title: Evaluation of the magnitude and location of Cam deformity using three dimensional CT analysis.
abstract: The cam-type deformity in femoroacetabular impingement is a 3D deformity. Single measurements using radiographs, CT or MRI may not provide a true estimate of the magnitude of the deformity. We performed an analysis of the size and location of measurements of the alpha angle (α°) using a CT technique which could be applied to the 3D reconstructions of the hip. Analysis was undertaken in 42 patients (57 hips; 24 men and 18 women; mean age 38 years (16 to 58)) who had symptoms of femoroacetabular impingement related to a cam-type abnormality. An α° of > 50° was considered a significant indicator of cam-type impingement. Measurements of the α° were made at different points around the femoral head/neck junction at intervals of 30°: starting at the nine o'clock (posterior), ten, eleven and twelve o'clock (superior), one, two and ending at three o'clock (anterior) position. The mean maximum increased α° was 64.6° (50.8° to 86°). The two o'clock position was the most common point to find an increased α° (53 hips; 93%), followed by one o'clock (48 hips; 84%). The largest α° for each hip was found most frequently at the two o'clock position (46%), followed by the one o'clock position (39%). Generally, raised α angles extend over three segments of the clock face. Single measurements of the α°, whether pre- or post-operative, should be viewed with caution as they may not be representative of the true size of the deformity and not define whether adequate correction has been achieved following surgery.
authors.affiliation: University College London Hospitals, 250 Euston Rd, London, NW1 2PG, UK.
authors.forename: O
authors.initials: O
authors.lastname: Khan
authors.affiliation: University College London Hospitals, 250 Euston Rd, London, NW1 2PG, UK.
authors.forename: J
authors.initials: J
authors.lastname: Witt
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging*; D005270:Femur Head / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D055815:Young Adult
keywords: Alpha angle; CT; Femoroacetabular impingement; Imaging