title: Prevalence of pincer, cam, and combined deformities in Japanese hip joints evaluated with the Japanese Hip Society diagnostic guideline for femoroacetabular impingement: A CT-based study.
abstract: BACKGROUND
  Femoroacetabular impingement (FAI) is thought to be associated with hip osteoarthritis. We investigated the prevalences of radiologic deformities of the pincer, cam, and their combinations in Japanese hip joints using computed tomography (CT) according to the Japanese Hip Society diagnostic guideline for FAI.
  
  
  METHODS
  Multi-slice CT images were evaluated. Pincer deformities were defined as: type 1: center-edge angle (CE) ≥40°; type 2: CE ≥ 30° and acetabular roof obliquity ≤0°; type 3: CE ≥ 25° and retroverted acetabulum. Cam deformities were defined as: type 1: CE ≥ 25°, α-angle ≥55°, and head-neck offset ratio <0.14; type 2: CE ≥ 25°, α-angle ≥55°, and herniation pit positive; type 3: CE ≥ 25°, α-angle ≥55°, and pistol grip deformity positive.
  
  
  RESULTS
  We studied 128 hips. Pincer was detected in 35.9% (type 1, 12.5%; type 2, 18.0%; type 3, 13.3%). Cam was detected in 24.2% (type 1, 23.4%; type 2, 7.8%; type 3, 10.9%). Combined deformities were detected in 10.2%. Type 3 pincer/type 1 cam was the most frequent combined deformity compared with all combined deformities. All of the cam deformities, total combined deformities, and all radiological FAIs appeared significantly more often in men.
  
  
  CONCLUSIONS
  When we used this guideline to diagnose FAI in a Japanese population, radiological FAI was common, and pincer deformities were more common than cam deformities. The most frequent seen pincer, cam, and combined deformities was type 2 pincer, type 1 cam, and the combination of type 3 pincer/type 1 cam, respectively.
authors.affiliation: Department of Orthopedic Surgery, Shiga University of Medical Science, Shiga 520-2192, Japan. Electronic address: tmimura@belle.shiga-med.ac.jp.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Mimura
authors.affiliation: Department of Orthopedic Surgery, Shiga University of Medical Science, Shiga 520-2192, Japan.
authors.forename: Kanji
authors.initials: K
authors.lastname: Mori
authors.affiliation: Department of Orthopedic Surgery, Shiga Medical Center for Children, Shiga 524-0022, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Itakura
authors.affiliation: Department of Orthopedic Surgery, Shiga University of Medical Science, Shiga 520-2192, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Furuya
authors.affiliation: Department of Orthopedic Surgery, Shiga University of Medical Science, Shiga 520-2192, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Kawasaki
authors.affiliation: Department of Orthopedic Surgery, Shiga University of Medical Science, Shiga 520-2192, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Imai
mesh_terms: D000077:Acetabulum / Q000002:abnormalities* / Q000000981:diagnostic imaging; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging* / Q000453:epidemiology* / Q000503:physiopathology; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D021621:Imaging, Three-Dimensional; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D015588:Observer Variation; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000503:physiopathology; D010808:Physical Examination / Q000379:methods; D017410:Practice Guidelines as Topic; D015995:Prevalence; D011379:Prognosis; D016059:Range of Motion, Articular / Q000502:physiology; D018570:Risk Assessment; D012720:Severity of Illness Index; D017678:Sex Distribution; D012955:Societies, Medical / Q000592:standards