoral head–neck axis disruption may not be valid in patients with a disorder such as SCFE.

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Funding

No funding support was received for this study.

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Authors and Affiliations

  1. Faculty of Medicine, Erzincan University, Basbaglar mahallesi, 24030, Erzincan, Turkey

    Hanifi Ucpunar & Yalkin Camurcu

  2. Baltalimani Bone and Joint Diseases Education and Research Hospital, Rumelihisari caddesi No: 62, 34470, Istanbul, Turkey

    Muhammed Mert & Abdul Fettah Buyuk

  3. Kayseri City Hospital, Şeker Mah. Molu Cad. Kocasinan Mah. 38080 / Kayseri, Turkey

    Adem Cobden

  4. Medical Park Bahcelievler Hospital, Bahçelievler Mahallesi, Kültür Sok., E5 Yolu No:1, 34180, Bahçelievler/İstanbul, Turkey

    Hakan Sofu

Authors
  1. Hanifi Ucpunar
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  2. Muhammed Mert
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  4. Abdul Fettah Buyuk
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  6. Hakan Sofu
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Correspondence to Hanifi Ucpunar.

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Conflicts of interest

None of the authors has any conflicts of interest and nothing to disclose.

Informed consent

Informed consent was not obtained from the patients included in this study given the retrospective design of the study.

Ethical review committee statement

This study has been approved by the ethical review committee and institutional review board of Baltalimani Bone and Joint Diseases Education and Research Hospital.

Location where the work was performed

This study was conducted in Baltalimani Bone and Joint Diseases Education and Research Hospital (also the previous workplace of all authors) where all the patients underwent surgery.

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Ucpunar, H., Mert, M., Camurcu, Y. et al. Validity of the alpha angle measurements on plain radiographs in the evaluation of cam-type femoroacetabular impingement in patients with slipped capital femoral epiphysis. Skeletal Radiol 48, 1787–1794 (2019). https://doi.org/10.1007/s00256-019-03224-x

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  • DOI: https://doi.org/10.1007/s00256-019-03224-x

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