title: A quantitative method to assess focal acetabular overcoverage resulting from pincer deformity using CT data.
abstract: BACKGROUND
  Current assessment techniques for focal acetabular overcoverage are neither consistent nor quantitatively accurate.
  
  
  OBJECTIVE
  We propose: (1) a method to precisely quantify the amount of focal acetabular overcoverage in a patient's pincer deformity based on CT data; (2) to evaluate the consistency of this method; and (3) to compare the method with conventional radiographic assessments.
  
  
  METHODS
  We developed a method to assess focal acetabular overcoverage using points selected from CT scans along the acetabular rim after realigning the pelvis into a neutral position. Using four resampled and segmented pelvic CT scans of cadaveric specimens with virtually induced impingement, two observers independently tested the algorithm's consistency. Our algorithm assessed the amount of focal acetabular overcoverage using CT data and projected data from reconstructed radiographs.
  
  
  RESULTS
  (1) We successfully showed the feasibility of the software to produce consistent, quantitative measurements. (2) Testing showed the average difference between observers in aligning the pelvis was 0.42°, indicative of a consistent approach. (3) Differences between measurements on three-dimensional (3-D) CT and simulated radiographs were significant.
  
  
  CONCLUSIONS
  The proposed method represents a new avenue in consistently quantifying focal acetabular overcoverage using CT models while correcting for pelvic tilt and rotation. Our analysis confirms AP hip radiograph simulations overestimate the amount of overhanging acetabular rim in a pincer deformity.
  
  
  CONCLUSIONS
  This technique has potential to improve preoperative diagnostic accuracy and enhance surgical planning for correction of a pincer deformity resulting from focal acetabular overcoverage.
authors: Milton S Eisenhower Research Center, The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, 21 N109, Laurel, MD 20723, USA. Ryan.Murphy@jhuapl.edu
authors: Ryan J
authors: RJ
authors: Murphy
authors: Ty K
authors: TK
authors: Subhawong
authors: Avneesh
authors: A
authors: Chhabra
authors: John A
authors: JA
authors: Carrino
authors: Mehran
authors: M
authors: Armand
authors: Marc
authors: M
authors: Hungerford
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging*; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002102:Cadaver; D005240:Feasibility Studies; D005260:Female; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D015588:Observer Variation; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D012984:Software; D014057:Tomography, X-Ray Computed