title: Prevalence of radiographic parameters predisposing to femoroacetabular impingement in young asymptomatic Chinese and white subjects.
abstract: BACKGROUND
  Osteoarthritis of the hip is five to ten times more common in white people than in Chinese people. Little is known about the true prevalence of femoroacetabular impingement or its role in the development of osteoarthritis in the Chinese population. A cross-sectional study of both white and Chinese asymptomatic individuals was conducted to compare the prevalences of radiographic features posing a risk for femoroacetabular impingement in the two groups. It was hypothesized that that there would be proportional differences in hip anatomy between the white and Asian populations.
  
  
  METHODS
  Pelvic computed tomography scans of 201 subjects (ninety-nine white Belgians and 102 Chinese; 105 men and ninety-six women) without hip pain who were eighteen to forty years of age were assessed. The original axial images were reformatted to three-dimensional pelvic models simulating standardized radiographic views. Ten radiographic parameters predisposing to femoroacetabular impingement were measured: alpha angle, anterior offset ratio, and caput-collum-diaphyseal angle on the femoral side and crossover sign, ischial spine projection, acetabular anteversion angle, center-edge angle, acetabular angle of Sharp, Tönnis angle, and anterior acetabular head index on the acetabular side.
  
  
  RESULTS
  The white subjects had a less spherical femoral head than the Chinese subjects (average alpha angle, 56° compared with 50°; p<0.001). The Chinese subjects had less lateral acetabular coverage than the white subjects, with average center-edge angles of 35° and 39° (p<0.001) and acetabular angles of Sharp of 38° and 36° (p<0.001), respectively. A shallower acetabular configuration was predominantly present in Chinese women.
  
  
  CONCLUSIONS
  Significant differences in hip anatomy were demonstrated between young asymptomatic Chinese and white subjects. However, the absolute size of the observed differences appears to contrast with the reported low prevalence of femoroacetabular impingement in Chinese individuals compared with the high prevalence in white populations.
authors.affiliation: Departments of Orthopaedic Surgery and Traumatology (J.V.H., H.D., C.P., and E.A.A.) and Radiology (W.H.), Ghent University Hospital, De Pintelaan 185, B-9000 Ghent, Belgium. E-mail address for E.A. Audenaert: emmanuel.audenaert@ugent.be.
authors.forename: Jan
authors.initials: J
authors.lastname: Van Houcke
authors.affiliation: Departments of Orthopaedic Surgery and Traumatology (W.P.Y. and C.H.Y.) and Radiology (W.H.L. and C.S.W.), Queen Mary Hospital, University of Hong Kong, 102 Pokfulam Road, Hong Kong, China.
authors.forename: Wan Pan
authors.initials: WP
authors.lastname: Yau
authors.affiliation: Departments of Orthopaedic Surgery and Traumatology (W.P.Y. and C.H.Y.) and Radiology (W.H.L. and C.S.W.), Queen Mary Hospital, University of Hong Kong, 102 Pokfulam Road, Hong Kong, China.
authors.forename: Chun Hoi
authors.initials: CH
authors.lastname: Yan
authors.affiliation: Departments of Orthopaedic Surgery and Traumatology (J.V.H., H.D., C.P., and E.A.A.) and Radiology (W.H.), Ghent University Hospital, De Pintelaan 185, B-9000 Ghent, Belgium. E-mail address for E.A. Audenaert: emmanuel.audenaert@ugent.be.
authors.forename: Wouter
authors.initials: W
authors.lastname: Huysse
authors.affiliation: Departments of Orthopaedic Surgery and Traumatology (J.V.H., H.D., C.P., and E.A.A.) and Radiology (W.H.), Ghent University Hospital, De Pintelaan 185, B-9000 Ghent, Belgium. E-mail address for E.A. Audenaert: emmanuel.audenaert@ugent.be.
authors.forename: Hannes
authors.initials: H
authors.lastname: Dechamps
authors.affiliation: Departments of Orthopaedic Surgery and Traumatology (W.P.Y. and C.H.Y.) and Radiology (W.H.L. and C.S.W.), Queen Mary Hospital, University of Hong Kong, 102 Pokfulam Road, Hong Kong, China.
authors.forename: Wing Hang
authors.initials: WH
authors.lastname: Lau
authors.affiliation: Departments of Orthopaedic Surgery and Traumatology (W.P.Y. and C.H.Y.) and Radiology (W.H.L. and C.S.W.), Queen Mary Hospital, University of Hong Kong, 102 Pokfulam Road, Hong Kong, China.
authors.forename: Chun Sing
authors.initials: CS
authors.lastname: Wong
authors.affiliation: Departments of Orthopaedic Surgery and Traumatology (J.V.H., H.D., C.P., and E.A.A.) and Radiology (W.H.), Ghent University Hospital, De Pintelaan 185, B-9000 Ghent, Belgium. E-mail address for E.A. Audenaert: emmanuel.audenaert@ugent.be.
authors.forename: Christophe
authors.initials: C
authors.lastname: Pattyn
authors.affiliation: Departments of Orthopaedic Surgery and Traumatology (J.V.H., H.D., C.P., and E.A.A.) and Radiology (W.H.), Ghent University Hospital, De Pintelaan 185, B-9000 Ghent, Belgium. E-mail address for E.A. Audenaert: emmanuel.audenaert@ugent.be.
authors.forename: Emmanuel Albert
authors.initials: EA
authors.lastname: Audenaert
mesh_terms: D000077:Acetabulum / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D000293:Adolescent; D000328:Adult; D044466:Asian People; D015984:Causality; D015897:Comorbidity; D003430:Cross-Sectional Studies; D005260:Female; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging* / Q000208:ethnology*; D005270:Femur Head / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D005272:Femur Neck / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D006621:Hip Joint / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D015588:Observer Variation; D010003:Osteoarthritis / Q000000981:diagnostic imaging / Q000453:epidemiology; D010808:Physical Examination; D011446:Prospective Studies; D014057:Tomography, X-Ray Computed; D044465:White People; D055815:Young Adult