title: Femoroacetabular Impingement and Pelvic Incidence: Radiographic Comparison to an Asymptomatic Control.
abstract: OBJECTIVE
  To investigate whether pelvic incidence (PI) in patients with symptomatic femoroacetabular impingement was different from that in a normal population.
  
  
  METHODS
  Retrospective analysis of 30 consecutive female and 30 consecutive male patients with computed tomography scans who underwent hip arthroscopy for FAI. PI was measured using scout lateral radiographs. The center-edge angle (CEA), acetabular version, and α angle were also measured. Each patient was subcategorized as having a cam-type deformity (α angle >55°), a deep socket deformity (CEA >39°), and/or a retroverted acetabulum (acetabular anteversion <15°). Our group and subgroups were compared with a historical control group from a previously published study of 300 volunteers. Each group was compared using a Student t test.
  
  
  RESULTS
  Our mean PI was 49.31° ± 12.34° (range, 28.4°-79.5°), less than the asymptomatic historical control (n = 300) with a mean PI of 55.0° ± 10.6° (range, 33°-82°) (P < .001). The subgroups for cam deformity, deep socket deformity, and acetabular retroversion have a mean PI of 48.89° ± 11.81°, 38.30° ± 7.56°, and 44.93° ± 11.32°, respectively. All had a significantly lower PI than the historical control (P < .001, P < .001, P < .001, respectively).
  
  
  CONCLUSIONS
  We conclude that patients presenting with FAI may have a lower PI than the general population. The clinical significance of a 5.7° difference in PI remains unknown.
  
  
  METHODS
  Level III, retrospective comparative study.
authors.affiliation: Rush University Medical Center, Department of Orthopaedic Surgery, Chicago, Illinois, U.S.A.. Electronic address: mdhellman@gmail.com.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Hellman
authors.affiliation: Rush University Medical Center, Department of Orthopaedic Surgery, Chicago, Illinois, U.S.A.
authors.forename: Bryan D
authors.initials: BD
authors.lastname: Haughom
authors.affiliation: Rush University Medical Center, Department of Orthopaedic Surgery, Chicago, Illinois, U.S.A.
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Brown
authors.affiliation: Rush University Medical Center, Department of Orthopaedic Surgery, Chicago, Illinois, U.S.A.
authors.forename: Yale A
authors.initials: YA
authors.lastname: Fillingham
authors.affiliation: Steadman Clinic and Steadman Philippon Research Institute, Vail, Colorado, U.S.A.
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Philippon
authors.affiliation: Rush University Medical Center, Department of Orthopaedic Surgery, Chicago, Illinois, U.S.A.
authors.forename: Shane J
authors.initials: SJ
authors.lastname: Nho
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000502:physiology; D065386:Historically Controlled Study; D006801:Humans; D008297:Male; D008875:Middle Aged; D010384:Pelvic Bones / Q000000981:diagnostic imaging* / Q000502:physiology; D004856:Postural Balance / Q000502:physiology*; D012189:Retrospective Studies; D055815:Young Adult