title: The False-Profile View May Be Used to Identify Cam Morphology.
abstract: OBJECTIVE
  To identify the accuracy of measuring the alpha angle on the false-profile, anteroposterior (AP), and 90° Dunn lateral views of the hip as compared with computed tomography (CT) scan findings.
  
  
  METHODS
  Forty patients were needed to have power greater than 80%. Forty-five consecutive patients undergoing hip arthroscopy were retrospectively reviewed with preoperative radial oblique CT reformatted scans and plain radiographs. Alpha angles were measured on plain radiographs (AP, 90° Dunn lateral, and false profile) and CT reformatted views. Abnormal alpha angles were considered greater than 50.5°. Two orthopaedic surgeons independently measured the images, and the results were compared between imaging modalities.
  
  
  RESULTS
  The false-profile view was 60% sensitive and 89.0% specific for diagnosing cam deformities of the hip. All radiographs combined were 86% sensitive and 75% specific for diagnosing cam deformities. The false-profile view most strongly correlated with the 2-o'clock (R = 0.746, P = .001) and 3-o'clock (R = 0.698, P < .0001) positions. An intraclass correlation coefficient of 0.81 was found for measurement of the alpha angle on the false-profile view.
  
  
  CONCLUSIONS
  This study has proved that the false-profile view effectively characterizes cam deformity, especially anterior deformity at the 3-o'clock position. Measuring the alpha angle on the false-profile view appears to be reproducible. The false-profile view along with standing AP pelvis and 90° Dunn lateral views of the hip comprises a good screening radiographic series for patients presenting with symptoms of femoroacetabular impingement.
  
  
  METHODS
  Level III, diagnostic study.
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.. Electronic address: mdhellman@gmail.com.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Hellman
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Randy
authors.initials: R
authors.lastname: Mascarenhas
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Anil
authors.initials: A
authors.lastname: Gupta
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Yale
authors.initials: Y
authors.lastname: Fillingham
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Bryan D
authors.initials: BD
authors.lastname: Haughom
authors.affiliation: Department of Orthopedic Surgery, University Hospitals Case Medical Center, Cleveland, Ohio, U.S.A.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Salata
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Shane J
authors.initials: SJ
authors.lastname: Nho
mesh_terms: D000293:Adolescent; D000328:Adult; D001182:Arthroscopy; D005189:False Positive Reactions; D005260:Female; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging* / Q000601:surgery; D005270:Femur Head / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D055815:Young Adult