Cam-type deformities are a classical feature of femoroacetabular impingement (FAI). However, in many asymptomatic healthy individuals the morphology of the proximal femur looks similar to a cam-type deformity.

The most common method for quantifying cam-type deformities is the alpha angle, but it was shown that this is not an accurate method for diagnosing FAI.

There are concerns about overdiagnosis and overtreatment of patients with suspected FAI – so an accurate diagnosis of the hallmarks of FAI is important. A recent study set out to evaluate whether alternative measurement methods might be more accurate for assessing cam-type deformities [1]: This study found that alternative measurements (femoral distance, offset) showed similar results to the alpha angle in assessing cam-type deformities: A substantial overlap was present between healthy individuals and FAI patients, indicating that so far no reliable method is available for diagnosing cam-type deformities.

[1] Ehrmann C, Rosskopf AB, Pfirrmann CW, Sutter R.
“Beyond the alpha angle: Alternative measurements for quantifying cam-type deformities in femoroacetabular impingement.”

J Magn Reson Imaging. 2015 Feb 2. doi: 10.1002/jmri.24861 (link)

Offset and Femoral Distance measurement

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