Femoro-acetabular impingement (FAI) CAM type: with alpha angle measurements

Case contributed by Dr Domenico Nicoletti


Pain in both hips.

Patient Data

Age: 50
Gender: Male

Bilaterally there is appreciable bone production between the femoral head and neck (bump) with loss of sphericity.

Osteoarthritis with joint space narrowing and osteophytes in the lower margin level of the head.

The angle alpha is 85 ° to the right and 84 ° to the left.

Case Discussion

To calculate the alpha angle first find the center of the epiphysis then track axis through femoral neck to the center of the epiphysis, and then the circumference of the curvature radius at the point where the epiphysis profile moves away from the circle to become neck.

Alpha angle in the normal hip is < 50 °. In cam-type FAI the alpha angle is >50 °.

PlayAdd to Share

Case information

rID: 44215
Published: 11th Apr 2016
Last edited: 25th Aug 2019
Inclusion in quiz mode: Included

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.