Lateral center-edge angle

Last revised by Dr Matt Adams on 23 Apr 2021

The lateral center-edge angle is a radiographic measurement of femoral head bony coverage by the acetabulum. It has since been shown superior to the extrusion index in measuring femoral head undercoverage. 

It has primarily been described in assessing for acetabular dysplasia, but can also be used in femoroacetabular impingement.

This angle is calculated on AP pelvic radiographs by drawing a best fit circle for the inferior and medial margins femoral head. The angle is then measured between two lines drawn from the center of the circle, one running vertically along the longitudinal axis of the pelvis and the other to the lateral acetabular rim. 

In the modification by Ogata the second line runs to the lateral edge of the acetabular sourcil 6,7.

Values between 25° and 39° are considered within the normal range 1.

As expected, lateral bony rim and acetabular sourcil measurements show significant differences, which needs to be taken into account 7

  • >39°: pincer type impingement
  • cannot be measured in patients with abnormal femoral heads due to previous injury or avascular necrosis 5

It was originally described by Wiberg in 1939 ref

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