there are contained herniations and non-contained. the non-contained are when the nucleus pulposus escapes the confines of the anulus due to a tear or rupture in the outer rings of the anulus.
i am not aware of any evidence that a vaccum effect (if you can point me to the research I would like to see it) can pull the nuclear material, which is seen as a foreign substance by the body and is highly irritating to local tissues, back into the center of the disc. what basically commences is an inflammatory response where macrophages scour the nuclear material from the area. that process takes several months to complete. one of the benefits of traction is it helps circulation into the area which will enhance the body's clean-up efforts.
the injections of corticosteroids may help relieve pain in the short-term but has little effect on the long-term outcome. repeated injections of corticosteroids have also been linked to localized osteoporosis.