Fatma Bilge Ergen MD, Presenter: Nothing to Disclose

Sureyya Vudali MD, Abstract Co-Author: Nothing to Disclose

Eser Sanverdi MD, Abstract Co-Author: Nothing to Disclose

Anil Dolgun, Abstract Co-Author: Nothing to Disclose

Ustun Aydingoz MD, Abstract Co-Author: Speaker, Abbott Laboratories Speaker, Merck & Co, Inc

The purpose of this study was to compare axial oblique and radial alpha angle (AA) measurements and search for the prevalence of cam and pincer morphology in asymptomatic individuals with a negative impingement test.

Sixty-eight consecutive patients (131 hips) aged between 18−46 years (mean, 33) who underwent abdominopelvic CT between April−September 2010 for a variety of reasons other than hip problems and who agreed to participate in this study constituted the patient population. Patients who claimed to have had hip and/or vertebral disorders including pain and previous surgery and who had a positive femoroacetabular impingement (FAI) test were excluded. Alpha angle measurements from the axial oblique reformatted images and radial reformat-based AA (A1–A7; A1, anterior; A7, superior portion of femoral head), femoral head-neck offset (FHNO), and central edge angle (CEA), acetabular version angle (AV) measurements were done. Paired sample t- test was used for the comparison of axial oblique and radial AAs.

The mean AA on axial oblique images was 41.10° (SD±4.44) whereas radial AAs ranged from 41.64° (SD±4.23) to 48.13° (SD±4.63). AA measurements on radial reformats were higher than on axial oblique reformats, and the difference was statistically significant (P<0.001). The maximal radial AA values were measured on A5 and A6. Overall prevalence of cam morphology (increased radial AA, decreased FHNO) and pincer morphology (increased CEA, decreased AV) were 19.0%, 26.8%, 25.8%, and 10.2% of the hips, respectively. Moderate to very strong (r= 0.65–0.94) intraobserver and moderate to high (r=0.537–0.877) interobserver correlation was found for AA measurements (P<0.001).

In asymptomatic population, the presence of higher AA values in the anterosuperior portion of femoral head on the radial—compared to the axial oblique—reformatted CT images is not an infrequent finding. Presence of cam and pincer morphology in patients with clinically negative impingement test in asymptomatic persons supports the concept that the elevated AA in isolation is not necessarily diagnostic for FAI, and other morphologic measurements should be carefully considered along with clinical symptoms, physical examination, and other radiologic findings including cartilage damage and labral tears.

Presence of cam and pincer morphology should be assesed cautiolsly in asymptomatic, FAI test negative population.

Ergen, F, Vudali, S, Sanverdi, E, Dolgun, A, Aydingoz, U, Computed Tomography Assessment of Asymptomatic Hip Joints in Relation to Femoroasetabular Impingement.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11012283.html