Perihelion advance of a test particle in the Kerr field.

Here I represent a Perihelion advance of a test particle in the Kerr field. I assume that the spin of the central body to be very small and planar motion occurs only in the equatorial plane. I find some physical picture which is different from the case of Schwarzschild field and can recover the picture for Schwarzschild field. We use perturbation method to solve the equation of motion.