Symposium: Femoroacetabular Impingement: Current Status of Diagnosis and Treatment

Clinical Orthopaedics and Related Research

, Volume 467, Issue 3, pp 651-659

Do Normal Radiographs Exclude Asphericity of the Femoral Head-Neck Junction?

  • Marcel DuddaAffiliated withDepartment of Orthopaedic Surgery, Inselspital, University of Berne Email author 
  • , Christoph AlbersAffiliated withDepartment of Orthopaedic Surgery, Inselspital, University of Berne
  • , Tallal Charles MamischAffiliated withDepartment of Orthopaedic Surgery, Inselspital, University of Berne
  • , Stefan WerlenAffiliated withDepartment of Radiology, Hospital Sonnenhof
  • , Martin BeckAffiliated withDepartment of Orthopaedic Surgery, Inselspital, University of Berne

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Abstract

Asphericity of the femoral head-neck junction is one cause for femoroacetabular impingement of the hip. However, the asphericity often is underestimated on conventional radiographs. This study compares the presence of asphericity on conventional radiographs with its appearance on radial slices of magnetic resonance arthrography (MRA). We retrospectively reviewed 58 selected hips in 148 patients who underwent a surgical dislocation of the hip. To assess the circumference of the proximal femur, alpha angle and height of asphericity were measured in 14 positions using radial slices of MRA. The hips were assigned to one of four groups depending on the appearance of the head-neck junction on anteroposterior pelvic and lateral crosstable radiographs. Group I (n = 19) was circular on both planes, Group II (n = 19) was aspheric on the crosstable view, Group III (n = 4) was aspheric on the anteroposterior view, and Group IV (n = 13) was aspheric on both views. In all four groups, the highest alpha angle was found in the anterosuperior area of the head-neck junction. Even when conventional radiographs appeared normal, an increased alpha angle was present anterosuperiorly. Without the use of radial slices in MRA, the asphericity would be underestimated in these patients.

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