Migration Percentage (MP) of the Femoral Head

 

Parameters:

(1) total width of the femoral head in mm

(2) width of the femoral head lateral to Perkin’s line in mm

 

Perkin’s line is a vertical line that

(1) passes through the most lateral aspect of the acetabular roof

(2) is perpendicular to Hilgenreiner’s line (a horizontal line that passes through the superior aspect of the triradiate cartilages

 

migration percentage =

= (width of femoral head lateral to Perkin’s line) / (total width) * 100%

 

Interpretation:

• A migration percentage > 33% is an indication for hip reconstructive surgery in a child with cerebral palsy.and spastic hip instability.