Radiographic Comparison of Anterior Acetabular Rim Morphology Between Pincer Femoroacetabular Impingement and Control

Arthroscopy. 2016 Mar;32(3):468-72. doi: 10.1016/j.arthro.2015.08.035. Epub 2015 Oct 30.


Purpose: 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.

Level of evidence: Level III, retrospective comparative study.

Publication types

  • Comparative Study

MeSH terms

  • Acetabulum / diagnostic imaging*
  • Adolescent
  • Adult
  • Aged
  • Body Mass Index
  • Female
  • Femoracetabular Impingement / diagnostic imaging*
  • Femoracetabular Impingement / surgery
  • Follow-Up Studies
  • Hip Joint / diagnostic imaging*
  • Hip Joint / surgery
  • Humans
  • Male
  • Middle Aged
  • Orthopedic Procedures / methods
  • Radiography
  • Retrospective Studies
  • Young Adult