Lateral center-edge angle

Last revised by Yuranga Weerakkody on 31 Dec 2023

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

The lateral center-edge angle has primarily been described in assessing for acetabular dysplasia, but can also be used in femoroacetabular impingement (FAI).

The lateral center-edge angle was first described by Wiberg and 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 9

In a modification by Ogata et al., the second line runs to the lateral edge of the acetabular sourcil 6, which is proposed to be a more functional method given that this measurement includes the weight-bearing portion of the acetabulum 8.

As expected, lateral acetabular rim and acetabular sourcil measurements show significant differences, which need to be taken into account 7. The lateral acetabular rim method overestimates coverage by ~4° compared to the acetabular sourcil method as it includes non-weightbearing bone that forms part of the labral base 8.

  • cannot be measured in patients with abnormal femoral heads due to previous injury or osteonecrosis 5

Gunnar Wiberg (1902-1988), a Swedish orthopedic surgeon, first described the lateral center-edge angle in 1939 9,10

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