Anu Obaro MBBS, Presenter: Nothing to Disclose

Janani Kumaraguru MBBS, Abstract Co-Author: Nothing to Disclose

Kosta Tsitskaris, Abstract Co-Author: Nothing to Disclose

Patrick Li, Abstract Co-Author: Nothing to Disclose

Lisa Marie Meacock MBBS, Abstract Co-Author: Nothing to Disclose

David Andrew Elias MBBS, Abstract Co-Author: Nothing to Disclose

1. To measure the prevalence of  cam-type femoroacetabular impingement morphology in a randomly selected group of young adults with no evidence of preexisting hip disease 2. To determine whether an abnormal alpha angle is associated with reduced hip function scores.  

A retrospective review was made of patients who underwent abdomino-pelvic CT for abdominal trauma or non specific abdominal pain at our institution between August and December 2008 . Inclusion criteria were: age of less than 40 years, no previous hip pathology, no CT evidence of previous hip surgery, hip trauma, post-traumatic deformity or arthropathy. CT scans were reformatted as a rotation around the long axis of the femoral neck from two millimeter axial images through the hips performed on a soft tissue algorithm with bone windows. The alpha angle was measured at the antero-superior quadrant of the femoral neck. An alpha angle of >55° was considered positive for cam morphology. Inter and intra-rater variability of alpha angle measurements was assessed by repeated measurements on a random selection of 18 cases by 2 readers performed twice 4 weeks apart. Questionnaires were sent to subjects to determine current hip function using the Non-Arthritic Hip Score and the University of California Los Angeles activity score.  

45 patients were included (24F; 21M, mean age 33 yrs, range 20-40). 20% (9) of the patients had a right hip and 17% (8) a left hip with cam morphology. 24% (5) of male patients and 17% (4) of female patients had a right hip and 19% (4) of male and 17% (4) of female patients had a left hip with cam morphology. Patient reported functional outcomes between individuals with small alpha angles (≤55º) and large alpha angles (>55º) were compared. No difference between the two groups was identified for any of the scores at every location (p>0.05). The inter-rater and intra-rater agreements were excellent (kappa 0.77 to 1.0 and 0.86 to 1.0 respectively).

Our study demonstrated a significant prevalence of an alpha angle >55º in the general population.The presence of an alpha angle >550is not correlated with adverse hip function scores.

Cam morphology of the femoral neck is commonly seen in young adults and does not necessarily indicate adverse hip function or symptomatology.

Obaro, A, Kumaraguru, J, Tsitskaris, K, Li, P, Meacock, L, Elias, D, The Prevalence of Cam-type Femoroacetabular Deformity and the Significance of a Large Alpha Angle.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11007982.html