function measureRetroversion(obj)
  % Glenoid retroversion is the angle between the glenoid postero-anterior line 
  % and the line perpendicular to the Friedman's line that goes through the most 
  % anterior glenoid rim point.
  %
  % obj.measurePosteroAnteriorLine() and obj.scapula.measureFriedmansLine() must
  % have been run before measuring the glenoid retroversion.
  FL = obj.scapula.friedmansLine;
  anteriorRimPoint = obj.getAnatomicalExtremeRimPoints().anterior;
  FLToAnteriorRimPoint = FL.orthogonalComplementToPoint(anteriorRimPoint);

  % Lines projection on scapular axial plane.
  IS = Vector([0 0 0], obj.scapula.coordSys.IS);
  FLToAnteriorRimPointXZ = IS.orthogonalComplementToPoint(FLToAnteriorRimPoint.vector);
  glenoidPosteroAnteriorLineXZ = IS.orthogonalComplementToPoint(obj.posteroAnteriorLine.vector);

  retroversionRotation = vrrotvec(FLToAnteriorRimPointXZ.vector, glenoidPosteroAnteriorLineXZ.vector);
  obj.retroversion = -sign(dot(IS.vector,retroversionRotation(1:3)))*rad2deg(retroversionRotation(4));
end