Selecting intersection point of the major axis with a point on a boundary image

Hi, I've attached a boundary image of a hand and I'm looking to select the first intersection point of the major axis with the wrist line (example shown in the wristref picture). I then want to calculate the euclidean distance of every other point on the boundary from this reference point. The reason I'm doing this is because I'm looking for the points on the boundary that correspond to the peaks of the fingers and the valleys in between fingers. How would I go about finding the major axis of a boundary image of a hand and then finding where this axis intersects with the bottom of the palm/wrist line? If anyone has any better solutions for finding the boundary points corresponding to peaks/valleys of the fingers and thumb I would also be interested in hearing them.