title: Radiographic Comparison of Anterior Acetabular Rim Morphology Between Pincer Femoroacetabular Impingement and Control.
abstract: OBJECTIVE
  To define and compare 3 new parameters (anterior rim angle [ARA], anterior wall angle [AWA], and anterior margin ratio [AMR]), in addition to the lateral center-edge angle of Wiberg and the Tönnis angle, for measuring pincer-type femoroacetabular impingement (FAI) in an asymptomatic versus symptomatic FAI population.
  
  
  METHODS
  We reviewed anteroposterior pelvis radiographs of patients verified to have no hip complaints between December 2009 and December 2011. We also reviewed anteroposterior pelvis radiographs of patients who underwent a rim-trimming procedure for pincer FAI between December 2010 and December 2011. Patients aged older than 65 years or younger than 18 years were excluded. Radiographs with a Tönnis grade of 2 or greater were also excluded. For the group of patients with symptomatic hip impingement, radiographs that did not have a crossover sign were excluded. The 2 cohorts were matched for age, sex, and body mass index. Measurements included the Tönnis angle, lateral center-edge angle of Wiberg, ARA, AWA, and AMR. These measurements were compared between the groups.
  
  
  RESULTS
  Seventy-two asymptomatic hips were measured. There were 44 female patients (61%) and 28 male patients (39%), aged 25 to 51 years, in the asymptomatic group. The mean ARA was 88.91° ± 8.06°, the mean AWA was 34.89° ± 8.09°, and the mean AMR was 0.49 ± 0.15. Seventy-two symptomatic hips were measured. There were 40 female patients (56%) and 32 male patients (44%), aged 27 to 58 years, in the symptomatic group. The mean ARA was 82.98° ± 10.82°, the mean AWA was 39.11° ± 9.00°, and the mean AMR was 0.56 ± 0.14. The mean difference in the ARA between asymptomatic patients and symptomatic patients was 5.92° (P = .0001). The mean difference in the AWA was 4.22° (P = .0019). The mean difference in the AMR was 0.07 (P = .0039).
  
  
  CONCLUSIONS
  Our study provides information on several measurements within an asymptomatic cohort and a symptomatic cohort. Although we found statistically significant differences between the 2 populations, the clinical significance remains unknown. We recommend using this asymptomatic population as a guideline for limits on resection of the anterior acetabular rim.
  
  
  METHODS
  Level III, retrospective comparative study.
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.. Electronic address: mdhellman@gmail.com.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Hellman
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Gross
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Michael
authors.initials: M
authors.lastname: Hart
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Ryan
authors.initials: R
authors.lastname: Freeman
authors.affiliation: Department of Orthopaedics, University Hospital, Case Western Reserve University School of Medicine, Cleveland, Ohio, U.S.A.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Salata
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Bush-Joseph
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Shane J
authors.initials: SJ
authors.lastname: Nho
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging*; D000293:Adolescent; D000328:Adult; D000368:Aged; D015992:Body Mass Index; D005260:Female; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging* / Q000601:surgery; D005500:Follow-Up Studies; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000379:methods; D011859:Radiography; D012189:Retrospective Studies; D055815:Young Adult