title: Pelvic morphology in ischiofemoral impingement.
abstract: OBJECTIVE
  To assess MRI measures to quantify pelvic morphology that may predispose to ischiofemoral impingement (IFI). We hypothesized that patients with IFI have a wider interischial distance and an increased femoral neck angle compared with normal controls.
  
  
  METHODS
  The study was IRB-approved and complied with HIPAA guidelines. IFI was diagnosed based on clinical findings (hip or buttock pain) and ipsilateral edema of the quadratus femoris muscle on MRI. Control subjects did not report isolated hip/buttock pain and underwent MRI for surveillance of neoplasms or to exclude pelvic fractures. Two MSK radiologists measured the ischiofemoral (IF) and quadratus femoris (QF) distance, the ischial angle as a measure of inter-ischial distance, and the femoral neck angle. The quadratus femoris muscle was evaluated for edema. Groups were compared using ANOVA. Multivariate standard least-squares regression modeling was used to control for age and gender.
  
  
  RESULTS
  The study group comprised 84 patients with IFI (53 ± 16 years, 73 female, 11 male) and 51 controls (52 ± 16 years, 33 female, 18 male). Thirteen out of 84 patients (15%) had bilateral IFI. Patients with IFI had decreased IF and QF distance (p < 0.0001), increased ischial angle (p = 0.004), and increased femoral neck angle (p = 0.02) compared with controls, independent of age and gender.
  
  
  CONCLUSIONS
  Patients with IFI have increased ischial and femoral neck angles compared with controls. These anatomical variations in pelvic morphology may predispose to IFI. MRI is a useful method of not only assessing the osseous and soft-tissue abnormalities associated with IFI, but also of quantifying anatomical variations in pelvic morphology that can predispose to IFI.
authors.affiliation: Department of Radiology, Musculoskeletal Imaging and Intervention, Massachusetts General Hospital, Yawkey 6E, 55 Fruit Street, Boston, MA, 02114, USA, mbredella@partners.org.
authors.forename: Miriam A
authors.initials: MA
authors.lastname: Bredella
authors.forename: Debora C
authors.initials: DC
authors.lastname: Azevedo
authors.forename: Adriana L
authors.initials: AL
authors.lastname: Oliveira
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Simeone
authors.forename: Connie Y
authors.initials: CY
authors.lastname: Chang
authors.forename: Allston J
authors.initials: AJ
authors.lastname: Stubbs
authors.forename: Martin
authors.initials: M
authors.lastname: Torriani
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks / Q000473:pathology*; D005260:Female; D057925:Femoracetabular Impingement / Q000473:pathology*; D005272:Femur Neck / Q000473:pathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007512:Ischium / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult