title: Do normal radiographs exclude asphericity of the femoral head-neck junction?
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.
authors.affiliation: Department of Orthopaedic Surgery, Inselspital, University of Berne, Freiburgstrasse, 3010, Bern, Switzerland. Marcel.Dudda@rub.de
authors.forename: Marcel
authors.initials: M
authors.lastname: Dudda
authors.forename: Christoph
authors.initials: C
authors.lastname: Albers
authors.forename: Tallal Charles
authors.initials: TC
authors.lastname: Mamisch
authors.forename: Stefan
authors.initials: S
authors.lastname: Werlen
authors.forename: Martin
authors.initials: M
authors.lastname: Beck
mesh_terms: D000293:Adolescent; D000328:Adult; D001175:Arthrography; D005270:Femur Head / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005272:Femur Neck / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D007592:Joint Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D011237:Predictive Value of Tests; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D055815:Young Adult