title: The effect of acetabular rim recession on anterior acetabular coverage: a cadaveric study using the false-profile radiograph.
abstract: BACKGROUND
  The majority of rim recession for femoroacetabular impingement (FAI) is performed anteriorly and has traditionally been assessed by the lateral center-edge (CE) angle, which correlates most closely with lateral coverage. The radiographic false-profile view permits measurement of anterior coverage via the anterior CE angle and more closely correlates with anterior coverage.
  
  
  OBJECTIVE
  To answer the following questions: (1) How does incremental anterior rim recession change lateral and anterior CE angles? and (2) Can these changes be predicted by a formula?
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Twelve cadaveric hips were dissected free of soft tissue to expose the anterior acetabular rim. Incremental resections of 2.5 mm (range, 0-10 mm) were performed from the 12- to 3-o'clock position using a Dremel rotary tool. Anteroposterior hip and false-profile radiographs were obtained at each interval using a fluoroscopic C-arm. The lateral and anterior CE angles were measured by 3 orthopaedic surgeons.
  
  
  RESULTS
  The average preresection lateral CE angle was 35.1°, and the mean decrease in lateral CE angle from 0 to 10 mm was 9.9°; the average preresection anterior CE angle was 38.4° and the mean decrease in anterior CE angle from 0 to 10 mm was 18.2°. The anterior CE angle decreased by a factor of 1.9 when compared with the lateral CE angle (P = 2 × 10(-7)). The lateral CE angle decreased by approximately 1° (1.0°) per millimeter of rim recessed. The anterior CE angle decreased by approximately 2° (1.8°) per millimeter of rim recessed.
  
  
  CONCLUSIONS
  The lateral CE angle should not be extrapolated to reflect anterior acetabular coverage. The anterior CE angle is a superior marker and predictably decreases with rim recession at double the rate of the lateral CE angle.
  
  
  CONCLUSIONS
  The false-profile view is recommended in the perioperative workup for all patients undergoing arthroscopic treatment of pincer impingement.
authors.affiliation: Department of Orthopaedic Surgery, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Kling
authors.affiliation: Department of Orthopaedic Surgery, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA Michael.karns@uhhospitals.org.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Karns
authors.affiliation: Department of Orthopaedic Surgery, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Gebhart
authors.affiliation: Department of Orthopaedic Surgery, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
authors.forename: Christos
authors.initials: C
authors.lastname: Kosmas
authors.affiliation: Department of Orthopaedic Surgery, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Robbin
authors.affiliation: Rush University Medical Center, Chicago, Illinois, USA.
authors.forename: Shane J
authors.initials: SJ
authors.lastname: Nho
authors.affiliation: Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Asheesh
authors.initials: A
authors.lastname: Bedi
authors.affiliation: Department of Orthopaedic Surgery, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Salata
mesh_terms: D002102:Cadaver; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D005471:Fluoroscopy / Q000379:methods*; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D006801:Humans; D010820:Physicians
keywords: femoroacetabular impingement; hip arthroscopy; imaging; rim recession