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Comparative Study
. 2009 Mar;467(3):651-9.
doi: 10.1007/s11999-008-0617-5. Epub 2008 Nov 20.

Do normal radiographs exclude asphericity of the femoral head-neck junction?

Marcel Dudda  1 , Christoph Albers, Tallal Charles Mamisch, Stefan Werlen, Martin Beck
Affiliations
Comparative Study

Do normal radiographs exclude asphericity of the femoral head-neck junction?

Marcel Dudda et al. Clin Orthop Relat Res. 2009 Mar.

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.

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Figures

Fig. 1A–B
Fig. 1A–B
(A) Anteroposterior pelvis view of a patient without radiographic signs of femoroacetabular impingement (Group I). (B) Lateral crosstable view of a patient without radiographic signs of femoroacetabular impingement (Group I).
Fig. 2A–B
Fig. 2A–B
(A) Anteroposterior pelvis view of a patient with radiographic signs of femoroacetabular impingement in both planes (Group IV). (B) Lateral crosstable view of a patient with radiographic signs of femoroacetabular impingement in both planes (Group IV).
Fig. 3
Fig. 3
Construction of the alpha angle as described by Nötzli et al. [18].
Fig. 4
Fig. 4
Magnetic resonance arthrogram slice of radial slices showing the measurement of the height of asphericity at an alpha angle of 43°.
Fig. 5
Fig. 5
Schematic of the proximal femur showing the clockwise rotation of the MRI slices, in which measurements were taken.
Fig. 6A–H
Fig. 6A–H
(A) Example of a MRA radial slice at 3 o’clock position (posterior) at the femoral neck axis. (B) Example of a MRA radial slice at 2 o’clock position at the femoral neck axis. (C) Example of a MRA radial slice at 1 o’clock position at the femoral neck axis. (D) Example of a MRA radial slice at 12 o’clock position (superior) at the femoral neck axis. (E) Example of a MRA radial slice at 11 o’clock position at the femoral neck axis. (F) Example of a MRA radial slice at 10 o’clock position at the femoral neck axis. (G) Example of a MRA radial slice at 9 o’clock position (anterior) at the femoral neck axis. (H) Magnetic resonance arthrogram radial slice localizer.
Fig. 7
Fig. 7
Diagram showing the alpha angles in Group I that included hips with spherical contours on both the anteroposterior pelvis and lateral crosstable views. No signs of asphericity.
Fig. 8
Fig. 8
Diagram showing the height of the asphericity in Group I that included hips with spherical contours on both the anteroposterior pelvis and lateral crosstable views. No signs of asphericity.
Fig. 9
Fig. 9
Diagram showing the alpha angles in Group II that included hips with asphericity on the lateral crosstable view only.
Fig. 10
Fig. 10
Diagram showing the height of asphericity in Group II that included hips with asphericity on the lateral crosstable view only.
Fig. 11
Fig. 11
Diagram showing the alpha angles in Group III that had asphericity of the hip on the anteroposterior pelvis (eg, pistol grip deformity) and normal contour in the lateral crosstable view.
Fig. 12
Fig. 12
Diagram showing the height of asphericity in Group III that had asphericity of the hip on the anteroposterior pelvis (eg, pistol grip deformity) and normal contour in the lateral crosstable view.
Fig. 13
Fig. 13
Diagram showing alpha angles in Group IV that included hips with aspheric head-neck junction on both views.
Fig. 14
Fig. 14
Diagram showing the height of asphericity in Group IV that included hips with aspheric head-neck junction on both views.
See this image and copyright information in PMC

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