What alpha angle defines cam morphology?

Alpha angle >55-60 degrees on radial MRI at 1 o'clock position (Clohisy) indicates cam-type FAI. Alpha angle >80 degrees is associated with labral tears in 70-80% of cases. Measurement varies by imaging plane; standardization is important.

What is the crossover sign for pincer FAI?

Crossover sign on AP pelvis radiograph: the anterior acetabular wall crosses in front of the posterior wall. Combined with coxa profunda (medial wall below ilioischial line) or protrusio acetabuli indicates pincer-type over-coverage.

What is the outcome of hip arthroscopy for FAI?

Hip arthroscopy for FAI with labral repair achieves iHOT-33 improvement of 25-35 points at 2 years. Cam resection alone (osteochondroplasty) achieves alpha angle normalization in >90%. Conversion to THA at 5 years: 5-10% in appropriately selected patients.

Femoroacetabular Impingement Alpha Angle and Crossover Sign

Calculate the alpha angle from MRI/CT/radiograph for cam-type femoroacetabular impingement (FAI) diagnosis. Alpha angle >55 degrees (Clohisy) or >60 degrees (Netzli) indicates pathological cam morphology. Crossover sign detects pincer morphology.

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Frequently Asked Questions

What alpha angle defines cam morphology?

What is the crossover sign for pincer FAI?

What is the outcome of hip arthroscopy for FAI?