Skip to main content
Log in

Comparison of MRI Alpha Angle Measurement Planes in Femoroacetabular Impingement

  • Symposium: Femoroacetabular Impingement: Current Status of Diagnosis and Treatment
  • Published:
Clinical Orthopaedics and Related Research

Abstract

Insufficient femoral head-neck offset is common in femoroacetabular impingement (FAI) and reflected by the alpha angle, a validated measurement for quantifying this anatomic deformity in patients with FAI. We compared the alpha angle determined on magnetic resonance imaging (MRI) oblique axial plane images with the maximal alpha angle value obtained using radial images. The MRIs of 41 subjects with clinically suspected FAI were reviewed and alpha angle measurements were performed on both oblique axial plane images parallel to the long axis of the femoral neck and radial images obtained using the center of the femoral neck as the axis of rotation. The mean oblique axial plane and mean maximal radial alpha angle values were 53.4° and 70.5°, respectively. In 54% of subjects, the alpha angle was less than 55° on the conventional oblique axial plane image but 55° or greater on the radial plane images. Radial images yielded higher alpha angle values than oblique axial images. Patients with clinically suspected FAI may have a substantial contour abnormality that can be underestimated or missed if only oblique axial plane images are reviewed. Radial plane imaging should be considered in the MRI investigation of FAI.

Level of Evidence: Level III, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Subscribe and save

Springer+ Basic
EUR 32.99 /Month
  • Get 10 units per month
  • Download Article/Chapter or Ebook
  • 1 Unit = 1 Article or 1 Chapter
  • Cancel anytime
Subscribe now

Buy Now

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Fig. 1A–C
Fig. 2
Fig. 3A–B

Similar content being viewed by others

References

  1. Beaulé P, Zaragoza E, Motamedi E, Copelan N, Dorey F. Three-dimensional computed tomography of the hip in the assessment of femoroacetabular impingement. J Orthop Res. 2005;23:1286–1292.

    PubMed  Google Scholar 

  2. Beck M, Kalhor M, Leunig M, Ganz R. Hip morphology influences the pattern of damage to the acetabular cartilage. J Bone Joint Surg Br. 2005;87:1012–1018.

    Article  PubMed  CAS  Google Scholar 

  3. Ganz R, Leunig M, Leunig-Ganz K, Harris WH. The etiology of osteoarthritis of the hip: an integrated mechanical concept. Clin Orthop Relat Res. 2008;466:264–272.

    Article  PubMed  Google Scholar 

  4. Ganz R, Parvizi J, Beck M, Leunig M, Nötzli H, Siebenrock KA. Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop Relat Res. 2003;417:112–120.

    PubMed  Google Scholar 

  5. Ito K, Minka KA, Leunig M, Werlen S, Ganz R. Femoroacetabular impingement and the cam-effect: a MRI-based quantitative anatomical study of the femoral head-neck offset. J Bone Joint Surg Br. 2001;83:171–176.

    Article  PubMed  CAS  Google Scholar 

  6. James SLJ, Ali K, Malara F, Young D, O’Donnell J, Connell DA. MRI findings of femoroacetabular impingement. AJR Am J Roentgenol. 2006;187:1412–1419.

    Article  PubMed  Google Scholar 

  7. Kassarjian A, Yoon LS, Belzile E, Connolly SA, Millis MB, Palmer WE. Triad of MR arthrographic findings in patients with cam-type femoroacetabular impingement. Radiology. 2005;236:588–592.

    Article  PubMed  Google Scholar 

  8. Meyer DC, Beck M, Ellis T, Ganz R, Leunig M. Comparison of six radiographic projections to assess femoral head/neck asphericity. Clin Orthop Relat Res. 2006;445:181–185.

    PubMed  Google Scholar 

  9. Nötzli HP, Wyss TF, Stoecklin CH, Schmid MR, Treiber K, Hodler J. The contour of the femoral head-neck junction as a predictor for the risk of anterior impingement. J Bone Joint Surg Br. 2002;84:556–560.

    Article  PubMed  Google Scholar 

  10. Pfirrmann CWA, Mengiardi B, Dora C, Kalberer F, Zanetti M, Hodler J. Cam and pincer Femoroacetabular impingement: characteristic MR arthrographic findings in 50 patients. Radiology. 2006;240:778–785.

    Article  PubMed  Google Scholar 

  11. Siebenrock KA, Wahab KHA, Werlen S, Kalhor M, Leunig M, Ganz R. Abnormal extension of the femoral head epiphysis as a cause of cam impingement. Clin Orthop Relat Res. 2004;418:54–60.

    Article  PubMed  Google Scholar 

  12. Tannast M, Sienbenrock KA, Anderson SE. Femoroacetabular impingement: radiographic diagnosis—what the radiologist should know. AJR Am J Roentgenol. 2007;188:1540–1552.

    Article  PubMed  Google Scholar 

Download references

Acknowledgments

We thank Anna Fazekas and Simon Dagenais for assistance in study design and statistical analysis and Natasha La Russa for postprocessing reformations of the MRI studies.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Kawan S. Rakhra MD, FRCPC.

Additional information

Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.

Each author certifies that his or her institution has approved or waived approval for the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research.

About this article

Cite this article

Rakhra, K.S., Sheikh, A.M., Allen, D. et al. Comparison of MRI Alpha Angle Measurement Planes in Femoroacetabular Impingement. Clin Orthop Relat Res 467, 660–665 (2009). https://doi.org/10.1007/s11999-008-0627-3

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s11999-008-0627-3

Keywords

Navigation