title: Radiographic features associated with differing impinging hip morphologies with special attention to coxa profunda.
abstract: BACKGROUND
  Combined with clinical examination and MRI, radiographs have been mainstays in the management femoroacetabular impingement (FAI). Because hip morphology often portends intraoperative damage, radiographic features should inform surgical management.
  
  
  OBJECTIVE
  We determined (1) the radiographic features of the various hip morphologies; (2) the prevalence of radiographic coxa profunda in each group; (3) the radiographic differences between hips with and without coxa profunda; and (4) its sensitivity and specificity as a measure of global acetabular overcoverage.
  
  
  METHODS
  We reviewed preoperative radiographs and operative notes of 144 hips that underwent surgical dislocation and correction for FAI between August 2002 and February 2011. Hips were divided into four FAI subtypes by radiographic analysis (cam, global overcoverage, retroversion, and combined) and three subtypes (cam, pincer, or combined) by intraarticular pathology. Standard radiographic measurements were performed, and we introduce a novel measurement that assesses femoral head coverage.
  
  
  RESULTS
  We found differences in median Angle of Sharp, femoral head-neck angle, and median roof length (and its subset) among the FAI morphologies. The prevalence of radiographic coxa profunda was 48% in cam hips, 85% in global overcoverage hips, 66% in retroverted hips, and 32% in combined hips. The sensitivity and specificity of radiographic coxa profunda as a measure of global overcoverage was 75% (95% CI, 0.62-0.85) and 62% (95% CI, 0.51-0.73), respectively.
  
  
  CONCLUSIONS
  We found major differences in radiographic measurements between FAI morphologies. Radiographic coxa profunda was poorly specific for global overcoverage. Measurement of roof length and ratio should be used to determine the morphology of the impinging hip.
  
  
  METHODS
  Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopedics, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
authors.forename: Gregory
authors.initials: G
authors.lastname: Boone
authors.forename: Michael R
authors.initials: MR
authors.lastname: Pagnotto
authors.forename: Justin A
authors.initials: JA
authors.lastname: Walker
authors.forename: Robert T
authors.initials: RT
authors.lastname: Trousdale
authors.forename: Rafael J
authors.initials: RJ
authors.lastname: Sierra
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging* / Q000601:surgery; D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D016009:Chi-Square Distribution; D005260:Female; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging* / Q000601:surgery; D005270:Femur Head / Q000000981:diagnostic imaging* / Q000601:surgery; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011859:Radiography; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D055815:Young Adult