International Orthopaedics

, Volume 40, Issue 4, pp 687–695 | Cite as

Modified head-neck offset for diagnosing anterior femoro-acetabular impingement

  • Aloїs Espié
  • Fanny Elia
  • Jérôme Murgier
  • Philippe Chiron
  • Benoit Chaput
Original Paper



The head-neck offset described by Eijer et al. (eHNO), which is used to diagnose anterior femoro-acetabular impingement (FAI), can be difficult to measure. The aim of this study was to verify if a modified head-neck offset (mHNO) provides more accurate and reproducible values than those of the eHNO.


The eHNO, mHNO, cephalic radius and alpha angle were measured on frog-leg radiographs of a group of patients with FAI and a control group (T); three independent reviewers measured the 50 hips in each group twice. The comparison of the two HNOs focused on reproducibility (intraclass correlation coefficient), validity (correlation with alpha angle), practical utility (difference between means in the FAI and control groups) and accuracy of the diagnostic thresholds.


The mHNO had better reproducibility (p < 0.05) within and between observers in all study subjects than that of the eHNO (0.938 and 0.979 vs 0.881 and 0.904). The correlation with the alpha angle was also better (p < 0.05) for the mHNO than that for the eHNO. The diagnostic performances of the mHNO and mAOR thresholds were higher than those of the eHNO, eAOR and alpha angle.


The new HNO is easier to measure, more reproducible and more accurate. A modified HNO <5 mm and a modified AOR <0.100 on the frog-leg view argued in favour of a pathological cam-type head-neck junction.


Femoro-acetabular impingement Cam effect Alpha angle Head-neck offset Frog-leg view 


Conflict of interest

P. Chiron is a consultant for Zimmer, Sanofi and Smith & Nephew, and has received royalties from Zimmer and Integra. The other authors declare that they have no conflicts of interest related or unrelated to this article.

Supplementary material

264_2015_2834_Fig5_ESM.gif (91 kb)

Head-neck offset (red arrow) as Eijer et al. [1]. Line A neck axis, line B parallel to A and tangent to the cortex of the femoral neck, line C parallel to A and tangent to the head. (GIF 91 kb)

264_2015_2834_MOESM1_ESM.tif (800 kb)
High Resolution (TIFF 799 kb)
264_2015_2834_Fig6_ESM.gif (109 kb)

Example of a radiograph with an Eijer’s offset difficult to measure: Eijer’s HNO = 8.6 mm; modified HNO = 0.8 mm.h (GIF 108 kb)

264_2015_2834_MOESM2_ESM.tif (1.6 mb)
High Resolution (TIFF 1592 kb)


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Copyright information

© SICOT aisbl 2015

Authors and Affiliations

  • Aloїs Espié
    • 1
  • Fanny Elia
    • 2
  • Jérôme Murgier
    • 2
  • Philippe Chiron
    • 2
  • Benoit Chaput
    • 2
  1. 1.Clinique Saint Jean du LanguedocToulouseFrance
  2. 2.Service de Chirurgie Orthopédique, Secteur A, 5ème étage, Hôpital Pierre-Paul RiquetCHU Toulouse PurpanToulouse CEDEX 9France

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