title: Prevalence of Femoroacetabular Impingement Imaging Findings in Asymptomatic Volunteers: A Systematic Review.
abstract: OBJECTIVE
  The aim of this study was to determine the prevalence of radiographic findings suggestive of femoroacetabular impingement (FAI) in asymptomatic individuals.
  
  
  METHODS
  A systematic review was performed using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies reporting radiographic, computed tomographic, or magnetic resonance imaging (MRI) findings that were suggestive of FAI in asymptomatic volunteers were included. Cam, pincer, and combined pathologic conditions were investigated.
  
  
  RESULTS
  We identified 26 studies for inclusion, comprising 2,114 asymptomatic hips (57.2% men; 42.8% women). The mean participant age was 25.3 ± 1.5 years. The mean alpha angle in asymptomatic hips was 54.1° ± 5.1°. The prevalence of an asymptomatic cam deformity was 37% (range, 7% to 100% between studies)-54.8% in athletes versus 23.1% in the general population. Of the 17 studies that measured alpha angles, 9 used MRI and 9 used radiography (1 study used both). The mean lateral and anterior center edge angles (CEAs) were 31.2° and 30°, respectively. The prevalence of asymptomatic hips with pincer deformity was 67% (range 61% to 76% between studies). Pincer deformity was poorly defined (4 studies [15%]; focal anterior overcoverage, acetabular retroversion, abnormal CEA or acetabular index, coxa profunda, acetabular protrusio, ischial spine sign, crossover sign, and posterior wall sign). Only 7 studies reported on labral injury, which was found on MRI without intra-articular contrast in 68.1% of hips.
  
  
  CONCLUSIONS
  FAI morphologic features and labral injuries are common in asymptomatic patients. Clinical decision making should carefully analyze the association of patient history and physical examination with radiographic imaging.
  
  
  METHODS
  Level IV, systematic review if Level II-IV studies.
authors: Hip Preservation Center, Division of Sports Medicine, Department of Orthopedic Surgery, Rush University Medical Center, Rush Medical College of Rush University, Chicago, Illinois, U.S.A.. Electronic address: jon.m.frank@gmail.com.
authors: Jonathan M
authors: JM
authors: Frank
authors: Hip Preservation Center, Division of Sports Medicine, Department of Orthopedic Surgery, Rush University Medical Center, Rush Medical College of Rush University, Chicago, Illinois, U.S.A.
authors: Joshua D
authors: JD
authors: Harris
authors: Hip Preservation Center, Division of Sports Medicine, Department of Orthopedic Surgery, Rush University Medical Center, Rush Medical College of Rush University, Chicago, Illinois, U.S.A.
authors: Brandon J
authors: BJ
authors: Erickson
authors: Hip Preservation Center, Division of Sports Medicine, Department of Orthopedic Surgery, Rush University Medical Center, Rush Medical College of Rush University, Chicago, Illinois, U.S.A.
authors: William
authors: W
authors: Slikker
authors: Hip Preservation Center, Division of Sports Medicine, Department of Orthopedic Surgery, Rush University Medical Center, Rush Medical College of Rush University, Chicago, Illinois, U.S.A.
authors: Charles A
authors: CA
authors: Bush-Joseph
authors: Hip Preservation Center, Division of Sports Medicine, Department of Orthopedic Surgery, Rush University Medical Center, Rush Medical College of Rush University, Chicago, Illinois, U.S.A.
authors: Michael J
authors: MJ
authors: Salata
authors: Hip Preservation Center, Division of Sports Medicine, Department of Orthopedic Surgery, Rush University Medical Center, Rush Medical College of Rush University, Chicago, Illinois, U.S.A.
authors: Shane J
authors: SJ
authors: Nho
mesh_terms: D003952:Diagnostic Imaging; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging* / Q000453:epidemiology; D014943:Global Health; D064368:Healthy Volunteers; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006801:Humans; D008279:Magnetic Resonance Imaging; D015995:Prevalence; D014057:Tomography, X-Ray Computed