Re: What is the difference between an annular bulge and a posterior bulge?
I believe you may be confusing the word "anterior" with the word "annular." You can have an annular bulge located in a posterior position.
The annular bulge refers to a bulge in the [B]annulus fibrosus[/B] which is a component of the spinal disc. The annulus fibrosus is the outer rings of the disk, whose main job is to hold in place and contain the center of the disc, the nucleus pulposus. The nucleus is the consistency of gelatin and is under high pressure when we are upright, particularly when sitting. The annulus fibrosus is like a belted radial tire. It is composed of many layers, concentric circles of collagen. This structure makes it very strong and helps to hold in the pressurized contents of the center of the disc, the nucleus. It connects the spinal vertebrae above and below the disc. The annulus keeps the nucleus from herniating or leaking out of the disc by "hydraulically" sealing the nucleus and evenly distributing any pressure and force imposed on the disc.
A patient can have a problem with either of these areas of the disc....Due to injury or aging (which begins in our 20s in the case of the spine), a small tear can form in the annulus. When the gel-like center of the disc pushes through an annular tear, you have a disc herniation. If the tear is large enough and most of the nucleus escapes, the disc becomes flattened and loses its cushioning effect. When the disc bulges rather than herniates, it simply means that the center of the disc, the nucleus, is still intact...and is not leaking. If it is bulging quite a bit, it can press into the nerve, causing pain in the lower back or anywhere along the route of the nerve...often running down the leg.