The Malleolar Valgus Index (MVI) is a static measurement taken with a flatbed computer scanner. An MVI value is helpful in catogorizing the structure of a foot along a spectrum containing planus (flat-foot), rectus (ideally-aligned), and cavus (high-arched). The MVI reference values for rectus and planus are 7.31 and 17.88 respectively. To make an MVI measurement a plexiglass platform is placed over a scanner bed and a custom-made MVI jig is fitted to the medial malleolus and lateral malleolus (the ankle bones)--as shown above. A scan of the foot is then made in grayscale and posterized to 8 levels which allows for a better view of the foot's contact with the ground. The scan is then printed and measurements are made to determine the following.
The equation to determine MVI value is as follows:
MVI=[BC / (ML-MOV)]*100
ML: Length between the lateral jig marker and the medial jig marker
BC: Length between the foot bisection line and the midpoint of the malleolar bisection line (ML). The foot bisection line is determined by finding the midpoints of the lines A1-A2 (the most anterior border) and P1-P2 (the most posterior border). These two lines are drawn at right angles to the medial border line and end at the lateral border line.
MOV: Constant measuring the distance between the jig and the medial malleolus and lateral malleolus.