Character's direction taken from JointOrientation

Hello! I'm making a VR Game with Kinect v2, Oculus Rift DK2 and Unity5.

Here's my problem: Until now, the direction of my player was taken from the Oculus Rift Direction (From the left eye anchor like this : lEA.transform.forward). Now, I need the player's direction in the game to be the same of the spineBase Joint. So, the idea is that the player should change the walking Direction only if the whole body is rotating, not if only the head is rotating. The SpineBase JointOrientations gives me a Windows.Kinect.Vector4 Object, how can I use it to extract the proper direction? I tried to look, but I can't undersand how to interpreter the Vector4.

Thanks!