Femoroacetabular impingement - mixed-type

Case contributed by Mostafa El-Feky
Diagnosis almost certain


Painful left hip.

Patient Data

Age: 30 years
Gender: Male



An osseous bump is noted at the femoral head-neck junctions, and short femoral neck bilaterally. 

There is a crossover sign on both sides, more apparent on the right side, which indicates acetabular retroversion.

Subtle asphericity of the femoral head bilaterally. An osseous bump is noted at the femoral head-neck junctions, and short femoral neck bilaterally. 

Abnormal linear T2 hyperintense signal noted at the anterosuperior labrum, at the labral-chondral transitional zone, on the left side.

Subcortical degenerative cystic changes at the anterosuperior aspect of the left acetabulum.

Normal marrow signal of both femoral heads, no MRI evidence of avascular necrosis.

Annotated image

The lateral center-edge angle (LCEA) is increased on both sides averaging 43º indicated acetabular overcoverage (normal range 25-39º).

Measurement of alpha angel through oblique MPR reconstruction sections at a level parallel to femoral neck revealed increased angel more than 70º  (normal value 55º).

Case Discussion

Features are in keeping with bilateral femoroacetabular impingement (mixed-type), with associated labral tear. The crossover sign has been implicated in pincer-type femoroacetabular impingement and is thought to be a predisposing factor for osteoarthritis. Most cases of FAI are a combination of both cam and pincer-type mechanisms, with cam-type more predominate.

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