The prevalence of cam-type femoroacetabular deformity in asymptomatic adults

J Bone Joint Surg Br. 2011 Oct;93(10):1303-7. doi: 10.1302/0301-620X.93B10.26433.


We performed a retrospective examination of the anteroposterior pelvic CT scout views of 419 randomly selected patients between April 2004 and August 2009 in order to determine the prevalence of cam-type femoroacetabular deformity in the asymptomatic population. The CT scans had all been undertaken for conditions unrelated to disorders of the hip. The frequency of cam-type femoroacetabular deformity was assessed by measuring the α-angle of each hip on the anteroposterior images. The α-angles were classified according to the Copenhagen Osteoarthritis Study. Among 215 male hips (108 patients) the mean α-angle was 59.12° (37.75° to 103.50°). Of these, a total of 30 hips (13.95%) were defined as pathological, 32 (14.88%) as borderline and 153 (71.16%) as normal. Among 540 female hips (272 patients) the mean α-angle was 45.47° (34.75° to 87.00°), with 30 hips (5.56%) defined as pathological, 33 (6.11%) as borderline and 477 (88.33%) as normal. It appears that the cam-type femoroacetabular deformity is not rare among the asymptomatic population. These anatomical abnormalities, as determined by an increased α-angle, appear to be twice as frequent in men as in women. Although an association between osteoarthritis and femoroacetabular impingement is believed to exist, a long-term epidemiological study is needed to determine the natural history of these anatomical abnormalities.

MeSH terms

  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Female
  • Femoracetabular Impingement / diagnostic imaging
  • Femoracetabular Impingement / epidemiology*
  • Femoracetabular Impingement / pathology
  • Hip Joint / diagnostic imaging
  • Humans
  • Male
  • Middle Aged
  • Pennsylvania / epidemiology
  • Prevalence
  • Retrospective Studies
  • Tomography, X-Ray Computed